Performance of multilayer films using maleated linear low-density polyethylene blends

Blends of linear low-density polyethylene (LLDPE) and linear low-density polyethylene grafted maleic anhydride (LLDPE-gMA) were prepared by melt mixing and then coextruded as external layers, with a central layer of polyamide (PA) on three-layer coextruded flat films. Blends with contents of 0% to 55 wt% of maleated LLDPE, on the external layers, were analyzed. The T-peel strength and oxygen and water vapor transmission rate of the films were measured. The surfaces of the peeled films were characterized using attenuated total reflection infrared spectroscopy (FTIR-ATR) and scanning electron microscopy (SEM). The observed increase in T-peel strength of the films with 10% and higher levels of maleated LLDPE in the blend suggests good interfacial adhesion between layers. This sharp increase in peel strength appears to be associated, besides interdiffusion, with specific interactions between polymers, as the bond formation between maleic anhydride and the polyamide end groups by in situ block copolymer formation across the interface. No significant modifications in oxygen barrier properties of the films were observed; however, the use of higher contents of LLDPEgMA, even though it increases the adhesion performance, also increases the water vapor transmission rate by a reduction in the degree of crystallinity.