ADHESION IMPROVEMENT BY UV GRAFTING ONTO POLYOLEFIN SURFACES

High Density Poly(ethylene) (HDPE) and Poly(propylene) (PP) were subje cted to several surface treatments, namely UV grafting of hydroxyethyl methacrylate (HEMA), plasma deposition of HEMA and oxygen plasma treat ment. Treated surfaces were subjected to two post-treatment routines ( extraction with ethanol and high temperature aging). The effect of the se treatments on the adhesion of HDPE and PP to epoxy coated studs was evaluated by a pull test. No adhesion at all was recorded on untreate d samples. On the other hand, all the treatments yield high bond stren gth in the case of HDPE: an average bond strength of about 290 kg/cm(2 ) and of about 200 kg/cm(2) was observed after UV grafting and plasma treatments. The treated samples were practically insensitive to post-t reatments. As to PP, Which undergoes chain scission in plasma, it is b est treated by the comparatively milder conditions of UV grafting, whi ch yields an average bond strength similar to that observed on HDPE. O -2 and HEMA-plasma-treated PP show a mean bond strength close to 50 kg /cm(2), and are deeply affected by the post-treatment routines.