Preparation And Properties Of Dioxane Plasticized Microcellular PET Sheet By Compression Molding

Polyethylene terephthalate(PET) sheets were plasticized with dioxane as plasticizer for subsequent process, the effects of plasticization time and plasticization temperature on the content of plasticizer were investigated, the migration rate of plasticizer under different condition and the effect of the content of plasticizer on the crystallization property, mechanical properties and dynamic mechanical properties were studied. Plasticized PET sheets were microcellular foamed by compression molding and the effects of foaming temperature, foaming pressure and plasticizer content on the cell structure and tensile mechanical properties were investigated. The effect of plasticizer content on the dynamic mechanical properties of PET sheets were studied, the mechanical properties and glass transition temperature (Tg) of PET sheets before and after plasticization were compared. The experimental results were conducive to the preparation of microcellular foaming materials with better properties, and enriched the theoretical foundation of compression molding.Plasticized PET sheets were successfully prepared by controlling of plasticization temperature and time in this paper before being characterized. The results showed that plasticizer content rose with increasing of plasticization temperature and time; the plasticizer exerts certain mobility in air, white oil and deionized water, The surface of PET sheets existed some micropores when the content of plasticizer was higher than5%, and water uptaking phenomenon was obvious when PET sheets were immersed in deionized water. With increasing of content of plasticizer, the Tg of plasticized PET sheets, storage modulus at100℃, tensile strength and elongation at break of plasticized PET sheets all decreased. The content of plasticizer slightly influenced the degree of crystallinity without obvious variation trend.Microcellular foaming plasticized PET sheets were prepared successfully by compression molding after plasticization with azodicarbonamide as foaming agent, the foaming structure and mechanical properties of the PET sheet were investigated. The results showed that the cells of the sheet were all closed pore structure with irregular shape; the cell size rose with increasing of foaming temperature and plasticizer content, and decreased rose of foaming pressure; the cell density and relative density decreased with increasing of foaming temperature and plasticizer content, and rose with increasing of foaming pressure.The tensile strength, tensile modulus and elongation at break all dropped with increasing of foaming temperature and plasticizer content, and rose with increasing of foaming pressure.The glass transition temperature of the sheets decreased with increasing of plasticizer content. Comparing with the plasticized PET sheet before microcellular foaming, the Tg of plasticized PET sheets was lower, while tensile strength and elongation at break was higher with gentle fluctuation with the variation of content of plasticizer.