Polyacrylonitrile film properties

Watanabe62) studied systematically the copolymerization of ra-methacryloyl-polyoxyethylenes, with monomers such as acrylonitrile, styrene, butyl methacrylate, and methacrylic acid. It should be mentioned that the macromonomers that he prepared are very short so that no difficulties were encountered to isolate the graft copolymers formed. There are many applications for these graft copolymers, e.g. as additives in polyacrylonitrile films and fibers they cause improved antistatic properties. They have been tested as varnishes, coatings, and wood dimensional stabilization agents. 

Polyacrylonitrile (PAN) films have outstanding oxygen and CO2 barrier properties, but only modest water-vapor barrier properties. They are for processed-meat and fresh pasta packaging laminations where an oxygen barrier is required for vacuum or gas flush packaging. 

No amount of sterilization wiU prevent or even slow autooxidation, and there are only two defenses removal of O2 and addition of inhibitors. Oxygen barriers in food packaging are a major topic in the engineering of polymer films. The barrier properties of various polymers are very important in food applications, and many of these are multilayer polymers that have a thin layer of an impermeable polymer (such as polyacrylonitrile and ionic polymers) on a cheaper but O2-permeable polymer such as a polyolefin, which gives mechanical strength to the fikn. 

It Is known that most radiation Initiated polymerization processes are Initiated by Che free radicals created by radlolysls of Che monomers. If a monomer or a mixture of monomers Is Irradiated In Che presence of a polymer, a graft copolymer Is formed which has different physical properties. For example. If a second polymer like polyacrylonitrile or polyvlnylldlne chloride, which possess superior barrier properties against permeation by oxygen, carbon dioxide, water vapor etc.. Is grafted to a polyolefin film like polyethylene, polypropylene, etc., the barrier properties of the composite film are greatly enhanced compared with Che polyolefin film. 

Alkali and acid treatments have also been used to modify surface properties of polymers sulfonated polyethylene films treated first with ethylenediamine and then with a terpolymer of vinyhdene chloride, acrylonitrile, and acrylic acid exhibited better clarity and scuff resistance and reduced permeabihty. Permanently amber-colored polyethylene containers suitable for storing light-sensitive compoimds have been produced by treating fluorosulfonated polyethylene with alkali. Poly(ethylene terephthalate) dipped into trichloroacetic/chromic acid mixture has improved adhesion to polyethylene and nylons. Antifogging lenses have been prepared by exposing polystyrene films to sulfonating conditions. Acid and alkali surface treatments have also been used to produce desired properties in polymethylmethacrylates, polyacrylonitrile, styrene-butadiene resins, polyisobutylene, and natural rubber. Surface halogenation of the diene polymers natural rubber and polyisobutylene resulted in increased adhesion to polar surfaces. 

Mechanical properties are important for the practical use of blend fibers. Usually, the poor compatibility of the component polymers may result in extremely low tenacity of the blend fibers. Literatme reports [140] that the tenacity of cellulose/chitosan blend films increased up to a 20% chltosan content, which was explained by the occurrence of specific interactions between cellulose and chitosan molecules. Improvement of tenacity and of the initial modulus of blend fibers may therefore be attributed to the presence of the interactions between cellulose and chitosan molecules in the fibers. Also, the cellulose and polyacrylonitrile (PAN) molecules form miscible blend pairs in the dimethylacetamide-LiCl solvent system, their miscibility being due to the specific interactions between a hydroxyl group of cellulose and a nitrile group of PAN. 

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