The acrylic fibers include acrylic, modacrylic, and alternative vinyl fibers containing cyanide groups as side chains. Among the most important acrylic fibers, acrylonitrile is that the comonomer containing a cyanide group. Acrylic fibers are formed from copolymers containing larger than 85th acrylonitrile monomer units, whereas modacrylic fibers contain 35%-85% acrylonitrile units. In general, these fibers possess a heat bulky hand, smart resiliency and wrinkle resistance, and overall favorable aesthetic properties.
Acrylic fibers are formed from wet or dry spinning of copolymers. After texturizing, acrylic fibers have a light, bulky, wool-like hand and overall wool-like aesthetics. The fibers are resilient and possess glorious acid and daylight resistance. Acrylics have been used extensively in applications formerly reserved for wool or other certain fibers.
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Fig 1: Structure of Acrylic Fiber |
1. Structural Properties
Acrylic fibers are created of copolymers containing a minimum of 85th nitril units together with one or a lot of comonomers including methyl group methacrylate, vinyl acetate, or vinyl pyridine (Fig. 1) The copolymer is created through free radical emulsion polymerisation. after precipitation, the copolymer is dried and dissolved in an applicable organic solvent and wet or dry spun. The degree of polymerisation of the copolymers used for fiber formation varies from 150 to 200 units. Pure polyacrylonitrile can type satisfactory fibers. owing to the extensive tight packing of adjacent molecular chains and also the high crystallinity of the fiber, comonomers should be introduced to lower the regularity and crystallinity of the polymer chains to create the fiber a lot of dye in a position. extensive hydrogen bonding happens between
oc-hydrogens and also the electronegative nitrile groups on adjacent polymer chains, and powerful van der Waals interactions further contribute to the packing of the acrylic chains. The periodic comonomer units interfere with this packing and, therefore, decrease the general crystallinity of acrylic fibers. Acrylic fibers are sometimes smooth with round or dog-bone cross sections (Fig. 2).
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Fig 2: |
2. Physical Properties
Acrylic fibers are fibers of moderate strength and elongations at break. The tenacity of acrylic fibers varies from 2 to 4 g/d (18-36 g/tex). On wetting, the tenacity drops to 1.5-3 g/d (13-27 g/tex). The elongation at break varies from 200th to 500th for the various acrylic fibers. At 2 elongation, the recovery of the fiber is 99%; but at 5-hitter elongation, the recovery is just 50%-95%. The fiber is moderately stiff and has wonderful resiliency and recovery from bending deformation. The fibers have low specific gravities of 1.16-1.18 and low wet regains of 1.0%-2.5% under standard temperature and humidity conditions. The fiber is soluble in polar aprotic solvents like N, N-dimethylformamide. The fiber exhibits good heat and electrical insulation properties. Acrylic fibers do build up moderate static charge and soften at 190°-250°C.
3. Chemical Properties
Acrylic fibers exhibit good chemical resistance. The fibers are solely attacked by concentrated acids and are slowly attacked and hydrolyzed by weak bases. Acrylics are unaffected by oxidizing and reducing agents except for hypochlorite solutions at elevated temperatures. Acrylic fibers are unaffected by biological agents and daylight. On heating above 200°C, acrylic fibers soften and undergo oxidative attack by a complex mechanism with formation of condensed unsaturated chromophoric (colored) groups within the fiber.
4. Acrylic End-Use Properties
Acrylic has the following properties:
1. Acrylic fibers are usually texturized, they have a bulky, wool-like hand and possess a moderate degree of luster.
2. Staple is common due to its wool-like appearance.
3. Crimping and spinning produces a bulky and resilient product like polyester.
4. High bulking doesn't relate to performance.
5. Yarn weight has to be approximately a similar as wool to perform like wool.
6. They possess fair abrasion and pilling resistance.
7. Bulk and abrasion resistance are kind of like wool.
8. Acrylic fiber possesses sensible resistance to house-hold chemicals and daylight and is moderately resistant to heat-induced oxidation and discoloration.
9. Owing to the introduction of a comonomer, acrylic fibers are generally dyeable and provide quick colours with a large range of dyes including acid, basic, or disperse dyes.
10. The comonomer present determines the type of dye(s) that may be effectively used.
11. Acrylics have poor look retention.
12. There's low static generation.
13. The fibers burn with melting and continue to burn on
14. The acrylic fibers are moderately flammable with a LOI of 18.
15. Acrylics melt at 420*-490°F.
2. Staple is common due to its wool-like appearance.
3. Crimping and spinning produces a bulky and resilient product like polyester.
4. High bulking doesn't relate to performance.
5. Yarn weight has to be approximately a similar as wool to perform like wool.
6. They possess fair abrasion and pilling resistance.
7. Bulk and abrasion resistance are kind of like wool.
8. Acrylic fiber possesses sensible resistance to house-hold chemicals and daylight and is moderately resistant to heat-induced oxidation and discoloration.
9. Owing to the introduction of a comonomer, acrylic fibers are generally dyeable and provide quick colours with a large range of dyes including acid, basic, or disperse dyes.
10. The comonomer present determines the type of dye(s) that may be effectively used.
11. Acrylics have poor look retention.
12. There's low static generation.
13. The fibers burn with melting and continue to burn on
14. The acrylic fibers are moderately flammable with a LOI of 18.
15. Acrylics melt at 420*-490°F.
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