In the current research, physical and morphological properties of high-density polyethylene (HDPE) were investigated after equal-channel angular pressing (ECAP) for up to three passes via route A, in which the sample is pressed without any rotation between individual passes, at the temperature of 80 °C. The results of density, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) represent a decrease in the polymer’s crystallinity after deformation, which is more evident after three passes of ECAP. Moreover, a phenomenological mechanism is proposed to explain the variations of crystallinity after ECAP processing. The occurrence of an additional crystalline peak in the XRD pattern, as well as melting doublet in the DSC curve of three-pass ECAP-deformed sample, demonstrate that some part of the initial orthorhombic crystalline phase of HDPE has been transformed to monoclinic crystal structure after ECAP deformation. Furthermore, a reduction in melting temperature and broadening of crystalline peaks show that the thickness of crystalline lamella may decline in one-pass ECAP-deformed sample, which could significantly affect dynamic mechanical behavior of HDPE. In addition, dilatometry results and observation of the impact-fractured surfaces of deformed samples reveal that oriented structures formed in amorphous and crystalline regions of the workpiece.

中文翻译：

---

等通道角压下高密度聚乙烯晶相和非晶相的演变

在目前的研究中，通过路径 A 进行最多三道次等通道角挤压 (ECAP) 后，研究了高密度聚乙烯 (HDPE) 的物理和形态特性，其中样品在各道次之间没有任何旋转的情况下被压制，在 80°C 的温度下。密度、差示扫描量热法 (DSC) 和 X 射线衍射 (XRD) 的结果表明，变形后聚合物的结晶度有所降低，这在 ECAP 三次通过后更为明显。此外，提出了一种现象学机制来解释 ECAP 处理后结晶度的变化。在 XRD 图中出现了一个额外的结晶峰，以及在三遍 ECAP 变形样品的 DSC 曲线中出现了熔化双峰，证明在 ECAP 变形后，HDPE 的初始正交晶相的某些部分已转变为单斜晶结构。此外，熔融温度的降低和结晶峰的加宽表明，单程 ECAP 变形样品的结晶层厚度可能会下降，这可能会显着影响 HDPE 的动态机械性能。此外，膨胀测量结果和变形样品的冲击断裂表面的观察表明，在工件的非晶和结晶区域形成了定向结构。这可能会显着影响 HDPE 的动态机械性能。此外，膨胀测量结果和变形样品的冲击断裂表面的观察表明，在工件的非晶和结晶区域形成了定向结构。这可能会显着影响 HDPE 的动态机械性能。此外，膨胀测量结果和变形样品的冲击断裂表面的观察表明，在工件的非晶和结晶区域形成了定向结构。