BOPP纵拉过程的应力应变行为

采用高温下挤出厚片纵拉过程的模拟反映出来的应力应变行为，对厚片高温纵拉过程的形变特征进行分析研究，结果表明，EB在加工过程中具有更大的形态能力和更宽范围拉伸速度的适应性，在实验范围内，不同温度下的拉伸屈服应力与对数应变速率均呈线性关系，同时也受到相对分子质量的影响：高温下拉伸比的变化不会改变厚片形变的基本特征，但拉伸比提高后，应力应变曲线后端的硬化现象比较明显；深入理解BOPP拉伸温区结构变化现理，对于提高挤出厚片的形变能力，降低拉伸过程中薄膜的破损，提高生产效率将起到重要作用。

Stress-Strain Behaviors of BOPP Film During MD Stretching

Through simulation of the stretching of extruded BOPP thick sheets in machine direction(MD) stretching and analysis of the corresponding stress strain behaviors,the molecular determined deformation characteristics was investigated.The results showed that with higher content of high molecular weight fraction,exotic EB presented large deformation capacity and flexibility for wider tensile velocities during process;in experimental range,linear relationship exhibited in curves of yield stress versus the logarithm of the strain rates and the yield stress was somewhat controlled by molecular weight;at high temperature the changing of tensile ratios did not change the basic deformation character,but to the end of stress stain curves,obviously hardening occurs which means that the tensile ratio should be controlled in an appropriate range;the processing temperature window of BOPP film being just in the temperature zone of complicated crystallization rate,crystals melting and reorganization and crystalline modifications transformation without clear understanding,deepy investigation of the structures changing mechanisms and accurately controlling of the processing temperature of the machine direction stretching were very important to improve the deformation ability of extruded thick sheets,to reduce the film breakage and evaluate the processing efficiency.