Deformation of polyethylene by bidirectional cold rolling was investigated. The objective was to better understand the evolution of the hierarchical structure with thickness reduction and the effect on mechanical properties. At a 60% thickness reduction, the thickness recovery after rolling peaked, and the density and crystallinity decreased rapidly resulting in greater optical clarity. Tensile specimens were deformed in uniaxial tension, and it was observed that the yield mechanism shifted from necking and whitening to a diffuse yielding process with extent of rolling. Concomitant greater work hardening, fracture stress, and elastic recovery were also observed upon fracture at both 25 °C and −40 °C. Scanning electron micrographs of the fracture surface revealed discrete buckled microlayers. Furthermore, dynamic mechanical analysis (DMA) revealed the loss tangent peaks associated with the beta and alpha relaxations shifted, suggesting that dilatation rather than compaction was the dominant mode of deformation at 60% thickness reduction.

研究了双向冷轧聚乙烯的变形。目的是更好地了解随着厚度减小的分层结构的演变以及对机械性能的影响。在厚度减少 60% 时，轧制后的厚度恢复达到峰值，密度和结晶度迅速下降，从而导致更高的光学透明度。拉伸试样在单轴拉伸下发生变形，观察到屈服机制从颈缩和白化转变为随着轧制程度的扩散屈服过程。在 25 °C 和 -40 °C 断裂时，也观察到伴随的更大的加工硬化、断裂应力和弹性恢复。断裂表面的扫描电子显微照片显示了离散的弯曲微层。此外，