Editing Polyethylene (section)

=== Ethylene copolymers with unsaturated esters ===
If unsaturated esters are copolymerized with ethylene, either the alcohol moiety may be in the polymer backbone (as it is the case in ethylene-vinyl acetate copolymer) or of the acid moiety (e. g. in ethylene-ethyl acrylate copolymer). [[Ethylene-vinyl acetate]] copolymers are prepared similarly to LD-PE by high pressure polymerization. The proportion of comonomer has a decisive influence on the behaviour of the polymer.

The density decreases up to a comonomer share of 10% because of the disturbed crystal formation. With higher proportions it approaches to the one of [[polyvinyl acetate]] (1.17 g/cm<sup>3</sup>).<ref name="Domininghaus" />{{rp|235}} Due to decreasing crystallinity ethylene vinyl acetate copolymers are getting softer with increasing comonomer content. The polar side groups change the chemical properties significantly (compared to polyethylene):<ref name="Kaiser" />{{rp|224}} weather resistance, adhesiveness and weldability rise with comonomer content, while the chemical resistance decreases. Also mechanical properties are changed: stress cracking resistance and toughness in the cold rise, whereas yield stress and heat resistance decrease. With a very high proportion of comonomers (about 50%) rubbery thermoplastics are produced ([[thermoplastic elastomer]]s).<ref name="Domininghaus" />{{rp|235}}

Ethylene-ethyl acrylate copolymers behave similarly to ethylene-vinyl acetate copolymers.<ref name="Kaiser" />{{rp|240}}