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

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

Effect of organoclay on the physical properties of UV-curable coatings

The combination of UV-curing and nanocomposite technology has been studied to produce cost-effective coatings with superior physical and mechanical properties. The clay was modified with dimethyl dihydrogenated-tallow quaternary ammonium salt and made organophilic. The effect of the organoclay(2-10 phr) on curing rate, mechanical, thermal and physical properties of a urethane-acrylate coating has been determined. X-ray diffraction analysis, AFM, SEM and TEM images as well as the tensile properties of different formulations have confirmed the uniform distribution of organoclay in polymer matrix. At 3 phr organoclay addition, the UV-cured film exhibited the best mechanical performance due to the formation of both intercalated and exfoliated morphologies. Curing time was reduced and the initial thermal decomposition temperature shifted 50°C to higher temperature by the incorporation of small amount of organoclay. The nanocomposite coating was also found to be more resistant against scratching compared with clay-free coating

Oxygen gas and water vapor permeability of biaxially stretched poly(ethylene terephthalate)/poly(ethylene-co-vinyl alcohol) and poly(ethylene terephthalate-co-isophthalate)/poly(ethylene-co-vinyl alcohol) blend films

In this study, poly(ethylene terephthalate)(PET)/poly(ethylene-co-vinyl alcohol) (EVOH) and poly(ethylene terephthalate-co-isophthalate) (PETI)/EVOH (95/5 w/w) blends have been prepared with different types of compatibilizers using a co-rotating intermeshing twin screw extruder. Cast films have been stretched simultaneously and biaxially 2 and 3 times their original dimensions. Scanning electron microscopy, differential scanning calorimetry, oxygen gas and water vapor permeability analyzers have been employed for establishing the relationships among biaxial orientation, crystallinity, morphology, and chemistry on oxygen gas and water vapor permeability. The lowest oxygen gas and water vapor permeability values have been obtained when employed hydroxyl-terminated polybutadiene as the compatibilizer

Improvement in gas permeability of biaxially stretched PET films blended with high barrier polymers: The role of chemistry and processing conditions

Improvement in oxygen gas barrier properties of polyester/polyamide blends used in packaging industry is the main objective of the present study. For this purpose poly(ethylene terephthalate) (PET)/poly(m-xylene adipamide) (nylon-MXD6) (95/5w/w) and poly(ethylene terephthalate-co-isophthalate) copolymer (PETI)/MXD6 (95/5w/w) blends have been prepared with a PET copolymer which consists of 5wt.% sodium sulfonated isophthalate (PET-co-5SIPA) as compatibilizer and a carboxyl-terminated polybutadiene (CTPB) as filler by using a co-rotating intermeshing twin screw extruder. The effects of chemical architecture and morphology on oxygen gas permeability and processability were analyzed by using a range of characterization techniques including differential scanning calorimetry (DSC), scanning electron microscopy (SEM), oxygen gas permeability analyzer, and a special computer controlled uniaxial stretching system that provides real-time measurement of true stress, true strain and birefringence. The morphological analysis revealed that PET-co-5SIPA was an effective compatibilizer for both PET/MXD6 and PETI/MXD6 blends. DSC analysis and spectral-birefringence technique were used to understand the thermal and stress-induced crystallization behavior of the blends. Morphological analysis of the films after biaxial stretching indicated that the spherical nylon phase was converted to 75nm thick disks during stretching (aspect ratio L/W=6) that creates a tortuous pathway for oxygen ingress. Stretching enhanced the barrier properties of PET/MXD6 and PETI/MXD6 blends