Fibers modacrylic

Modacrylic Modacrylic fibers Modacrylics Modane Modeling Modeling systems Mode-locked lasers Model rocket engines Models... 

Fig. 3. An aqueous dispersion polymerization process used in the manufacture of acrylic and modacrylic fibers.

Acrylonitrile is mainly used to produce acrylic fibers, resins, and elastomers. Copolymers of acrylonitrile with butadiene and styrene are the ABS resins and those with styrene are the styrene-acrylonitrile resins SAN that are important plastics. The 1998 U.S. production of acrylonitrile was approximately 3.1 billion pounds. Most of the production was used for ABS resins and acrylic and modacrylic fibers. Acrylonitrile is also a precursor for acrylic acid (by hydrolysis) and for adiponitrile (by an electrodimerization). 

Acrylic fibers are a major synthetic fiber class developed about the same time as polyesters. Modacrylic fibers are copolymers containing between 35-85% acrylonitrile. Acrylic fibers contain at least 85% acrylonitrile. Orion is an acrylic fiber developed by DuPont in 1949 Dynel is a modacrylic fiber developed by Union Carbide in 1951. 

Dynel, a modacrylic fiber, is produced by copolymerizing vinyl chloride with acrylonitrile. Solution spinning is also used where the polymer is dissolved in a solvent such as acetone. After the solvent is evaporated, the fibers are washed and subjected to stretching, which extends the fiber 4-10 times of the original length. 

The primary use of acrylonitrile is as the raw material for the manufacture of acrylic and modacrylic fibers. Other Major uses include the production of plastics (acrylonitrile-butadiene- styrene (ABS) and styrene-acrylonitrile (SAN), nitrile rubbers, nitrile barrier resins, adiponitrile and acrylamide (EPA 1984). 

Residual acrylonitrile monomer may also occur in commercially-made polymeric materials used in rugs and other products. Estimated levels include acrylic and modacrylic fibers (less than 1 mg acrylonitrile/kg polymeric material), acrylonitrile-based resins (15 to 50 mg/kg), and nitrile rubber and latex (0 to 750 mg/kg) (IARC 1979 Miller and Villaume 1978). It is possible that acrylonitrile may evaporate into air or leach into water from these products, but no data on this topic were located. 

Uses Copolymerized with methyl acrylate, methyl methacrylate, vinyl acetate, vinyl chloride, or 1,1-dichloroethylene to produce acrylic and modacrylic fibers and high-strength fibers ABS (acrylonitrile-butadiene-styrene) and acrylonitrile-styrene copolymers nitrile rubber cyano-ethylation of cotton synthetic soil block (acrylonitrile polymerized in wood pulp) manufacture of adhesives organic synthesis grain fumigant pesticide monomer for a semi-conductive polymer that can be used similar to inorganic oxide catalysts in dehydrogenation of tert-butyl alcohol to isobutylene and water pharmaceuticals antioxidants dyes and surfactants. 

Uses Synthetic fibers and adhesives chemical intermediate in vinylidene fluoride synthesis production of poly(vinyl dichloroethylene) and LLl trichloroethane comonomer for food packaging, coating resins, and modacrylic fibers. 

Fibers with more than 85% acrylonitrile units are called acrylic fibers but those containing 35%-85% acrylonitrile units are referred to as modacrylic fibers. The remainder of the modacrylic fibers are derived from comonomers, such as vinyl chloride or vinylidene chloride, that are specifically added to improve flame resistance. 

Acrylic and modacrylic fibers have a wool-like appearance and feel, and excellent resistance to heat, ultraviolet radiation, and chemicals [Bajaj and Kumari, 1987]. These fibers have replaced wool in many applications, such as socks, pullovers, sweaters, and craft yams. Other applications include tenting, awning fabric, and sandbags for rivershore stabilization. The use of acrylic and modacrylic fibers in carpets is low since these materials do not hold up well to recycling through hot-humid conditions. This also prevents its use in the easy-care garment market. 

An example of this type of a safer chemical is methacrylonitrile (1) compared with acrylonitrile (2) (Figure 1.1). Both compounds are a, 3-unsaturated aliphatic nitriles, and structurally very similar, but 2 causes cancer whereas 1 does not appear to do so. Among other applications, 2 is used in the production of acrylic and modacrylic fibers, elastomers, acrylonitrile-butadiene-styrene and styrene-acrylonitrile resins, nitrile rubbers, and gas barrier resins. In a study conducted by the US National Toxicology Program (NTP) in which 2 was administered orally to mice for 2 years, there was clear evidence that it caused cancer in the treated mice (in addition to causing other toxic effects), and is classified by the NTP as a probable human carcinogen [26]. 

Acrylic and modacrylic fibers are sold mainly as staple and tow products with small amounts ofconltnunus filament liber sold in Europe and Japan. 

