Wu Xiangji, Pu Lin, Xu Yunfei, Shi Jinchun, Liu Xiaoyi, Zhong Zhengye, Luo Sheng-Nian
The Peac Institute of Multiscale Sciences Chengdu Sichuan 610031 People's Republic of China
Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University Chengdu Sichuan 610031 People's Republic of China
RSC Adv. 2018 Jun 20;8(40):22583-22591. doi: 10.1039/c8ra03366h. eCollection 2018 Jun 19.
The effect of high strain rate and large shear deformation on the orientation of crystallites in high density polyethylene (HDPE) was investigated with dynamic equal-channel-angular pressing (D-ECAP). The HDPE samples were processed by two loading routes, route A and route C. Grid lines were used to obtain macroscopic strain distributions, which were substantiated by finite element modeling. Owing to the strain rate effect, the number of D-ECAP processing passes has a minor effect on the shear strain accumulations compared to ECAP. D-ECAP leads to a decrease in the thickness of the crystalline stem, and the crystallinity. After route-A or route-C D-ECAP processing, a new monoclinic phase emerges, and two types of crystallographic -axis orientations appear: the crystallographic -axis is approximately parallel to the flow direction (FD), or is tilted at approximately 55° clockwise away from FD. However, only one type of crystallographic -axis orientation is detected after 2 passes of route-C D-ECAP. It is viable to utilize D-ECAP to control the structure and orientation of crystalline polymers, as a complement to ECAP and other processing techniques.
采用动态等径角挤压（D-ECAP）研究了高应变速率和大剪切变形对高密度聚乙烯（HDPE）中微晶取向的影响。HDPE样品通过两种加载路径，即路径A和路径C进行加工。使用网格线来获得宏观应变分布，这通过有限元建模得到了证实。由于应变速率效应，与等径角挤压（ECAP）相比，D-ECAP加工道次对剪切应变累积的影响较小。D-ECAP导致结晶茎厚度和结晶度降低。经过路径A或路径C的D-ECAP加工后，会出现一种新的单斜相，并且出现两种晶体学轴取向：晶体学轴大致平行于流动方向（FD），或者顺时针倾斜约55°远离FD。然而，在路径C的D-ECAP经过2道次后，仅检测到一种晶体学轴取向。利用D-ECAP来控制结晶聚合物的结构和取向是可行的，作为ECAP和其他加工技术的补充。
