Texture evolution of polyethylenes during uniaxial tension

The texture evolution of polyethylenes during uniaxial deformation is investigated using wide angle X-ray diffraction and atomic force microscopy (AFM). A unique feature of this work is that it uses spherical harmonic method in texture analysis to obtain recalculated pole figures and orientation distribution function plot of polyethylenes during texture evolution. Another important feature of this work is the in-situ characterization using a combination of X-ray and AFM techniques. The process of uniaxial tension and strain relaxation are isolated while most previous works used the relaxed samples in their studies. After uniaxial extension, persistent texture components together with non-persistent ones are developed in the high density polyethylene (HDPE). It is observed that the relaxation process strengthened the c-axis component while mitigating or eliminating other preferred texture components. The texture evolution of a linear low density polyethylene (LLDPE) during uniaxial extension is quite different from that of HDPE. The deformed texture in LLDPE showed a strong (100)[001] texture component and some weak components. Furthermore, there was no change in texture after the sample was allowed to relax in contrast to HDPE. The differences in the texture evolution are related to the stress relaxation behavior of these two materials. After the sample is released, HDPE will continue to relax resulting in a change in texture. Based on the results of the present study, an attempt is made to propose the deformation mechanisms in polyethylene materials. In HDPE lamella stack rotation and lamellar separation are dominant while in LLDPE interlamellar slip becomes the dominant mode of the deformation. The morphology evolution observed by atomic force microscopy are in agreement with the texture analysis.