Disperse dyes can be used to produce light to medium deep shades on acrylic and modacrylic fibers [96, p. 639], The dyeing mechanism and process correspond to those used on PES and CA fibers (see Section 4.12). However, dyeing can be performed below 100°C. Addition of carriers is not required. The good migration properties of disperse dyes result in problem-free level dyeing. 

Poly (vinyl chloride) fibers (PVC) [96, pp. 642-645], are characterized by their flame retardance. They are dyed preferably with disperse dyes [50, p. 404], [6, pp. 611], As with modacrylic fibers, high temperatures must not be used because of shrinkage of the PVC fiber. Hence, some fibers are dyed at 60-65 °C with dyeing accelerants. Other PVC fibers can be dyed at 100°C without a carrier and a few even at 110°C. Dyes must be selected with regard to the lightfastness desired. 

Modacrylic fibers can also be dyed with disperse dyes, similarly to normal PAC fibers, but the fastness to sublimation is poor (see Section 4.13.3). 

Acrylonitrile resembles VC, a carcinogen, in structure. It is a flammable, explosive liquid (b.p. 77 C, V.P. 80 mm at 20°C). AN is a component of acrylic and modacrylic fibers produced by copolymerization with other monomers, e.g., with methyl acrylate, Me-methacrylate, vinyl acetate, VC and VDC. Other major uses of AN include copolymerizations with butadiene and styrene to produce ABS polymers, and with styrene to yield SAN resins which are used in the manufacture of plastics. Nitrile elastomers and latexes are also made with AN, as are a number of other chemicals, e.g. acrylamide and adiponitrile. Acrylonitrile is also used as a fumigant. 

Halogen-containing fibers namely modacrylics fibers are typically copolymers of vinyl chloride or vinylidene dichloride and acrylonitrile. Although these fibers do not melt-flow or drip, they shrink rapidly when exposed to the fire. Because of this, the best use of modacrylic fibers is in blends. 

Modacrylic Fibers. Commercial modacrylic fibers contain either vinyl chloride or vinylidene chloride copolymerized with acrylonitrile other monomers may also be present (125). The cross-sectional shapes of different modacrylic fibers vary. 

Molecular weight characterization of modacrylic fibers is difficult because of the limited number of solvents available and inhomogeneties in composition between individual polymer chains that affect solution properties, particularly if the comonomers are ionic in character. Di-methylformamide and dimethylacetamide are suitable for measurement of molecular weight of polyacrylonitrile, but errors are introduced when copolymers are analyzed (126). Bortniak et al. (127) have analyzed modacrylic fibers quantitatively in microgram quantities by using pyrolysis gas chromatography. 

Typical physical and chemical properties of commercial modacrylic fibers have been published (125). Modacrylics are not affected by bleaches in the concentrations used for spot and stain removal (31). They are immune to attack by rot, mildew, bacteria, and insects such as moths and carpet beetles (125). Fungi may grow in dirt in an unlaundered Dynel fabric, but washing out the dirt removes the mildew with no effect on the fabric. 

Kennedy, R. K., Modacrylic Fibers, Encyclopedia of Polymer Science... 

In the United States, the modification of PCV has moved in the direction of copolymerizing vinyl chloride with acrylonitrile, or perhaps it should be said that PAN has been modified by copolymerizing the acrylonitrile with chlorine-containing vinyl compounds. In any case, one modacrylic fiber is currently produced in the United States, a modacrylic being defined as containing at least 35 percent but not over 85 percent acrylonitrile. 

The first two modacrylic fibers ever introduced in the United States were Dynel (by Union Carbide) in 1949 and Verel (by Tennessee Eastman) in 1956. The former was a copolymer of 60 percent vinyl chloride and 40 percent acrylonitrile, and the latter was said to be a 50-50 copolymer of vinylidene chloride and acrylonitrile with perhaps a third component graft-copolymerized onto the primary material to secure dyeability. SEF and its version for wigs, Elura , were introduced by Monsanto Fibers in 1972. A few foreign manufacturers are making modacrylic fibers, but the only modacrylic fiber currently in production in the United States is SEF . 

Modacrylic fibers, like acrylic, require after-stretching and heat stabilization in order to develop the necessary properties. It is thought that the stretching is of the order of 900-1300 percent, and that, in a separate operation, shrinkage of about 15-25 percent is allowed during the time that the fibers are heat stabilized. 

The modacrylic fibers, like vinyon and unlike the acrylic fibers, have not become general purpose fibers. They can be dyed... 

A number of copolymers of vinylidene chloride are used in practice. Copolymers with acrylonitrile are used in low flammability fibers (modacrylic fibers). These fibers begin to lose weight when heated at 285-308° C due to dehydrohalogenation [41] but do not ignite easily. A tercopolymer butadiene-styrene-vinylidene chloride is used in fabrics industry and in paper industry. Other copolymers include PVC/PVDC, used for fibers and for films with low permeability to gases and water vapors (barrier films), etc. 

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