Adhesion between semi-crystalline polymers: grafted PE/EVOH copolymer

Amongst modern polymeric materials, the use of multi-layer structures is becoming popular. This study deals specifically with a five-layer system composed of two outer strata of high-density polyethylene (HDPE) with an inner layer of an ethylene/vinyl alcohol copolymer (EVOH). The further two layers consist of an “adhesive” between the HDPE and EVOH phases: a grafted polyethylene (PE*). We study here the adhesion between EVOH and PE* by means of peel tests. Rate- and temperature-dependent behaviour is described by time–temperature superposition. High values of peel energy are partly attributable to considerable dissipation during elasto-plastic deformation of the peel arm, yet the intrinsic, local adhesion energy is also large. The latter can be partially explained using the Dugdale model, but a second mechanism related to shear would also seem important.