Effect of blend composition on the adhesion strength of EVA‐g‐MA/LLDPE‐g‐MA films to epoxy substrates

Abstract

Heat shrink sleeves (HSS) are multilayer polymers that provide corrosion resistance for welding joints of steel pipes. Within the HSS structure, the adhesive layer is a blend of components, such as ethylene vinyl acetate (EVA) and linear low‐density polyethylene (LLDPE). In this study, a systematic approach was employed to investigate the effect of the rheology and blend composition of the maleic anhydride‐modified EVA and maleic anhydride‐modified LLDPE (EVA‐g‐MA/LLDPE‐g‐MA) adhesive layer, prepared by melt processing, on its adhesion properties. Various characterization techniques were employed to investigate the local morphology of the prepared blends at different zones. Peel strength tests were used to characterize the adhesion strength of the prepared adhesives. Our findings demonstrate that the local distribution of EVA‐g‐MA within LLDPE‐g‐MA plays a crucial role in the adhesion strength of the adhesive. The results show that the adhesion strength enhanced by nearly 45% as the composition of EVA‐g‐MA at the surface went up by 20%, shifting the failure location from the epoxy/adhesive interface to the bulk of the adhesive layer. Our hypothesis of the decrease of EVA‐g‐MA intrachain bonding and increase in the EVA‐g‐MA free chain amount in the presence of LLDPE‐g‐MA to improve the adhesion properties was corroborated through our calorimetry results where the relative EVA‐g‐MA crystallinity decreased as LLDPE‐g‐MA was introduced to the blend. The findings of our study highlight the importance of rheological behavior and blend composition in obtaining optimized performance of adhesives within the HSS structure.Highlights Compression molding of EVA‐g‐MA/LLDPE‐g‐MA induces a layered morphology. Local distribution EVA‐g‐MA/LLDPE‐g‐MA components influence their adhesion. EVA‐g‐MA at the interface improves the adhesion of EVA‐g‐MA/LLDPE‐g‐MA. LLDPE‐g‐MA suppresses the EVA‐g‐MA crystallinity. EVA‐g‐MA/LLDPE‐g‐MA composition affects adhesion at different temperatures.