호모-폴리프로필렌/폴리스티렌 블렌드의 조성비에 따라 변하는 발포체의 모폴로지와 물성 연구

Abstract

Polypropylene is obtained by polymerizing propylene obtained by decomposing naphtha in a petrochemical plant with Ziggler-Natta catalyst. It has low specific gravity and is a crystalline resin with high tensile strength, high hardness and excellent heat resistance. In particular, foams made of polypropylene have an advantage of being superior in heat resistance, heat insulation, chemical resistance and physical properties to other plastic foams. However, polypropylene, especially homo-polypropylene, has difficulties in forming foams because the Tm is high and the range of temperatures having suitable rheological properties for forming the foam is narrower than for other foams. This is because when the processing temperature is higher than Tm, the melt viscosity drops sharply, which is caused by the high crystallinity of the polypropylene. In this study, PS(polystyrene) with low crystallinity was blended with homopolypropylene to improve the melt viscosity which dropped rapidly. SEBS was added as a compatibilizer to improve the compatibility of the two polymers. The effect of the amount of SEBS on the crystallinity was investigated. Thereafter, polypropylene, polystyrene, a compatibilizing agent and an additive including a blowing agent were added to the extruder by dry blending, and a foam was formed by an extrusion foaming process. The morphological changes observed by the composition ratio of blowing agent and base polymer and the amount of compatibilizing agent were observed through a microscope and various physical properties were measured to investigate the correlation of physical properties varying with the morphology of the foam.