Showing posts with label Man Made Fiber. Show all posts
Showing posts with label Man Made Fiber. Show all posts
20 December 2012
Acrylic Fiber
A
manufactured fiber in which the fiber-forming substance is any long
chain synthetic polymer composed of at least 85% by weight of
acrylonitrile units [-CH2-CH(CN)-] (FTC definition). Acrylic fibers are
produced by two basic methods of spinning (extrusion), dry and wet. In
the dry spinning method, material to be spun is dissolved is a solvent.
After extrusion through the spinneret, the solvent is evaporated,
producing continuous filaments which later may be cut into staple, if
desired. In wet spinning, the spinning solution is extruded into a
liquid coagulating bath to form filaments, which are drawn, dried, and processed.
Acrylic fibers are synthetic fibers made from a polymer (polyacrylonitrile) with an average molecular weight of ~100,000, about 1900 monomer units. To be called acrylic in the U.S, the polymer must contain at least 85% acrylonitrile monomer. Typical comonomers are vinyl acetate or methyl acrylate. The Dupont Corporation created the first acrylic fibers in 1941 and trademarked them under the name "Orlon".
liquid coagulating bath to form filaments, which are drawn, dried, and processed.
Acrylic fibers are synthetic fibers made from a polymer (polyacrylonitrile) with an average molecular weight of ~100,000, about 1900 monomer units. To be called acrylic in the U.S, the polymer must contain at least 85% acrylonitrile monomer. Typical comonomers are vinyl acetate or methyl acrylate. The Dupont Corporation created the first acrylic fibers in 1941 and trademarked them under the name "Orlon".
Raw Material
Acrilonitrile is the main main raw material for the manufacture of acrylic fibres. It is made by different methods. In one commercial method, hydrogen cyanide is treated with acetylene:
1st Method
Acetylene + Hydrogen cyanide --> Acrilonitrile
2nd Method
Ethylene--Air Oxidation--> Ethylene oxide + HCN--> Ethylene cyanahydrin--Dehydration at 300 deg C (catalyst)--> Acrylonitrile
Production Process of Acrylic Fiber
The acrylic process is a "one step technology", with the following main characteristics:
In a continuous
polymerisation process, 95% acrylonitrile and 6% methyl acrylate (400
parts) 0.25% aqueous solution of K2S2O8(600 parts), 0.50 % Na2S2O5
solution ( 600 Parts) and 2N sulphuric acid (2.5 Parts) are fed into
the reaction vessel at 52 deg C under nitrogen atmosphere giving a
slurry with 67% polymer. The slurry is continuously withdrawn, filtered
and washed till it is free from salts and dried.
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2nd Method
Ethylene--Air Oxidation--> Ethylene oxide + HCN--> Ethylene cyanahydrin--Dehydration at 300 deg C (catalyst)--> Acrylonitrile
Production Process of Acrylic Fiber
The acrylic process is a "one step technology", with the following main characteristics:
- polymerization in solution
- direct feeding of the dope to spinning
- wet spinning
- DMF as solvent for both polymerization and spinning
 |
| Production Process of Acrylic Fiber |
Acrilonitrile is dry spun. The
material is dissolved in dimethyl formamide, the solution contains
10-20 polymers. It is heated and extruded into a heated spinning cell. A
heated evaporating medium such as air, nitrogen or steam moves counter
current to the travel of filaments and removes the solvent to take it
to a recovery unit. The filaments are hot stretched at 100 to 250 C
depending on the time of contact in the hot zone, to several times
their original length.
Properties of Acrylic Fibers
1.
Acrylic has a warm and dry hand like wool. Its density is 1.17 g/cc as
compared to 1.32 g/cc of wool. It is about 30% bulkier than wool. It
has about 20% greater insulating power than wool.
2. Acrylic has a moisture regain of 1.5-2% at 65% RH and 70 deg F.
3. It has a tenacity of 5 gpd in dry state and 4-8 gpd in wet state.
4. Breaking elongation is 15% ( both states)
5. It has a elastic recovery of 85% after 4% extension when the load is released immediately.
6.
It has a good thermal stability. When exposed to temperatures above
175 deg C for prolonged periods some discolouration takes place.
7. Acrylic shrinks by about 1.5% when treated with boiling water for 30 min.
8.
It has a good resistance to mineral acids. The resistance to weak
alkalies is fairly good, while hot strong alkalies rapidly attack
acrylic.
9. Moths, Mildew and insects do not attack Acrylic.
10. It has an outstanding stability towards commonly bleaching agents.
Uses of Acrylic Fiber
1. Knit Jersey, Sweater, blankets
2. Wrinkle resistant fabrics.
3. Pile and Fleece fabrics
4. Carpets and rugs.
Precaution of Acrylic Fiber
- Wash delicate items by hand in warm water. Static electricity may be reduced by using a fabric softener in every third or fourth washing. Gently squeeze out water, smooth or shake out garment and let dry on a non-rust hanger. (Sweaters, however, should be dried flat.)
- When machine washing, use warm water and add a fabric softener during the final rinse cycle.
- Machine dry at a low temperature setting. Remove garments from dryer as soon as tumbling cycle is completed.
- If ironing is required, use a moderately warm iron. (For specific instructions, refer to garment's sewn-in care label.)
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7 December 2012
Milk Fiber
Milk Fiber:Milk fiber is a blend of casein protein and the chemical acrylonitrile, which is used to make acrylic.
It’s made using a process that is similar to rayon/viscose, but because
it’s a regenerated protein fiber and not a regenerated cellulose fiber,
it reacts like wool. That means that it dyes like wool and even smells
like wool when burned, according to Kiplinger.
 |
| Milk fiber |
Characteristics of Milk Fiber:
According to Euroflax Industries, milk fiber was invented in 1930’s in both Italy and America and was called “milk casein.” Huh. Who knew? And here I thought it was some newfangled invention. But apparently it’s been around for a while. Whoa. For a longwhile! Crazily enough, casein was inventedway before the 1930s – apparently they’ve discovered that many churches from the 14th and 15th centuries were painted with casein-based paints – the colors are still bright and unfaded even to this day! Well, apparently this milk casein stuff is great for paint. But how does that connect with milk fiber?
Apparently “milk casein” fiber was used in many clothing and household items in America and Europe during the 1930s and ’40s, says Joan Kiplinger of Fabrics.net. It was substitute for wool, which was needed by men on the front lines. However, it fell out of use after WWII ended and newer, cheaper synthetics such as nylon grew in popularity. The fiber was blended with other natural fibers and known under the brand names of Aralac, Lanatil and Merinova, for those of you checking your vintage clothing labels. While these brands’ fabrics were very similar to wool and could be dyed by the same processes, apparently there were some flaws with the milk casein fiber – namely, that it was not as strong and firm, nor as elastic as wool, and the fibers mildewed easily when they got damp.
Production Process of Milk Fiber:
Milk protein fiber production line application processing system can not do without the cooperation of the link. Shanghai is home on R & D Technology Co., Ltd. milk silk protein fibers, also engaged in spinning, dyeing and finishing of technical research, raw material quality, technology is complete, customers can better support the promotion of milk fiber.
Milk protein fiber can be used, in theory, cationic dyes, direct dyes, acid dyes, reactive dyes, neutral dyes, generally more than the actual cationic dye and reactive dye used is suitable for pure milk protein fiber and its products, such as staple fiber, yarn line, knitted fabrics, woven fabrics and garments. Period in order to milk protein fiber textiles as an example of pure cationic dyes and reactive dyes on the usage described as follows.
After Treatment of Milk Fiber:
Cationic dyes and finishing the first treatment process, due to temperature and moisture absorption of the products are strong, so do not need special treatment. With 60 ?water, liquid running back 10s, and then the second can of cold wash. In the special white process, the use of prescription and bleaching conditions were as follows: 5% sodium hydrosulfite (95 ?with warm water even after accession); 5% of the standard soap powder (use warm water even after the accession), not alkaline , does not contain brighteners; bath ratio 1:20 ~ 30; temperature of 95 ~ 98 ? time is about 15s ~ 30s, but also according to liquor ratio, equipment and raw materials of different thickness to adjust. Note that, if so special white, raw materials without cooling; If the training is finished, then white, must be 2% to 3% of the HAC, 60 ?water running 5s ~ 10s, cold washed twice, and then softening. Prescription and use of the whitening process conditions: 1.6% cationic brighteners (Dilute with warm water even after accession); 3% HAC (Dilute with warm water even after accession); temperature of 95 ~ 98 ? time of 15s ~ 20s ; bath ratio 1:25 ~ 30. In the dyeing process, the basic cationic dye with the general approach, but not 1227, and NaAc. To liquor ratio 1:25 to 30, for example, dyeing conditions to control the following table. Cleaning, light to be 1 or 2 times the cold wash, cold wash in the dark to be 1 or 2 times and then wash with hot water, 70 ?10s, and finally cold wash 1 or 2 times. In the post-treatment processes, the use of softener 5% to 8%; temperature 45 ~ 50 ? time of 20s or so; bath ratio 1:20 ~ 25.
