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The EVA copolymer which is based on a medium proportion of VA (approximately 4 to 30%) is referred to as thermoplastic ethylene-vinyl acetate copolymer and is a thermoplastic elastomer material. It is not vulcanized but has some of the properties of a rubber or of plasticized polyvinyl chloride particularly at the higher end of the range.
A polymeric foam is a special foam, in liquid or solidified form, formed from polymers. [1] Examples include: Ethylene-vinyl acetate (EVA) foam, the copolymers of ethylene and vinyl acetate; also referred to as polyethylene-vinyl acetate (PEVA) Low-density polyethylene (LDPE) foam, first grade of polyethylene (PE)
In addition to copolymerization with alpha-olefins, ethylene can be copolymerized with a wide range of other monomers and ionic composition that creates ionized free radicals. Common examples include vinyl acetate (the resulting product is ethylene-vinyl acetate copolymer, or EVA, widely used in athletic-shoe sole foams) and a variety of acrylates.
Polyvinyl acetate was discovered in Germany in 1912 by Fritz Klatte. [3] The monomer, vinyl acetate, was first produced on an industrial scale by the addition of acetic acid to acetylene with a mercury(I) salt, [4] but it is now primarily made by palladium-catalyzed oxidative addition of acetic acid to ethylene.
Vinyl acetate is the acetate ester of vinyl alcohol. Since vinyl alcohol is highly unstable (with respect to acetaldehyde), the preparation of vinyl acetate is more complex than the synthesis of other acetate esters. The major industrial route involves the reaction of ethylene and acetic acid with oxygen in the presence of a palladium catalyst. [6]
Ethylene-vinyl acetate (EVA) Various other types of elastomers: Thermoplastic elastomers (TPE) The proteins resilin and elastin; Polysulfide rubber; Elastolefin, elastic fiber used in fabric production; Poly(dichlorophosphazene), an "inorganic rubber" from hexachlorophosphazene polymerization
Theories regarding foam formation, structure, and properties—in physics and physical chemistry—differ somewhat between liquid and solid foams in that the former are dynamic (e.g., in their being "continuously deformed"), as a result of gas diffusing between cells, liquid draining from the foam into a bulk liquid, etc. [1]: 1–2 Theories ...
Coextrusions and laminations are available for specific mechanical and barrier properties for shrink wrapping food. For example, five layers might be configuration as EP/EVA/copolyester/EVA/EP, where EP is ethylene-propylene and EVA is ethylene-vinyl acetate copolymer. [1]