Ethylene vinyl acetate branch-points

Polyethylene blends having toughness and elastic recovery comparable to those of plasticized PVC comprised >50 wt% of a copolymer of ethylene and either butene or hexene [LLDPE, p = 880-915 kg MI < 1 dg min , long-chain branching =0.5-1.5 long chalns/l.OOOC, M > 200 kg mol ] >5 wt% of a copolymer of ethylene and either vinyl acetate or ethyl acrylate, EVAc or EEA and 5-30 wt% liquid hydrocarbon oil. The blends showed essentially no yield point and behavior similar to that of cross-linked materials, although they were not cross-linked (strain recovery). They were found competitive with plasticized PVC in terms of both physical properties and economics... 

Backbiting is an intramolecular chain transfer reaction. If transfer reactions occur between different chains, long-chain branched polymers are formed. Well-known examples include ethylene and vinyl acetate. Vinyl acetate polymerization could lead to gel formation under certain conditions. It should be pointed out that chain transfer to polymer reaction alone generates only T-type branch structures that do not result in gel formation. Theoretically, some mechanism such as radical termination by combination that brings two chains together to form H-type branch structures is an essential condition for gelation. 

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