According to different requirements of customers can choose different softeners, such as the fabric soft, smooth, elastic anti-wrinkle, anti-contamination, etc. when requested, by the production units to decide. In the dehydration process, in order to reduce the discount video, dehydration, slower, time is shorter, usually 1 minute each time, while patients have to row together, try not to let cloth folded. In the drying process, the use of the cage drying temperature of 80 ? 5 ? time is 20s ~ 30s, speed too quickly, after drying grounds lit 12 to 24 hours after the stereotypes. Using rotary drying temperature of 90 ? 5 ? fast speed, the disadvantage is the easy bit like a very light, must be strictly controlled temperature.
In the setting process, the general shape of water rolling open sites, the effect is better than the cylindrical shape. Process parameters are 150 ? 5% overfeed of 10%, the line speed 15m / s, the pressure head of about 4kg. Reactive dyeing of basic aspects of pre-treatment with the former, but if the dye houses using recycled water, pH value may be unstable or reactive groups dealing with different materials, can be the first treatment bath by adding 1% of the HAC, it will give the pH value of the cloth evenly from the inside out, but also conducive to color dyes.
Proven, low temperature dyeing cotton used reactive dyes more suitable, light-colored soda instead of baking soda can be used as dyeing auxiliaries, the amount can be as long as required to achieve the color, the dark can be used for dyeing auxiliary sodium sulfate and soda ash , the amount of cotton fiber dyed with similar.
Uses of Milk or Casein Fiber:
Because of the healthy & bacteriostatic nature of milk Fiber, it is being considered as a perfect material for manufacturing of underwear. As discussed above, milk casein proteins are considered as a main ingredient of milk protein Fiber, which can lubricate the skin. The milk protein contains the natural humectant factor which can help to maintain the skin moisture, to reduce the wrinkles & to smoothen the skin - which may help to realize the people of taking milk bath.
The major usages of milk Fiber are as given below:
- In milk fibre,the natural protein humectant factor is present,which makes the skin delicate and smooth...
- It absorbs moisture very well as it is hygroscopic in nature.
- It is antibacterial and antifungal as amino acids present in the fibre.
- It is glossy and luxurious in appearance,feel and comfortability, just like silk..
- It is very easy to dye and can be dyed under normal temperature.
- It can be blended well with other different fiares,such as tencel,cotton,bamboo,modal fibre.
According to Euroflax Industries, milk fiber was invented in 1930’s in both Italy and America and was called “milk casein.” Huh. Who knew? And here I thought it was some newfangled invention. But apparently it’s been around for a while. Whoa. For a longwhile! Crazily enough, casein was inventedway before the 1930s – apparently they’ve discovered that many churches from the 14th and 15th centuries were painted with casein-based paints – the colors are still bright and unfaded even to this day! Well, apparently this milk casein stuff is great for paint. But how does that connect with milk fiber?
Apparently “milk casein” fiber was used in many clothing and household items in America and Europe during the 1930s and ’40s, says Joan Kiplinger of Fabrics.net. It was substitute for wool, which was needed by men on the front lines. However, it fell out of use after WWII ended and newer, cheaper synthetics such as nylon grew in popularity. The fiber was blended with other natural fibers and known under the brand names of Aralac, Lanatil and Merinova, for those of you checking your vintage clothing labels. While these brands’ fabrics were very similar to wool and could be dyed by the same processes, apparently there were some flaws with the milk casein fiber – namely, that it was not as strong and firm, nor as elastic as wool, and the fibers mildewed easily when they got damp.
Production Process of Milk Fiber:
Milk protein fiber production line application processing system can not do without the cooperation of the link. Shanghai is home on R & D Technology Co., Ltd. milk silk protein fibers, also engaged in spinning, dyeing and finishing of technical research, raw material quality, technology is complete, customers can better support the promotion of milk fiber.
Milk protein fiber can be used, in theory, cationic dyes, direct dyes, acid dyes, reactive dyes, neutral dyes, generally more than the actual cationic dye and reactive dye used is suitable for pure milk protein fiber and its products, such as staple fiber, yarn line, knitted fabrics, woven fabrics and garments. Period in order to milk protein fiber textiles as an example of pure cationic dyes and reactive dyes on the usage described as follows.
 |
| Flow chart of milk fiber |
Cationic dyes and finishing the first treatment process, due to temperature and moisture absorption of the products are strong, so do not need special treatment. With 60 ?water, liquid running back 10s, and then the second can of cold wash. In the special white process, the use of prescription and bleaching conditions were as follows: 5% sodium hydrosulfite (95 ?with warm water even after accession); 5% of the standard soap powder (use warm water even after the accession), not alkaline , does not contain brighteners; bath ratio 1:20 ~ 30; temperature of 95 ~ 98 ? time is about 15s ~ 30s, but also according to liquor ratio, equipment and raw materials of different thickness to adjust. Note that, if so special white, raw materials without cooling; If the training is finished, then white, must be 2% to 3% of the HAC, 60 ?water running 5s ~ 10s, cold washed twice, and then softening. Prescription and use of the whitening process conditions: 1.6% cationic brighteners (Dilute with warm water even after accession); 3% HAC (Dilute with warm water even after accession); temperature of 95 ~ 98 ? time of 15s ~ 20s ; bath ratio 1:25 ~ 30. In the dyeing process, the basic cationic dye with the general approach, but not 1227, and NaAc. To liquor ratio 1:25 to 30, for example, dyeing conditions to control the following table. Cleaning, light to be 1 or 2 times the cold wash, cold wash in the dark to be 1 or 2 times and then wash with hot water, 70 ?10s, and finally cold wash 1 or 2 times. In the post-treatment processes, the use of softener 5% to 8%; temperature 45 ~ 50 ? time of 20s or so; bath ratio 1:20 ~ 25.
According to different requirements of customers can choose different softeners, such as the fabric soft, smooth, elastic anti-wrinkle, anti-contamination, etc. when requested, by the production units to decide. In the dehydration process, in order to reduce the discount video, dehydration, slower, time is shorter, usually 1 minute each time, while patients have to row together, try not to let cloth folded. In the drying process, the use of the cage drying temperature of 80 ? 5 ? time is 20s ~ 30s, speed too quickly, after drying grounds lit 12 to 24 hours after the stereotypes. Using rotary drying temperature of 90 ? 5 ? fast speed, the disadvantage is the easy bit like a very light, must be strictly controlled temperature.
In the setting process, the general shape of water rolling open sites, the effect is better than the cylindrical shape. Process parameters are 150 ? 5% overfeed of 10%, the line speed 15m / s, the pressure head of about 4kg. Reactive dyeing of basic aspects of pre-treatment with the former, but if the dye houses using recycled water, pH value may be unstable or reactive groups dealing with different materials, can be the first treatment bath by adding 1% of the HAC, it will give the pH value of the cloth evenly from the inside out, but also conducive to color dyes.
Proven, low temperature dyeing cotton used reactive dyes more suitable, light-colored soda instead of baking soda can be used as dyeing auxiliaries, the amount can be as long as required to achieve the color, the dark can be used for dyeing auxiliary sodium sulfate and soda ash , the amount of cotton fiber dyed with similar.
Uses of Milk or Casein Fiber:
Because of the healthy & bacteriostatic nature of milk Fiber, it is being considered as a perfect material for manufacturing of underwear. As discussed above, milk casein proteins are considered as a main ingredient of milk protein Fiber, which can lubricate the skin. The milk protein contains the natural humectant factor which can help to maintain the skin moisture, to reduce the wrinkles & to smoothen the skin - which may help to realize the people of taking milk bath.
The major usages of milk Fiber are as given below:
- T-Shirts
- Underwear
- Sportswear
- Ladies outerwear
- Sweaters
15 November 2012
Dyeing of Glass Fiber
Glass Fiber:
Dyeing of Glass Fiber:
Dyeing of glass fiber filaments, fabrics or fabric is not so easy. In this case, it must be taken into consideration that, under normal circumstances, there is no affinity between glass fiber and dye and that no penetration of the dye into the glass fiber is possible, only surface dyeing or coloration is possible.
The following overview includes patented processes of glass fiber dyeing or coloration which must be regarded as being legally protected:
1. Fused mass coloration or dyeing: Using coloured metal oxides yielding weak dyes only as the colour intensity inevitably decreases with the cross section of the filament.
2. Dyeing of activated surfaces of glass fiber: Predominantly older processes of relatively little practical importance and usually yielding weak coloration, deficient in crocking fastness and, almost without exception, having a tendency to damage the fibers surface.
