Effect of microstructure on crazing onset in polyethylene under tension

Abstract

Abstract The influence of microstructure on dilatation onset is analyzed in polyethylene (PE) under tension. Tests are performed by means of a video‐controlled testing system that gives access to true stress σ 33 —true strain ε 33 curve and records volume strain ε v during stretching. The results indicate that the strain ε (and the corresponding stress σ ) from which viscoplastic dilatation begins depends on microstructural properties of PE. At microscopic scale, materials having a low ε are characterized by inhomogeneous deformation mechanisms leading to pronounced crazing phenomena in amorphous layers. On the contrary, materials having a high ε involve homogeneous deformation mechanisms that limit crazing. These observations are discussed on the basis of crystallinity and tie molecules density. A simple model predicting ε is developed from these microstructural aspects. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers