摘要
采用种子乳液聚合法合成了丁苯橡胶接枝聚苯乙烯 (SBR g PS)共聚物 ,将其与高抗冲聚苯乙烯(HIPS)共混 ,研究了共混物的力学性能和微观形态结构。结果发现 ,SBR g PS共聚物能均匀地分散于HIPS基体中 ,其粒径尺寸约为 0 0 5～ 0 15 μm ,HIPS中原有的尺寸为 1～ 4μm的大橡胶子未受破坏 ,形成了大小两种橡胶粒子共存的结构。共混物的冲击强度和断裂伸长率均较HIPS进一步提高 ,而屈服强度未表现出明显下降 ,获得了良好的综合力学性能 ,这表明大小两种橡胶粒子具有显著的协同增韧作用。提出了HIPS的脆 韧转变模型和聚苯乙烯 (PS)增韧的新机理 ,即HIPS中的大橡胶颗粒引发了大量的银纹 ,使相邻银纹间的“基体层”变得很薄 ,分散于HIPS基体中的SBR g PS橡胶小粒子促进了这些很薄的基体层发生屈服形变 ,从而吸收了大量的断裂应变能 。
A series of SBR g PS copolymers were synthesized by grafting styrene onto butadiene co styrene latex rubber particles with seeded emulsion polymerization techniques. After blending these copolymers with high impact polystyrene(HIPS) resins, the mechanical properties and morphology of the blends were investigated. It was found that the SBR g PS elastomer particles are homogeneously dispersed in the HIPS matrix with a particle diameter of 0.05 ～0.15 μm, while the original rubber particles in the HIPS still maintain their primitive size of 1～4 μm. Thus a new HIPS resin with its rubber particle size in a bimodal distribution is obtained. The impact strength of the blends gradually increased with increasing SBR g PS content, but the yield strength of the blends decreased rather substantially. The improved balanced mechanical properties of the blends is considered to be caused by the synergistic toughening of small(0.05～0.15 μm) and large(1～4 μm) rubber particles. Therefore, a brittle ductile transition model for HIPS and a new toughening mechanism of PS are proposed. It is thought that the large number of crazes is nucleated by the large rubber particles of HIPS.The thickness of PS matrix ligament between the neighbouring crazes become smaller, and the SBR rubber particles distributed in the PS matrix promoted shear yielding of the PS matrix ligaments. These processes can significantly absorb tear energy and result in an enhanced impact toughness of HIPS materials.
基金
国家自然科学基金资助项目 (2 0 0 740 38)