3. Direct dyeing methods of glass fiber: Without pre-treatment, using conventional dyeing techniques and, in this case, yielding surface coloration or dyeing which is barely acceptable. Methods involving the deposition of water-insoluble dyes are exceptions to this but usually only weak coloration can be achieved, e.g., when using sulphur or vat dyes.
4. Pre-mordanting dyeing methods:
Glass fiber
is a material consisting of numerous extremely fine fibers of glass.
Fiberglass is a strong and lightweight reinforcement used in composites,
communication, data transfer, or decorative purpose. Glass fibers able
to transfer light, ray and radiation inside its subtle hole. Although
strength properties are somewhat lower than carbon fiber and it is less
stiff, the material is typically far less brittle, and the raw materials
are much less expensive.
 |
| Glass fiber fabric |
Dyeing of glass fiber filaments, fabrics or fabric is not so easy. In this case, it must be taken into consideration that, under normal circumstances, there is no affinity between glass fiber and dye and that no penetration of the dye into the glass fiber is possible, only surface dyeing or coloration is possible.
The following overview includes patented processes of glass fiber dyeing or coloration which must be regarded as being legally protected:
- Fused mass coloration or dyeing
- Dyeing of activated surfaces of glass fibre
- Direct dyeing methods of glass fibre
- Pre-mordanting dyeing methods
- Bonding-agent dyeing methods
1. Fused mass coloration or dyeing: Using coloured metal oxides yielding weak dyes only as the colour intensity inevitably decreases with the cross section of the filament.
2. Dyeing of activated surfaces of glass fiber: Predominantly older processes of relatively little practical importance and usually yielding weak coloration, deficient in crocking fastness and, almost without exception, having a tendency to damage the fibers surface.
3. Direct dyeing methods of glass fiber: Without pre-treatment, using conventional dyeing techniques and, in this case, yielding surface coloration or dyeing which is barely acceptable. Methods involving the deposition of water-insoluble dyes are exceptions to this but usually only weak coloration can be achieved, e.g., when using sulphur or vat dyes.
4. Pre-mordanting dyeing methods:
a) metal-salt process gives strong colours in some cases but almost always with insufficient crocking fastness,
b) cation active process gives very strong colorations which, with the
right choice of dye, can have good fastness properties against water and
light but only moderate crocking fastness.
5. Bonding-agent dyeing methods: Coating with dyeable or dyed films:
5. Bonding-agent dyeing methods: Coating with dyeable or dyed films:
a) Pigment dyeing methods are the most
elegant and simplest to use. Pale to medium shades are possible with
maximum light, water and crocking fastness (with the right choice of
dye) while the properties of the dark colours (marine and black) are
frequently much worse. The principle consists of fixing the pigment
using synthetic resins.
b) Other bonding-agent dyeing methods
are to some extent still very inconvenient and unsatisfactory
(especially with regard to crocking fastness). Exception: Õ Corona
discharge process with good overall fastness but crocking fastness and
grease resistance are not completely satisfactory. No dark full shades
obtainable.
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26 October 2012
Characteristics, Manufacturing, End Uses of Rayon
Rayon
is the oldest commercial manmade fiber. It is a manufactured fiber
composed of regenerated cellulose, as well as manufactured fibers
composed of regenerated cellulose in which substituents have replaced
not more than 15% of the hydrogens of the hydroxyl groups. Rayon fibers
include yarns and fibers made by the viscose process, the cuprammonium
process, and the now obsolete nitrocellulose and saponified acetate
processes. Generally, in the manufacture of rayon, cellulose derived
from wood pulp, cotton linters, or other vegetable matter is dissolved
into a viscose spinning solution. The solution is extruded into an
acid-salt coagulating bath and drawn into continuous filaments. Groups
of these filaments may be made in the form of yarns or cut into staple.
Characteristics of Rayon Fiber :
Characteristics of Rayon Fiber :
- Highly absorbent
- Soft and comfortable
- Easy to dye
- Drapes well
Types of Rayons
Rayon fibers are engineered to possess a range of properties to meet the demands for a wide variety of end uses. Types of rayon fiber are given below:
- High wet modulus rayon
- Polynosic rayon
- Specialty rayons
- Super absorbent rayons
- Tencel rayon
- Lyocell
While there are many variations in the manufacturing process that exploit the versatility of the fiber, the following is a description of the procedure that is used in making regular or viscose rayon.
Regardless of whether wood pulp or cotton linters are used, the basic raw material for making rayon must be processed in order to extract and purify the cellulose. The resulting sheets of white, purified cellulose are then treated to form regenerated cellulose filaments. In turn, these filaments are spun into yarns and eventually made into the desired fabric.
The process of manufacturing viscose rayon consists of the following steps mentioned, in the order that they are carried out: (1) Steeping, (2) Pressing, (3) Shredding, (4) Aging, (5) Xanthation, (6) Dissolving, (7)Ripening, (8) Filtering, (9) Degassing, (10) Spinning, (11) Drawing, (12) Washing, (13) Cutting. The various steps involved in the process of manufacturing viscose are explained below.
 |
| Figure : Process of manufacture of viscose rayon fiber |
1. Steeping:
Cellulose
pulp is immersed in 17-20% aqueous sodium hydroxide (NaOH) at a
temperature in the range of 18 to 25°C in order to swell the cellulose
fibers and to convert cellulose to alkali cellulose.
(C6H10O5)n + nNaOH ---> (C6H9O4ONa)n + nH2O
(C6H10O5)n + nNaOH ---> (C6H9O4ONa)n + nH2O
2. Pressing:
The
swollen alkali cellulose mass is pressed to a wet weight equivalent of
2.5 to 3.0 times the original pulp weight to obtain an accurate ratio of
alkali to cellulose.
3. Shredding:
The
pressed alkali cellulose is shredded mechanically to yield finely
divided, fluffy particles called "crumbs". This step provides increased
surface area of the alkali cellulose, thereby increasing its ability to
react in the steps that follow.
4. Aging:
The
alkali cellulose is aged under controlled conditions of time C) in
order to depolymerize the°and temperature (between 18 and 30 cellulose
to the desired degree of polymerization. In this step the average
molecular weight of the original pulp is reduced by a factor of two to
three. Reduction of the cellulose is done to get a viscose solution of
right viscosity and cellulose concentration.
5. Xanthation:
In
this step the aged alkali cellulose crumbs are placed in vats and are
allowed to react with carbon disulphide under controlled temperature (20
to 30°C) to form cellulose xanthate.
(C6H9O4ONa)n + nCS2 ----> (C6H9O4O-SC-SNa)n
Side reactions that occur along with the conversion of alkali cellulose to cellulose xanthate are responsible for the orange color of the xanthate crumb and also the resulting viscose solution. The orange cellulose xanthate crumb is dissolved in dilute sodium hydroxide at 15 to 20 °C under high-shear mixing conditions to obtain a viscous orange colored solution called "viscose", which is the basis for the manufacturing process. The viscose solution is then filtered (to get out the insoluble fiber material) and is deaerated.
(C6H9O4ONa)n + nCS2 ----> (C6H9O4O-SC-SNa)n
Side reactions that occur along with the conversion of alkali cellulose to cellulose xanthate are responsible for the orange color of the xanthate crumb and also the resulting viscose solution. The orange cellulose xanthate crumb is dissolved in dilute sodium hydroxide at 15 to 20 °C under high-shear mixing conditions to obtain a viscous orange colored solution called "viscose", which is the basis for the manufacturing process. The viscose solution is then filtered (to get out the insoluble fiber material) and is deaerated.
6. Dissolving:
The
yellow crumb is dissolved in aqueous caustic solution. The large
xanthate substituents on the cellulose force the chains apart, reducing
the interchain hydrogen bonds and allowing water molecules to solvate
and separate the chains, leading to solution of the otherwise insoluble
cellulose. Because of the blocks of un-xanthated cellulose in the
crystalline regions, the yellow crumb is not completely soluble at this
stage. Because the cellulose xanthate solution (or more accurately,
suspension) has a very high viscosity, it has been termed "viscose".
7. Ripening:
The
viscose is allowed to stand for a period of time to "ripen". Two
important process occur during ripening: Redistribution and loss of
xanthate groups. The reversible xanthation reaction allows some of the
xanthate groups to revert to cellulosic hydroxyls and free CS2. This
free CS2 can then escape or react with other hydroxyl on other portions
of the cellulose chain. In this way, the ordered, or crystalline,
regions are gradually broken down and more complete solution is
achieved. The CS2 that is lost reduces the solubility of the cellulose
and facilitates regeneration of the cellulose after it is formed into a
filament.
(C6H9O4O-SC-SNa)n + nH2O ---> (C6H10O5)n + nCS2 + nNaOH
(C6H9O4O-SC-SNa)n + nH2O ---> (C6H10O5)n + nCS2 + nNaOH
8. Filtering:
The
viscose is filtered to remove undissolved materials that might disrupt
the spinning process or cause defects in the rayon filament.
