Study On Preparation And Properties Of Permeability LDPE Composite Film

In this paper, by means of melt blending and blowing film forming process, the low density polyethylene (LDPE)/thermoplastic elastomer (TPE) blend films and LDPE/TPE/inorganic particle composite films were prepared. The melt rheological properties, mechanical properties, gas permeation and moisture permeability of films were investigated. The varieties of spherulite morphology of composite films were observed by polarizing microscope (POM). Meanwhile, the crystallization properties and non-isothermal crystallization kinetics were investigated by differential scanning calorimeter (DSC), and the relationship between gas permeation and crystallization properties was analyzed. The details were as follows:By selecting with the ethylene-octene copolymer (POE), ethylene vinyl acetate (EVA) and Ethylene-Propylene-Diene Monomer (EPDM) respectively, the LDPE blend films were prepared. The results show that with increasing content of POE, the tensile strength and elongation at break are increased. Comparison with the others two blend films, the LDPE/POE blend system shows the better mechanical properties. As the content of TPE increasing, the gas permeation and moisture permeability of three kind blend films are increasing tendency. The observations of DSC and POM show that with the addition of POE. EVA or EPDM. the degree of crystallinity of LDPE gets decrease, the formation of spherulite size gets smaller, but more quantity, which contribute to improve the gas permeation and moisture permeability of LDPE film. These correspond to above property test results.Based on mass ratio90/10of LDPE/POE, LDPE composite films respectively with the zeolite molecular sieve (ZMS), diatomaceous earth (DE) or montmorillonite (MMT) were prepared. Along with increasing content of ZMS or DE, the mechanical properties of composite film decrease gradually, but the gas permeation and moisture permeability increased obviously. The mechanical properties of the LDPE composite film filled with MMT presents increased initially and then decreased, the moisture permeability is increased in a certain degree but the gas permeation decreased. Using ZMS with SiO2to composite modified LDPE composite film. As the mass ratio of ZMS/SiO2(75/25). the comprehensive properties of LDPE composite film could be achieved.The observation of POM shows that with the addition of ZMS. DE or MMT. the formation of spherulite size getting smaller. but more quantity. which can help enhance the gas permeation and moisture permeability of LDPE film.By means of DSC method,the non-isothermal crystallization kinetics of LDPE composite films was investigated. By selecting data processing method of Mo ZS and modified Jeziorny, the results indicate that the ZMS, DE or MMT play a role of heterogeneous nucleation agent in the process of crystallization and increased the crystalline rate of LDPE. Especially the LDPE/POE/ZMS composite film, there was outstanding heterogeneous nucleation effect and faster crystalline rate, which is corresponding to the result in properties with higher gas permeation and moisture permeability.