弱界面无机粒子填充PVC-U形变与韧化的微观机理

Mechanism of Deformation and Toughening of Unplasticized Poly(vinyl chloride) Filled with Inorganic Particles in Weak Interface Adhesion

观测了硬脂酸包覆CaCO3 粒子填充PVC U受力形变过程的相结构演变。至屈服点 ,刚性粒子两极与基体脱开形成孔穴 ;进而通过分子链段的运动 ,基体与孔穴沿外力取向 ;最终因分子链断裂或滑脱 ,孔穴合并迅速扩大 ,并使基材破裂。缺口冲击断裂的机制与拉伸断裂相似 ,大量基体分子沿外力的取向与滑移使材料韧化。弱界面无机粒子的作用在于造成适当尺寸与间距的微孔穴 ,大量基体分子的取向在微穴的诱导下进行 ,由此而使基材韧化。

Structures of PVC filled with submicrometer or nanometer CaCO 3 particles coated with stearate, drawn to various ratios, were observed. At the yield point, rigid particles depart from PVC matrix to form cavities and the matrix is whitening. Then the like crazes are forming while the matrix and cavities are in the direction of drawing. At last, crazes destroy and the matrix fractures. The structure changing in impact test is similar to that in the drawing. It is the forming of a great deal of crazes that toughens PVC. The function of ultrafine particles in weak interface adhesion is to create numerous microcavities, around every of which the stress increases properly. It is these cavities that introduce the matrix orientation and makes PVC toughened.