9. Degassing:
Bubbles
of air entrapped in the viscose must be removed prior to extrusion or
they would cause voids, or weak spots, in the fine rayon filaments.
10. Spinning - (Wet Spinning):
Production
of Viscose Rayon Filament: The viscose solution is metered through a
spinnerette into a spin bath containing sulphuric acid (necessary to
acidify the sodium cellulose xanthate), sodium sulphate (necessary to
impart a high salt content to the bath which is useful in rapid
coagulation of viscose), and zinc sulphate (exchange with sodium
xanthate to form zinc xanthate, to cross link the cellulose molecules).
Once the cellulose xanthate is neutralized and acidified, rapid
coagulation of the rayon filaments occurs which is followed by
simultaneous stretching and decomposition of cellulose xanthate to
regenerated cellulose. Stretching and decomposition are vital for
getting the desired tenacity and other properties of rayon. Slow
regeneration of cellulose and stretching of rayon will lead to greater
areas of crystallinity within the fiber, as is done with high-tenacity
rayons.
The dilute sulphuric acid decomposes the xanthate and regenerates cellulose by the process of wet spinning. The outer portion of the xanthate is decomposed in the acid bath, forming a cellulose skin on the fiber. Sodium and zinc sulphates control the rate of decomposition (of cellulose xanthate to cellulose) and fiber formation.
(C6H9O4O-SC-SNa)n + (n/2)H2SO4 --> (C6H10O5)n + nCS2 + (n/2)Na2SO4
Elongation-at-break is seen to decrease with an increase in the degree of crystallinity and orientation of rayon.
The dilute sulphuric acid decomposes the xanthate and regenerates cellulose by the process of wet spinning. The outer portion of the xanthate is decomposed in the acid bath, forming a cellulose skin on the fiber. Sodium and zinc sulphates control the rate of decomposition (of cellulose xanthate to cellulose) and fiber formation.
(C6H9O4O-SC-SNa)n + (n/2)H2SO4 --> (C6H10O5)n + nCS2 + (n/2)Na2SO4
Elongation-at-break is seen to decrease with an increase in the degree of crystallinity and orientation of rayon.
11. Drawing:
The
rayon filaments are stretched while the cellulose chains are still
relatively mobile. This causes the chains to stretch out and orient
along the fiber axis. As the chains become more parallel, interchain
hydrogen bonds form, giving the filaments the properties necessary for
use as textile fibers.
12. Washing:
The
freshly regenerated rayon contains many salts and other water soluble
impurities which need to be removed. Several different washing
techniques may be used.
13. Cutting:
If
the rayon is to be used as staple (i.e., discreet lengths of fiber),
the group of filaments (termed "tow") is passed through a rotary cutter
to provide a fiber which can be processed in much the same way as cotton
.
Major End Uses of Rayon Fiber :
1. Apparel: Accessories, blouses, dresses, jackets, lingerie, linings, millinery, slacks, sportshirts, sportswear, suits, ties, work clothes
2. Home Furnishings: Bedspreads, blankets, curtains, draperies, sheets, slipcovers, tablecloths, upholstery
3. Industrial Uses: Industrial products, medical surgical products, nonwoven products, tire cord
13 October 2012
Carbon Fiber
Carbon Fiber:
Carbon
fiber is a high-tensile fiber or whisker made by heating rayon or
polyacrylonitrile fibers or petroleum residues to appropriate
temperatures. Fibers may be 7 to 8 microns in diameter and are more that
90% carbonized.
This fibers are the stiffest and strongest reinforcing fibers for polymer composites, the most used after glass fibers. Made of pure carbon in form of graphite, they have low density and a negative coefficient of longitudinal thermal expansion.
Carbon fibers are very expensive and can give galvanic corrosion in contact with metals. They are generally used together with epoxy, where high strength and stiffness are required, i.e. race cars, automotive and space applications, sport equipment.
 |
| Carbon fiber Weave |
This fibers are the stiffest and strongest reinforcing fibers for polymer composites, the most used after glass fibers. Made of pure carbon in form of graphite, they have low density and a negative coefficient of longitudinal thermal expansion.
Carbon fibers are very expensive and can give galvanic corrosion in contact with metals. They are generally used together with epoxy, where high strength and stiffness are required, i.e. race cars, automotive and space applications, sport equipment.
Depending on the orientation of the fiber, the carbon fiber composite can be stronger in a certain direction or equally strong in all directions. A small piece can withstand an impact of many tons and still deform minimally. The complex interwoven nature of the fiber makes it very difficult to break.
Characteristics/Properties of Carbon Fibers
Based on modulus, strength, and final heat treatment temperature, carbon fibers can be classified into the following categories:
- Physical strength, specific toughness, light weight.
- Good vibration damping, strength, and toughness.
- High dimensional stability, low coefficient of thermal expansion, and low abrasion.
- Electrical conductivity.
- Biological inertness and x-ray permeability.
- Fatigue resistance, self-lubrication, high damping.
- Electromagnetic properties.
- Chemical inertness, high corrosion resistance.
Based on modulus, strength, and final heat treatment temperature, carbon fibers can be classified into the following categories:
- Based on carbon fiber properties,
- Based on precursor fiber materials,
- Based on final heat treatment temperature,
- Ultra-high-modulus, type UHM (modulus >450Gpa)
- High-modulus, type HM (modulus between 350-450Gpa)
- Intermediate-modulus, type IM (modulus between 200-350Gpa)
- Low modulus and high-tensile, type HT (modulus < 100Gpa, tensile strength > 3.0Gpa)
- Super high-tensile, type SHT (tensile strength > 4.5Gpa)
- PAN-based carbon fibers
- Pitch-based carbon fibers
- Mesophase pitch-based carbon fibers
- Isotropic pitch-based carbon fibers
- Rayon-based carbon fibers
- Gas-phase-grown carbon fibers
- High-heat-treatment carbon fibers (HTT), where final heat treatment temperature should be above 2000°C and can be associated with high-modulus type fiber.
- Intermediate-heat-treatment carbon fibers (IHT), where final heat treatment temperature should be around or above 1500°C and can be associated with high-strength type fiber.
- Low-heat-treatment carbon fibers, where final heat treatment temperatures not greater than 1000°C. These are low modulus and low strength materials.
Application/Uses of Carbon Fiber
The two main applications of carbon fibers are in specialized technology, which includes aerospace and nuclear engineering, and in general engineering and transportation, which includes engineering components such as bearings, gears, cams, fan blades and automobile bodies. Recently, some new applications of carbon fibers have been found. Such as rehabilitation of a bridge in building and construction industry. Others include: decoration in automotive, marine, general aviation interiors, general entertainment and musical instruments and after-market transportation products. Conductivity in electronics technology provides additional new application.
The two main applications of carbon fibers are in specialized technology, which includes aerospace and nuclear engineering, and in general engineering and transportation, which includes engineering components such as bearings, gears, cams, fan blades and automobile bodies. Recently, some new applications of carbon fibers have been found. Such as rehabilitation of a bridge in building and construction industry. Others include: decoration in automotive, marine, general aviation interiors, general entertainment and musical instruments and after-market transportation products. Conductivity in electronics technology provides additional new application.
Application Carbon Fiber are given as Shortly:
- Aerospace, road and marine transport, sporting goods.
- Missiles, aircraft brakes, aerospace antenna and support structure, large telescopes, optical benches, waveguides for stable high-frequency (GHz) precision measurement frames.
- Audio equipment, loudspeakers for Hi-fi equipment, pickup arms, robot arms.
- Automobile hoods, novel tooling, casings and bases for electronic equipments, EMI and RF shielding, brushes.
- Medical applications in prostheses, surgery and x-ray equipment, implants, tendon/ligament repair.
- Textile machinery, genera engineering.
- Chemical industry; nuclear field; valves, seals, and pump components in process plants.
- Large generator retaining rings, radiological equipment.
Carbon fibre can be found in a wide range of performance vehicles including sports cars, superbikes, pedal bikes (where they are used to make frames), powerboats and it is often used in the tuning and customising industry where attractive woven panels are left unpainted to 'show off' the material.
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13 September 2012
Introduction of Glass Fiber
Glass fiber also called fiberglass. It is material made from extremely fine fibers of
glass Fiberglass is a lightweight, extremely strong, and robust
material. Although strength properties are somewhat lower than carbon
fiber and it is less stiff, the material is typically far less brittle,
and the raw materials are much less expensive. Its bulk strength and
weight properties are also very favorable when compared to metals, and
it can be easily formed using molding processes. Glass is the oldest,
and most familiar, performance fiber. Fibers have been manufactured from
glass since the 1930s.
