Introduction
- FTC (Federal Trade Commission) defined acrylic fibers are those containing at least 85% by weight of acrylonitrile comonomer
- Modacrylic is modified acrylic, containing at least 35% but less than 5% by weight of acrylonitrile comonomer
- Produced from solutions either by wet or dry SPG system
- Comonomers are used (at 10:90) ratio
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Acrylic Comonomer ©Textile Pad |
(Vinyl Acetate, Methyl Acrylate)
- Additional comonomers are acrylic acid and sodium vinylbenzene sulphonate.
- Cross-section
- Dry SPG - Dog bone / Dumb-bell shape
- Wet SPG - Kidney / Round shape.
Chemical Synthesis
C2H4O (Ethylene oxide) + HCN (Hydrogen cyanide) → HO-CH2-CH2-CN (Ethylene chlorohydrin)
HO-CH2-CH2-CN (Ethylene chlorohydrin) + KCN (Potassium cyanide) → CH2=CHCN (Acrylonitrile)
n.CH2=CHCN (Polyacrylonitrate)
n = 2000 -5000 nm long.
Fiber Extrusion
- Most acrylic fibers are wet spun (about 85%)
- Sodium thiocyanate + PAN containing methyl acrylate
- A solution in dimethyl acetamide with PAN containing vinyl acetate as a comonomer
- During dry SPG (15%) solution is dimethyl formamide, co monomer is methyl acrylate.
Wet SPG
- Spinneret holes 10,000 -60,000
- Spinneret holes dia 0.05 - 0.38 mm
- The individual filaments emerging from each hole are drawn from the bath together as large filament tows
- After extrusion, all acrylic fibers are washed thoroughly to remove solvents, drawn to increase orientation, dried, and relaxed in either water or steam to improve abrasion resistance and resistance to fibrillation.
Polymer System
- The adjacent polymer chain is strongly Hydrogen bonded between the electronegative nitrogen atoms and the hydrogen atoms on the polymer backbone
- The strong dipole-dipole interaction between them
- CN group of adjacent polymer chains.
PAN Structure ©Textile Pad |
Commercial / Trade Name
- 1952 - Acrilan - Wet spum - USA - Chemstrand
- 1944 - Orlon - Dry spun - USA - Du Pont
- 1952 - Creslan - American Cyanamid
- 1950 - Courtelle - Wet spun -UK.
Tags
Synthetic Fibers