Acrylic fibers chemical resistance

Acrylic fibers are vinyl polymers valued for resistance to chemical and biological degradation. Acrylonitrile (or vinyl cyanide) forms a homopolymer that is used in filters and artificial wool, which is widely used in sweaters. 

Regrettably, a refinery worker was injured by sulfuric acid because a 4-inch (10 cm) piping substitute gasket failed. The acrylic fibers in the nonasbestos gasket material were attacked by the acid. The asbestos fibers had resisted the chemical attack. 

The acrylic fibers exhibit the high strength, stiffness, toughness, abrasion resistance, resilience, and flex life that are associated with the synthetic fibers as a class. They are relatively insensitive to moisture and have good resistance to stains, chemicals, insects, and fungi. Their weatherability is outstandingly good. In continuous filament form, they are considered to have a superior feel. As crimped staple, they are noted for bulkiness and a wool-like hand. ... 

Polyester, epoxies, acrylics, vinyl esters, and silicones have aU been used in pultru-sion, but the largest percentage of the products are vinyl esters and polyesters because of their favorable costs, desirable properties, and easy handling characteristics. Liquid systems with low viscosity are used to ensure rapid saturation of the fiber bundles. The resin determines the weather resistance, thermal resistance, burning characteristics, moisture sensitivity, chemical resistance, and most of the electrical properties. 

The excellent chemical resistance of acrylic fiber stems from its laterally bonded stmctme. Dipole bonds, formed between nitrile groups of adjacent chains. 

Nytril fibers are made up of polymers containing at least 85% vinyli-dene dinitrile units, which appear at least every other unit in the polymer chain. The comonomer used in Nytril synthesis is vinyl acetate. The two monomers are polymerized in benzene using peroxide catalyst. The polymer is precipitated, washed, and dissolved in ], ] -dimethyl formamide and then passed through a spinneret into an aqueous coagulating bath to form Nytril fibers. The properties of the Nytril fiber are similar to the other acrylic fibers. The fiber possesses moderate tensile, regain, and thermal properties. The fiber is chemical and sunlight resistant but is as flammable as cellulosic fibers. Darvan Nytril fibers were produced in the U.S. until 1961. 

The characteristics of fluoropolymers are summarized in Table 1. Thermal and chemical resistance is in general with most of plastics, elastomers and perfluorinated membranes. Weather resistance with the outdoor durability for more than 20 years is specific for fluorinated paint resins. Surface properties such as water and oil repellency are provided by acrylic polymer-based textile finishes and coatings with long-chain per-fluoroalkyl groups. Electrical properties as well as a low refractive index are important for optoelectronics applications like optical fibers. 

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