Types of Glass Fiber
As to the raw material glass used to make glass fibres or nonwovens of glass fibres, the following classification is known:
1. A-glass: With regard to its composition, it is close to window glass. In the Federal Republic of Germany it is mainly used in the manufacture of process equipment.
2. C-glass: This kind of glass shows better resistance to chemical impact.
3. E-glass: This kind of glass combines the characteristics of C-glass with very good insulation to electricity.
4. AE-glass: Alkali resistant glass.
Generally, glass consists of quartz sand, soda, sodium sulphate, potash, feldspar and a number of refining and dying additives. The characteristics, with them the classification of the glass fibres to be made, are defined by the combination of raw materials and their proportions. Textile glass fibres mostly show a circular
Properties of Glass Fiber
Glass fibers are useful because of their high ratio of surface area to weight. However, the increased surface area makes them much more susceptible to chemical attack. By trapping air within them, blocks of glass fiber make good thermal insulation, with a thermal conductivity of the order of 0.05 W/(mK).
The strength of glass is usually tested and reported for "virgin" or pristine fibers those which have just been manufactured. The freshest, thinnest fibers are the strongest because the thinner fibers are more ductile. The more the surface is scratched, the less the resulting tenacity. Because glass has an amorphous structure, its properties are the same along the fiber and across the fiber. Humidity is an important factor in the tensile strength. Moisture is easily adsorbed, and can worsen microscopic cracks and surface defects, and lessen tenacity.
In contrast to carbon fiber, glass can undergo more elongation before it breaks. There is a correlation between bending diameter of the filament and the filament diameter. The viscosity of the molten glass is very important for manufacturing success. During drawing (pulling of the glass to reduce fiber circumference), the viscosity should be relatively low. If it is too high, the fiber will break during drawing. However, if it is too low, the glass will form droplets rather than drawing out into fiber.
Glass Fiber Manufacturing Processes
After the initial process of melting glass and passing it through spinnerets, continuous filaments or staple fibers of glass are manufactured by two different methods.
Continuous Filament Process
In this process, continuous filaments of indefinite length is produced. The molten glass passes through spinnerets having hundreds of small openings. These strands of multiple filaments are carried to winder revolving at very high speed of more than 2 miles per km. This process draws out the fibers in parallel filaments of the diameter of the openings. A sizing or a binder is applied to facilitate the twisting and winding process and to prevent breakage during yarn formation. After winding, filaments are further twisted and plied to make yarns by methods similar to those for making other continuous filament yarns. The sizing is removed through volatizing in an oven. These yarns are used for making such items as curtains and drapes.
Staple Fiber Process
Fibers with long-staple qualities are manufactured through staple fiber process. There are many methods for producing such fibers.
In one of such methods, the molten glass flows through the small holes of bushing, where jets of compressed air shake the thin streams of molten glass into fine fibers. These fibers vary in length ranging from 8 to 15 inches. The fibers fall through a spray of lubricant and a drying flame onto e revolving drum where they form into a thin web. These fibers in the form of web are gathered from the drum into a sliver. Yarn is then made from this sliver by similar methods that are adopted for making cotton or wool yarns. These yarns are used for fabrics for industrial purposes where insulation is required.
In yet another method, the ends of the glass rods are melted from which drops of glass fall away drawing off glass filaments after them onto a speedily revolving cylinder where they are wound parallel to each other. A web of sliver is formed if the cylinder moves sideways. Sometimes, the staple may be thrown off the cylinder onto a stationary sieve where it forms a sliver. In either conditions, the sliver is then converted into spun yarn.
The staple fiber, if subjected to oven, is compressed to the desired thickness and the binder which was earlier applied, is cured. This permanently binds the fibers.
Production:
The subsequent manufacture of glass fibres may be executed to the direct melting process. However, in most cases glass rods or balls are made first which then may undergo a variety of further processes.
Nozzle-Drawing:
As can be seen in Fig. 1-50, the glass fed in is melted in a heated melt tub at 1250–1400oC. Then, it emerges at the bottom of the melt tub from nozzle holes of 1–25 mm diameter and it is taken off and drawn. The filaments solidify and are finished and wound. One can find them in the shops as various kinds of “glass silk”. To make them into webs, the filaments are cut to length (mostly, between 6 and 25 mm).
Types of Glass Fiber
As to the raw material glass used to make glass fibres or nonwovens of glass fibres, the following classification is known:
1. A-glass: With regard to its composition, it is close to window glass. In the Federal Republic of Germany it is mainly used in the manufacture of process equipment.
2. C-glass: This kind of glass shows better resistance to chemical impact.
3. E-glass: This kind of glass combines the characteristics of C-glass with very good insulation to electricity.
4. AE-glass: Alkali resistant glass.
Generally, glass consists of quartz sand, soda, sodium sulphate, potash, feldspar and a number of refining and dying additives. The characteristics, with them the classification of the glass fibres to be made, are defined by the combination of raw materials and their proportions. Textile glass fibres mostly show a circular
Properties of Glass Fiber
Glass fibers are useful because of their high ratio of surface area to weight. However, the increased surface area makes them much more susceptible to chemical attack. By trapping air within them, blocks of glass fiber make good thermal insulation, with a thermal conductivity of the order of 0.05 W/(mK).
The strength of glass is usually tested and reported for "virgin" or pristine fibers those which have just been manufactured. The freshest, thinnest fibers are the strongest because the thinner fibers are more ductile. The more the surface is scratched, the less the resulting tenacity. Because glass has an amorphous structure, its properties are the same along the fiber and across the fiber. Humidity is an important factor in the tensile strength. Moisture is easily adsorbed, and can worsen microscopic cracks and surface defects, and lessen tenacity.
In contrast to carbon fiber, glass can undergo more elongation before it breaks. There is a correlation between bending diameter of the filament and the filament diameter. The viscosity of the molten glass is very important for manufacturing success. During drawing (pulling of the glass to reduce fiber circumference), the viscosity should be relatively low. If it is too high, the fiber will break during drawing. However, if it is too low, the glass will form droplets rather than drawing out into fiber.
Glass Fiber Manufacturing Processes
After the initial process of melting glass and passing it through spinnerets, continuous filaments or staple fibers of glass are manufactured by two different methods.
Continuous Filament Process
In this process, continuous filaments of indefinite length is produced. The molten glass passes through spinnerets having hundreds of small openings. These strands of multiple filaments are carried to winder revolving at very high speed of more than 2 miles per km. This process draws out the fibers in parallel filaments of the diameter of the openings. A sizing or a binder is applied to facilitate the twisting and winding process and to prevent breakage during yarn formation. After winding, filaments are further twisted and plied to make yarns by methods similar to those for making other continuous filament yarns. The sizing is removed through volatizing in an oven. These yarns are used for making such items as curtains and drapes.
Staple Fiber Process
Fibers with long-staple qualities are manufactured through staple fiber process. There are many methods for producing such fibers.
In one of such methods, the molten glass flows through the small holes of bushing, where jets of compressed air shake the thin streams of molten glass into fine fibers. These fibers vary in length ranging from 8 to 15 inches. The fibers fall through a spray of lubricant and a drying flame onto e revolving drum where they form into a thin web. These fibers in the form of web are gathered from the drum into a sliver. Yarn is then made from this sliver by similar methods that are adopted for making cotton or wool yarns. These yarns are used for fabrics for industrial purposes where insulation is required.
In yet another method, the ends of the glass rods are melted from which drops of glass fall away drawing off glass filaments after them onto a speedily revolving cylinder where they are wound parallel to each other. A web of sliver is formed if the cylinder moves sideways. Sometimes, the staple may be thrown off the cylinder onto a stationary sieve where it forms a sliver. In either conditions, the sliver is then converted into spun yarn.
The staple fiber, if subjected to oven, is compressed to the desired thickness and the binder which was earlier applied, is cured. This permanently binds the fibers.
Production:
The subsequent manufacture of glass fibres may be executed to the direct melting process. However, in most cases glass rods or balls are made first which then may undergo a variety of further processes.
Nozzle-Drawing:
As can be seen in Fig. 1-50, the glass fed in is melted in a heated melt tub at 1250–1400oC. Then, it emerges at the bottom of the melt tub from nozzle holes of 1–25 mm diameter and it is taken off and drawn. The filaments solidify and are finished and wound. One can find them in the shops as various kinds of “glass silk”. To make them into webs, the filaments are cut to length (mostly, between 6 and 25 mm).
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| Manufacture of glass melt |
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| Processes to make glass fibres |
Nozzle-Blowing:
The same as with nozzle-drawing, glass balls are melted in the tub. The melt emerging from the nozzle holes is then taken by pressed air, which draws the liquid glass so as to make fibres of 6–10 um diameter. A fluttering effect is caused by the flow of pressed air, which results in fibres of lengths from 50 to 300 mm. A lubricant is put on and the fibres are laid down on a sieve drum which sucks them in. The dry web received is held together by the long fibres, the short ones lying in between them as a filling material. Then, the slivers of glass fibre material are cut.
