Investigation of barrier properties of as cast and biaxially stretched pet/evoh and peti/evoh blend films

Official URL: http://192.168.1.20/record=b1293651 (Table of Contents)

In this study, poly(ethylene terephthalate)(PET)/poly(ethylene-co-vinyl alcohol)( EVOH) (95/5 w/w) and poly(ethylene terephthalate-co-isophthalate) random copolymer containing 10 wt.% isophthalic acid (PETI)/EVOH (95/5 w/w) blends have been prepared with compatibilizer types as poly(ethylene terephthalate)-cosulfonated isophthalate (PET-co-SIPA), glycol modified poly(ethylene terephthalate) (PETG) and hydroxyl-terminated polybutadiene (HTPB) by using a co-rotating intermeshing twin screw extruder. Cast films have been stretched simultaneously and biaxially 2 and 3 times their original dimensions (λ=2, λ=3). The effects of biaxial orientation, crystallinity, morphology, and chemistry on oxygen gas permeability were analyzed by using different characterization techniques i.e. scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and gas permeability analyzer. After extrusion, the dispersed phase has a particle size of 0.4-0.8 μm without a compatibilizer. Replacing PET homopolymer with PETI has little effect on particle size of the dispersed phase (0.4-0.5 μm) without using a compatibilizer. The smallest particle size of EVOH was 0.17-0.2 μm for PET blends when employed a hydroxyl terminated polybutadiene (HTPB) and 0.15-0.25 μm (glycol modified PET, PETG) and 0.18-0.26 μm (HTPB) for PETI blends. Oxygen gas permeability of the blend films reduces to some extent after stretching. Nonetheless, an increase in oxygen gas permeability has been observed when the results of the neat PET and PETI taken into consideration. This situation results from low degree of crystallinity of the blends. Casted and oriented PET/EVOH films show decreased water vapor permeability values when compared to that of neat PET. The lowest value has been obtained when employed HTPB as the compatibilizer. Casted films of PETI/EVOH blends have higher water vapor permeability values than that of the neat PETI. Water vapor permeability values decrease when films stretched 2 times and 3 times. Nonetheless, comparison of the results together with that of the neat PETI indicates that water vapor permeability values of the stretched films are almost the same as PETI.