Autoadhesion of high density polyethylene (HDPE) to HDPE by ultraviolet grafting of methacrylates and acrylates

Abstract

A study has been made on the effect of the presence of grafted acrylic layers on the autoadhesion of polyethylene. Methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), and butyl methacrylate (BMA) were grafted onto high density polyethylene (HDPE). The grafting reaction was faster at higher temperature and methacrylates graft more easily than acrylates. For methacrylates and acrylates, the grafted amount increases with increasing length of the pendant alkyl chain. The grafting temperature is a crucial factor affecting the adhesion of grafted PE samples. For the samples grafted at lower temperature (in a room temperature water bath), the adhesion is very low (less than 50 N/m), even for very thick grafted layers. But for the samples grafted at higher temperature, much higher adhesion can be obtained. The presence of homopolymer was another factor affecting the adhesion of PE samples. When homopolymer is removed from the surface of the grafted sample, higher adhesion can be obtained. For some samples, the highest peel strength of more than 1000 N/m has been obtained. The low adhesion of the samples grafted at low temperature is attributed to the high branching of grafted chains.