Rod-Drawing:
By means of a burner, bundles of glass rods are melted at their bottom ends. This results in drops which, as they fall down, draw filaments after them. The filaments are taken by a rotating drum, a squeegee laying them down onto a perforated belt. Thus, a dry web is received which can be wound as glass fibre slivers. – Machine performance being limited by the number of glass rods fed in, the rotating drum may be combined with nozzle-drawing, which results in drum-drawing. This multiplies machine performance. The dry web is again laid down onto a perforated belt and solidified or, after winding it so as to receive slivers, cut for further processing on machines producing wetlaid nonwovens. Using and processing glass fibres is not without any problems. For example, fine pieces of broken fibres may disturb if the work place is not well prepared for the purpose. Using the nonwovens to manufacture glass-fibre reinforced plastics, it is important the surface of the plastic material is fully even. Ends of fibre looking out may be pulled out or loosened by outward stress (temperature, gases, liquids), which may influence material characteristics. In some cases, it is
advisable to cover up such layers of glass fibre with suitable chemical fibres.
Uses of Glass Fiber or Glass Yarn
Glass fiber is manufactured in a wide range of fine diameters. Some of them are so fine that they can be seen only through a microscope. This quality of fineness contributes greatly to the flexibility of glass fibers. Various manufacturers produce different types of glass fibers for different end uses. Glass fibers them are used for various purpose.
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The same as with nozzle-drawing, glass balls are melted in the tub. The melt emerging from the nozzle holes is then taken by pressed air, which draws the liquid glass so as to make fibres of 6–10 um diameter. A fluttering effect is caused by the flow of pressed air, which results in fibres of lengths from 50 to 300 mm. A lubricant is put on and the fibres are laid down on a sieve drum which sucks them in. The dry web received is held together by the long fibres, the short ones lying in between them as a filling material. Then, the slivers of glass fibre material are cut.
Rod-Drawing:
By means of a burner, bundles of glass rods are melted at their bottom ends. This results in drops which, as they fall down, draw filaments after them. The filaments are taken by a rotating drum, a squeegee laying them down onto a perforated belt. Thus, a dry web is received which can be wound as glass fibre slivers. – Machine performance being limited by the number of glass rods fed in, the rotating drum may be combined with nozzle-drawing, which results in drum-drawing. This multiplies machine performance. The dry web is again laid down onto a perforated belt and solidified or, after winding it so as to receive slivers, cut for further processing on machines producing wetlaid nonwovens. Using and processing glass fibres is not without any problems. For example, fine pieces of broken fibres may disturb if the work place is not well prepared for the purpose. Using the nonwovens to manufacture glass-fibre reinforced plastics, it is important the surface of the plastic material is fully even. Ends of fibre looking out may be pulled out or loosened by outward stress (temperature, gases, liquids), which may influence material characteristics. In some cases, it is
advisable to cover up such layers of glass fibre with suitable chemical fibres.
Uses of Glass Fiber or Glass Yarn
Glass fiber is manufactured in a wide range of fine diameters. Some of them are so fine that they can be seen only through a microscope. This quality of fineness contributes greatly to the flexibility of glass fibers. Various manufacturers produce different types of glass fibers for different end uses. Glass fibers them are used for various purpose.
- For making home furnishings fabrics;
- For making apparels and garments; and
- For the purpose tires and reinforced plastics.
- Filament windings around rocket cases;
- Nose cones;
- Exhaust nozzles; and
- Heat shields for aeronautical equipment
- Boat hulls and seats;
- Fishing rods; and
- Wall paneling
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29 July 2012
Properties of Rayon
Rayon Fiber
Rayon is a manufactured fiber composed of regenerated cellulose, as well as manufactured fibers composed of regenerated cellulose in which substituents have replaced not more than 15% of the hydrogens of the hydroxyl groups.
Rayon is a manufactured fiber composed of regenerated cellulose, as well as manufactured fibers composed of regenerated cellulose in which substituents have replaced not more than 15% of the hydrogens of the hydroxyl groups.
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| Rayon fiber |
Physical Properties of Viscose Rayon
Moisture Absorption
It absorbs more moisture than cotton. Moisture Content of Coton is 6% at 70 deg F and 65% RH, and for Viscose Rayon it is 13% under the same conditions.
Tensile Strength
The Tensile Strength of the fibre is less when the fibre is wet than when dry. It is 1.5-2.4 gpd in the dry state and 0.7-1.2 gpd in the wet state. For high tenacity variety the values are 3-4.6 gpd and 1.9 to 3.0 gpd.
Elasticity
The elasticity of Viscose Rayon is less than 2-3%. This is very important in handling viscose yarns during weaving, stentering etc when sudden tensions are applied.
Elongation at Break
Ordinary Viscose rayon has 15-30% elongation at break, whule high tenacity rayon has only 9-17% elongation at break.
Density
The density of Viscose rayon is 1.53 g/cc. Rayon filaments are available in three densities: 1.5, 3.0 and 4.5
Action of Heat and Light
At 300 deg F or more, VR loses its strength and begins to decompose at 350-400 deg F. Prolonged exposure to sunlight also weakens the fibre due to moisture and ultraviolet light of the sunlight.
Chemical Properties of Viscose Rayon
Viscose rayon consists of cellulose of lower DP than cotton cellulose. Also amorphous region of Viscose rayon is present to a greater extent, therefore, Viscose rayon reacts faster than cotton with chemicals. Acids like H2SO4 HCL breaks the cellulose to hydrocellulose. Oxidising agents like Na(OCl)2, Bleaching powder, K2Cr2O7, KMnO4- form oxycellulose. Cold acid solutions for a short time do not attack viscose rayon.
It absorbs more moisture than cotton. Moisture Content of Coton is 6% at 70 deg F and 65% RH, and for Viscose Rayon it is 13% under the same conditions.
Tensile Strength
The Tensile Strength of the fibre is less when the fibre is wet than when dry. It is 1.5-2.4 gpd in the dry state and 0.7-1.2 gpd in the wet state. For high tenacity variety the values are 3-4.6 gpd and 1.9 to 3.0 gpd.
Elasticity
The elasticity of Viscose Rayon is less than 2-3%. This is very important in handling viscose yarns during weaving, stentering etc when sudden tensions are applied.
Elongation at Break
Ordinary Viscose rayon has 15-30% elongation at break, whule high tenacity rayon has only 9-17% elongation at break.
Density
The density of Viscose rayon is 1.53 g/cc. Rayon filaments are available in three densities: 1.5, 3.0 and 4.5
Action of Heat and Light
At 300 deg F or more, VR loses its strength and begins to decompose at 350-400 deg F. Prolonged exposure to sunlight also weakens the fibre due to moisture and ultraviolet light of the sunlight.
Chemical Properties of Viscose Rayon
Viscose rayon consists of cellulose of lower DP than cotton cellulose. Also amorphous region of Viscose rayon is present to a greater extent, therefore, Viscose rayon reacts faster than cotton with chemicals. Acids like H2SO4 HCL breaks the cellulose to hydrocellulose. Oxidising agents like Na(OCl)2, Bleaching powder, K2Cr2O7, KMnO4- form oxycellulose. Cold acid solutions for a short time do not attack viscose rayon.
Action of Acids:
The resistance of regenerated cellulose rayon’s to acids is generally less than that of cotton to the same concentrations of the same acids. Therefore , acid treatments must not be too drastic with respect to concentration ,temperature and time .Organic acids can be safely used in 1 to 2 percent concentration without injury to the fiber. Inorganic acids such as hydrochloric & nitric can be used in surprisingly strong concentrations provided the temperatures are not too high and the treatment is brief. Oxalic acid for removal of iron stains is not recommended except at temperatures lower than 150°F.At high temperatures and concentrations all acid will destroy or carbonize regenerated rayon’s. No harmful action will result if applied at .5 to 3 percent solution at room temperature.
Action of Soaps:
Ordinary soaps in usual textile concentration have no direct effect on regenerated cellulose materials. Improper use of soap or use of poorly made soap results in rancidity and odor in rayon fabrics or yarns. When soaps alone is used ,there is a tendency for the ionized fatty acid from the soap to adhere tenaciously to the individual rayon filaments. During the drying filament of such materials and subsequent storage .The free fatty acid radical is very likely to turn rancid & to give the goods & objectionable odor. This phenomenon is specially Prevalent on oil-delustered rayons, because the fatty acid radical of the soap adheres Tenaciously to the minute oil globules in the structure of the yarn.If given time enough the fatty acid radical
Action of Dry Heat:
Most regenerated celluloses, under the influence of heat as well as light ,show rapid loss in strength, this change being accompanied by a increase in copper number and alkali solubility. In a study of effect of drying conditions of textile yearns, Wiegerink in 1940 showed that the quality index of cellulose fibers decreases either as the temperature is increased or as the moisture content of the surrounding atmosphere is increased .Both the breaking strength & fluidity of viscose rayon appear to be functions of the relative humidity to which the samples are exposed. Degradation of cellulose is lower in the absence of oxygen. Continued heating , however , in the absence of oxygen leads to deterioration of the cellulose but little is known about the course of the reactions. Short heating at high temperatures ,such as 140°c is less harmful than long heating at lower temperatures. A decrease of tenacity & eventually a yellow to brown discoloration occurs on aging.
