Hydrophobic Zeolite-Filled Polymeric Films with High Ethylene Permselectivity for Fresh Produce Packaging Applications

摘要

Gas permselective plastic films have been in a great deal of attention in the area of modified atmosphere packaging of fresh produces. Such films must allow transport of the respiring gases, i.e. oxygen and carbon dioxide, in a controlled manner and, moreover, should efficiently remove ethylene gas. Therefore, the development of highly permeable films with high ethylene permselectivity, i.e. high in both permeability and selectivity, was carried out. The concept of 'mixed matrix membrane', by which enhanced gas permselectivity can be obtained by incorporation of zeolite particles into the polymeric film, was applied. Fine particles of hydrophobic zeolites, i.e. zeolite beta and ZSM-5, and the surface-modified zeolites were used in this study. The films with uniform distribution of zeolite particles (10% w/w) in 70LDPE/30SEBS (styrene-b-(ethyl-ene-ran-butylene)-b-styrene block copolymer) matrix can be prepared by blow film extrusion. Significantly high ethylene permselectivity, i.e. ethylene permeability of 1.78-2.67 × 10~3 cm~3 • mm/m~2 • day • atm and eth-ylene/O_2 selectivity of 4.67-8.26, was obtained from the films containing octyl-modified and phenyl-modified zeolites. Particular enhancement was observed on the films containing phenyl-modified zeolites. Crystallinity of polyethylene, transition temperatures and decomposition temperature were, however, indifferent among the studied films. Nevertheless, elongation at break and toughness of the films containing surface-modified zeolites were superior. Particle-polymer interface could thus be improved.