Correlation between morphology and gas O2 permeability of PP/PLA/EVOH ternary blends

Casting films of polypropylene (PP), poly(lactic acid) (PLA) and ethylene vinyl alcohol copolymer (EVOH) ternary blends having different compositions were prepared. The thermal properties in correlation to the oxygen permeability and mechanical properties of the films were investigated. The morphology of the blends, before and after the film extrusion process was investigated. The SEM images of casted films show a great laminar morphology development in the machine direction (MD). The effects of EVOH and compatibilizer on the relative changes in the crystallization behavior, i.e. melting peak crystallization (Xm) and degree of crystallization (Xc) are considered. While the compatibilization facilitated the crystallization of PP, it had reverse effect on EVOH crystallization. There is an increase in the Xm as well as Xc of EVOH in ternary blend with an increase in EVOH content. The permeability to oxygen was decreased with an increase in EVOH content and compatibilization led to improvement in barrier properties. The crystallinity degree of EVOH revealed to have a greater effect on barrier and mechanical properties as compare to that of PP.