Action of Solvents
Textile solvents can be used on Viscose rayon without any deteriorating effect. Viscose rayon dissolves in cuprammonium hydroxide solution.
Effect of Iron
Contact with iron in the form of ferrous hydroxide weakens viscose rayon yarns. Therefore staining, marking or touching of rayon to iron or iron surface should be avoided.
Action of Microorganisms
Microorganisms ( moulds, mildew, fungus, bacteria) affect the colour, strength, dyeing properties and lustre of rayon. Clean and dry viscose rayon is rarely attacked by moulds and mildew.
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9 May 2012
Glass Fiber Composites
Glass Fiber Composites
Introduction:
Today, almost any specialization for structural material can be met by combination of glass fiber
and plastic resin, which are characterized by many outstanding
properties. During 1942 glass fiber reinforced composites were first
used in structural aerospace parts. In the early 1960’s high strength
glass fibers, S-Glass were first used in joint work between Owens
corning textile product and the united states air force later in 1968
S-2 glass began evolving into a variety of commercial application. High
strength glass fiber combine high strength, high stability, transparency
and resilience at a very reasonable cost-weight performance. The
utilities of high strength glass fiber composites are compared by
physical, mechanical, electrical, thermal, acoustical, optical and
radiation properties.
The glass fiber
composites strength/weight ratios are higher than those of most other
materials and their impact resistance is phenomenal. Further they
possess good electrical properties, resistance to moisture and outdoor
weathering and resistance to heat and chemicals. These properties are
coupled with ease of fabrication.
Composites:
Composites are artificially produced multiphase materials having a desirable combination of the best properties of the constituent phases or more precisely these are the materials consist of fibers of high strength and modulus embedded in or bonded to a matrix with distinct interfaces between them.
Properties of Glass Fibers:
Glass fibers basically made by,
Composites:
Composites are artificially produced multiphase materials having a desirable combination of the best properties of the constituent phases or more precisely these are the materials consist of fibers of high strength and modulus embedded in or bonded to a matrix with distinct interfaces between them.
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- Incombustibility
- Corrosion resistance
- High strength at low densities
- Good thermal.
- Sound insulation
- Special electrical properties.
- Mixing silica sand, limestone, boric acid and other minor ingredients.
- The mixture is heated until it melts at about 1260OC/2300OF.
- Letting the molten glass flow through fine holes. (In a platinum plate)
- The glass strands are cooled, gathered and wound. (Protective coating may be added.)
- The fibers are drawn to increase the directional strength.
- The fibers are woven into various forms for use in composites.
Type:
- A Soda-lime glass.
- E Electrical type (Borosilicate)
- C Chemical resistant type
- AR Alkali resistant type
- S High performance application
- General purpose glass fiber
- Quartz fiber
- Protective fiber
- Hollow fiber
- Conducting/Semi-conducting
Properties
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E-glass
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AR-glass
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S-glass
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Tensile Strength (Gpa)
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3.5
|
3.5
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4.6
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Modulus (Gpa)
|
73.5
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175
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86.8
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Elongation (%)
|
4.8
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2
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5.4
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Density (g/cc)
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2.57
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2.68
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2.46
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Refractive Index
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1.547
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1.561
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-
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Coefficient of Thermal
Expansion (107/0c)
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50-52.0
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75.0
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23-27.0
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Dielectric Constant RT, 1010
Hz
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6.1-6.3
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-
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5.0-5.1
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Forms of the Glass Fiber Reinforcement:
Glass Fabric:
This form of glass fiber is particularly suitable for high strength, low weight laminates. Continuous filament glass is preferred in these applications on account of it’s greater strength and low bulk factor. The fabric woven from continuous filament yarn ranges in thickness from 0.002-0.02 inches. In general directional properties of laminates depend on the type of weave and cloth setting employed. (We’ll discuss this later). The example of fabric-reinforced plastic is aircraft radar. In this application, a material is required which will allow the radar rays to go without distortion from the rays sending equipment out of the target and then back to the radar receiving equipment on the plane. It must also stand the air pressure strain of a sonic or supersonic speed. Combination of glass fabric and low-pressure plastic resin provides an excellent answer to these requirements.
Combination of glass fabrics and fire-proofed polyester resin are also used for making high strength flat and shaped laminates for aircraft components such as a ducting, panels, nose, wings tips, rudder parts, covers, dash-boards, shelves, floors
This material is also used for hollow fishing rods, where unidirectional fabric lends itself to winding round a solid mandrel, for body armor and for the manufacture of large article such as boats by the low pressure technique and for many other products.
Molding Techniques:
Molding methods are almost legion. At present count more than 22 general molding methods is basic process categories are widely used. These includes
1.Hand and spray saturating and mixing.
2.Continuous impregnation, laminating.
3.Cure or flat or corrugated panels, solid rods, hollow bar stock.
4.Compression, transfer and injection molding.
5.Filament wrapping and winding.
6.Centrifugal and static casting.
7.Rotational molding.
8.Cold forming.
9.Combination of those above.
Effect of Different Weaves:
The plain weave fabric having square setting i.e. equal number per inch of ends in the warp as picks, is employed where uniformity in strength is desired. Another popular structure is 8-shaft satin weave, in which each weft yarn goes under one and over seven warp yarns. It is mostly used in heavier fabrics when lamination calls for high strength in all direction and where a smooth surface and decorative appearance are desired. Due to lower crimp or ‘weaving take up’ the strength of a satin weave fabric is comparatively greater then of a plain weave fabric.
When maximum strength in one direction is required at a maximum weight, a unidirectional weave is employed. In order to produce such a fabric, usually a large amount of relatively strong warp yarn and fewer weaker weft yarns are employed.
Non-woven materials from glass fibre are dominated because least labour intensive and most efficient to manufacture.
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| Different weaves of glass fiber |
Glass fibre composites making in roads many markets due to general properties of excellent molded surface finish almost unlimited size, lightness of weight, insulation against heat transfer and electricity and many other attributes. These will become evident in ensuring discussion, build around in nine major market for GFC which includes following:
1.Aircraft and Aerospace
2.Appliances and equipments
3.Constructions
4.Consumer goods
5.Corrosion resistant product
6.Electrical rods, tubes and components
7.Marin and Marin accessories
8.Land transportation
9.Miscellaneous (Protective gears, Farming, industrial tools, material handling).
Aircraft and Aerospace Market:
Stability is an important criterion for any material used. Light weight with the ability to withstand heavy loads and provide excellent resistance to bumps and impact. Aerospace and aircraft applications include overhead storage bins, aircraft toilets and helicopter rotor blades. Other benefits from using composites for these applications include cost performance, dimensional stability and corrosion resistance.
Entire external fuselages of smaller planes have been constructed using GFC, interior and commercial plane (Boeing 747) entire exterior of flight vehicle guided missile
S-glass, which is the more exotic of the current reinforced glass products, has a much higher strength and modulus than E-glass. It also has a high laminate strength-to-weight ratio, high strength retention at elevated temperatures and a high fatigue life. It is very often used for aircraft components such as flight deck armour, and helicopter armour, seats and floors. Apart from their high mechanical performance, S-glass composites are inherently non-conductive and offer low radar thermal profiles, thereby providing the military with the opportunity to see without being seen S-glass fibre has proved itself by performing superbly in hazardous environments. Its strength and reliability have encouraged various manufacturers to use the fibre in fabricating composite blades for different models of helicopter . A new dimension to the applications of glass fibres is the use of hollow S-glass in fibre reinforced composites. In general, the mechanical properties of hollow S-2 glass compare favorably with standard fibre glass composites and show significant weight savings of approximately 16-18%.
Reinforcements commonly used
- Preform Rovings
- Roving for weaving
- Woven Roving
- Plied yarns
Construction and Infrastructure:
Composites are ideal for use in the construction market because of their dimensional stability, high strength, reduced weight, impact resistance, low flammability, given an appropriate choice of resins and additives, low maintenance and design flexibility.
