History of Acrylic

History of Acrylic

Formation of acrylonitrile

Chemistry of acrylics The monomer is acrylonitrile. Another

name for acrylonitrile is vinyl cyanide. The polymer is (PAN) POLYACRYLONITRILE. They go under addition process.

Acrylic Processing In one commercial method, hydrogen cyanide is treated with acetylene:

acetylene + Hydrogen cyanide --> Acrilonitrile In second methodEthylene--Air Oxidation--> Ethylene oxide + HCN--> Ethylene cyanahydrin--Dehydration at 300 °C

(catalyst)--> Acrylonitrile

In a continuous polymerisation process, 95% acrylonitrile and 6% methyl acrylate , 0.25% aqueous solution of K2S2O8, 0.50 % Na2S2O5 solution and 2N sulphuric acid are fed into the reaction vessel at 52°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 The slurry is continuously withdrawn, filtered and washed till it is free from salts and dried.

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 depending on the time of contact in the hot zone, to several times their original length. 

Wet spinning

Dry Spinning

Wet Spinning

The spinning Solution is pumped through fine holes of a jet into a coagulating bath and drawn off as continous filaments which are collected togather to form a continous ‘toe’ or rope of fiber. The bath removes the solvent from the spinning solution leaving acrylic filaments.

Drawing & Washing The fibers are

drawn under heat Washing removes

excess solvent

Drying & Stabalizing The fibers are dried

in a heat chambber.

Controlled heat treatment to prevent subsequent shrinkage.

Crimping Crimping imparts bulk and cover to the

spun yarn and improves fiber to fiber cohesion. This crimp may not be permanent and may not withstand dyeing and finishing.

Cutting Cutting the filaments into the desired

staple length for spinning.

Chemical composition An Acrylic polymer is random copolymer

composed of 2 or more monomers, but by definition, at least 85% of the monomer used must be acrylonitrile.

70-80% crystalline, 30-20% amorphous, excellent alignement orientation. Dégrée of polymérisation is 1000.

The additional monomers are often included in order to confer dye ability:

Vinyl acetate (opens up structure)

Acrylic acid ( provides dye sites)

Chemical properties: Acid – Damaged by strong concentrate acid

and Acrylic has good-to-excellent resistance to strong mineral acids as well as

organic acids. Alkali –Acrylic has fair to good resistance to

weak alkalies and to strong alkalis at room temperature Bleach – Resistance to oxides solvent Organic solvent –In mildew may form on But

surface, But it will have no effect on fabric. In insects acrylic is unaffected by moth.

Chemical properties Light – Acrylic has resistance to light. Its

extreme resistance to such degradation makes it especially useful for

fabrics that will be exposed to sunlight for an extended period of time. . Heat – Acrylic fiber gets tacky at 4550F

(2350C) which is slightly above that of nylon. At higher temperatures, it will melt. Dye – Some times of acrylic are specific to

acid dyes and some to basic dyes

Physical Properties Handle: Acrylic has a warm and dry

hand like wool. Density: 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.

Mositure regain: Acrylic has a moisture regain of 1.5-2% at 65% RH and 70 deg F.

Physical Properties It has a tenacity of 5 gpd in dry state and 4-8

gpd in wet state. Breaking elongation is 15% ( both states). It has a elastic recovery of 85% after 4%

extension when the load is released immediately. It has a good thermal stability. When exposed

to temperatures above 175 deg C for prolonged periods some discoloration takes place.

Acrylic shrinks by about 1.5% when treated with boiling water for 30 min. 

Uses Sweaters Knit garments Faux Fur Coats Pants Skirts Shoe soles Blankets, furniture covers, Hosiery