Use in both interior and exterior building components for residential, commercial industrial and farm construction, tub, and shower units. Corrugated translucent architectural paneling, solar heating elements. Industrial building sky light, yard swimming pool fences and bathroom fixtures. (Resistant to mechanical impact and billing water
Exterior:
For rebuilding or creating new infrastructures, composite materials bring a number of benefits to various applications, including high strength, reduced weight, corrosion resistance, lower maintenance, dimensional stability, low installation costs and design flexibility. In bridge construction, for instance, composites provide a high load capacity with low material weight. This low composite weight eliminates the costs of heavy equipment needed to build the bridge, which in turn reduces the installation time. Composites are also very durable; they won't corrode like steel or rot like wood, so maintenance and replacement costs are reduced.
Consumer Goods:
Properties –leisure, recreational, basic frames for furniture as well as finished items both traditional and modern, also includes divider screens, decorative and utilities trays, wall plaques, luggage. In sports equipments skis, patio furniture, swimming pool, plays ground equipments, portable tennis courts tennis racquets fishing rods vaulting polls snow mobiles garden tractors skate boards and surf boards.
Properties: controlled
flexibility, high mechanical strength, lightness of weight, easy
formability, durability, molded in colours excellent surface and
resistant to corrosion and wear.
Corrosion Resistant Products/Equipments:
Exhaustive analyses of mechanism of corrosion in fiberglass and their composite structure are available in literature. Engineers and Managers have realized that superior corrosion resistant properties exist in glass fibre composites as compared to traditional material. Composites are ideally suited for corrosive, hostile environments. Applications in this market include all types of pipes, oilfield pipes, fume handling ducts, underground petrol tanks, sucker rods, water, wastewater, drainage and irrigation piping (potable water, sewage, storm drains), cooling towers, component for water and sewage treatment facilities in textile processing, flood control and navigational waterway structures (dam gates, pipes, grating, weirs), energy production structures for oil and gas production (offshore platforms, grating, piping) .
Composites are ideal for use in the construction market because of their dimensional stability, high strength, reduced weight, impact resistance, low flammability, given an appropriate choice of resins and additives, low maintenance and design flexibility.
Use in both interior and exterior building components for residential, commercial industrial and farm construction, tub, and shower units. Corrugated translucent architectural paneling, solar heating elements. Industrial building sky light, yard swimming pool fences and bathroom fixtures. (Resistant to mechanical impact and billing water
Exterior:
- Composites for exterior design are present in columns, pediments, domes, cornices
- Composites are used for paneling, cladding and covering for protection and insulation panels, shingles, translucent flat or corrugated sheets (facing systems, decorative fascia)
- Fascia renovation using glass-cement composites contributes to improving the appearance of buildings, external insulation and coatings of facades where dimensional stability and prevention against cracking is required.
- Composites form work and moulds for concrete, easy to make and corrosion-resistant.
- Roofing applications include sealing and waterproofing .
- Technical glass fabrics are used in the industrial filtration of gases, vapours and smoke.
- Doors and windows.
- Blinds (against sun or for decoration)
- Aesthetic coverings for use on walls, partitions, ceilings, doors and furniture
- Glass-reinforced plaster in a wide variety of shapes: columns, ceilings, cornices etc.
- Decor and furnishings of reinforced plastics and glass-cement composites
- Gypsum boards and partitions
- Dry wall tapes
- Partitions of glass-cement composites
- Composite panels (double-sided insulated, phenolic resins treated)
- Sanitary-ware (baths, wash basins, showers, sinks, toilets)
- Flooring (flexible flooring, hard flooring
- Functional items (letter boxes, meter boxes)
- Decorative items..
For rebuilding or creating new infrastructures, composite materials bring a number of benefits to various applications, including high strength, reduced weight, corrosion resistance, lower maintenance, dimensional stability, low installation costs and design flexibility. In bridge construction, for instance, composites provide a high load capacity with low material weight. This low composite weight eliminates the costs of heavy equipment needed to build the bridge, which in turn reduces the installation time. Composites are also very durable; they won't corrode like steel or rot like wood, so maintenance and replacement costs are reduced.
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| Glass fiber used in Construction |
Properties –leisure, recreational, basic frames for furniture as well as finished items both traditional and modern, also includes divider screens, decorative and utilities trays, wall plaques, luggage. In sports equipments skis, patio furniture, swimming pool, plays ground equipments, portable tennis courts tennis racquets fishing rods vaulting polls snow mobiles garden tractors skate boards and surf boards.
 |
Corrosion Resistant Products/Equipments:
Exhaustive analyses of mechanism of corrosion in fiberglass and their composite structure are available in literature. Engineers and Managers have realized that superior corrosion resistant properties exist in glass fibre composites as compared to traditional material. Composites are ideally suited for corrosive, hostile environments. Applications in this market include all types of pipes, oilfield pipes, fume handling ducts, underground petrol tanks, sucker rods, water, wastewater, drainage and irrigation piping (potable water, sewage, storm drains), cooling towers, component for water and sewage treatment facilities in textile processing, flood control and navigational waterway structures (dam gates, pipes, grating, weirs), energy production structures for oil and gas production (offshore platforms, grating, piping) .
 |
| Corrosion resistant products |
- Chopped Strand Mat
- Roving
- Continuous filament mats
- Woven Roving
- Yarns
- Glass mats
Substantial incursion of glass fibre composites into field requiring desirable properties for electrical and electronics applications. Mechanical strength and temperature stability were the factors, which favored the use of glass filament technical fabrics in industry as an insulator for electrical conductors. In association with lacquers and coatings, it is used for covering wires and cables. Weather stability, high dielectric strength, high arc resistance and good mechanical toughness were rapid once. These materials were proven in critical areas. They are used in distribution-pole hardware, switchgear, and transformers, telephone equipments, PCB’s, computer parts.
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| Glass fiber in transformer |
- Continuous Filament Mat
- Roving for pultrusion
- Roving for weaving
- Yarns
- Plied yarns
- Technical fabrics
- Chopped Strands for thermoplastic reinforcement
Marine Products/Accessories:
Properties of fibre glass composites so favorable that approx. 70% of all out board pleasure boats is now constructed with it. The major benefit of using GFC’s in any boat construction are mouldability to almost any boat design or size, seamless construction, high strength and great durability, minimum maintenance, freedom from corrosion, rust, dry rot and water logging.
 |
| Glass fiber used in marine |
Reinforcements commonly used:
- Chopped Strand Mats
- Continuous filament mats
- Woven Roving
- Yarns and Glass mats
The first real success splash of glass fibre composites in automotive or land transportation field was the 1953 corvette, which had complete glass fibre body. At the most recent count, more than 154 different automotive applications in GFC existed. The prime contribution of GFC is weight saving and this factor alone will go a long way toward helping automakers satisfy future energy consumption requirements. This is energy effectiveness at it’s best.
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| Glass fiber used in car |
- Chopped Strands
- Chopped Strand Mat
- Continuous Filament Mat
- Yarns
- Rovings for thermoplastic reinforcement
- Woven Roving
- Chopped Strands for thermoplastic reinforcement
Glass fibre is also used successfully in railway fishplates. These are produced from a combination of woven fabric and unidirectional nonwoven E-glass reinforcement by using an epoxy resin matrix.
Miscellaneous/Specialty Products:
The tooling industries are largest single facet making up this final marketing category for GFC parts. A comprehensive list would include such highly serviceable and behind-the-scenes component as temporary or short run forming dies for plastic and metals, checking fixture, hydro forming shapes, hammer forms, stretch dies, foundry patters and many other creative and utilitarian elements.
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By using their light and image transmission characteristics, optical fibres are also employed in the manufacture of medical instruments such as the gastroscope, in traffic-control signals, in various control instrumentation, in sales-code reading devices and so on.
Other applications are: Screening and filtration. Glass reinforced mortar/cement.
Appliance and Equipment :
Properties - heat insulation, noise reduction, excellent molded surfaces, dimensional stability, high dielectric strength frames, bases and housing for composites, time-share terminal units, similar appliances.
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With this, I want to conclude that these glass fibre composites really taking away the ”market” from conventional materials like metals. With further new technological advancement in fibreglass and resins, their composites always have been able to satisfy the need of any engineering field. At last I want to say that these GFC’s are solution for growing building engineering avenues.
References:
- “Fibre science and technology” By V.I.Kostikov.
- “Fiberglass” By Mohr & Rowe.
- “Inorganic fibers”
- “Fibre reinforced composites” – A seminar report.
- “Composite material in Health care & wound Management” Technical Textiles International, July-Aug 2003
- New Fibers By Tatsuya Houngu & Glyn O. Phillips
- Wellington Sears Handbook of Industrial Textiles By S. Adanur
- Handbook of Technical Textiles By A.R. Horrocks & S.C. Anand
- Textile Progress.
- Construction World, Jan. 2005.
- Composite Technology, Aug. 2003.
- Composite Technology, June 2003.
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