Role of an active environment of use in an environmental stress crack resistance (ESCR) test in stretched polyethylene: A vibrational spectroscopy and a SEM study

Characterisation of the role of an active environment of use in an industri al Environmental Stress Crack Resistance (ESCR) test has been carried out d uring the tensile deformation of polyethylene samples. We intended to map t he presence of the active environment within the material using Raman and i nfrared spectroscopy. We found Raman not suitable for the detection of this environment inside the sample while by IR the environment seemed to be pre dominantly present within the transition fronts of the material. A stress-i nduced environment diffusion mechanism is suggested. By scanning electron m icroscopy (SEM) differences in the deformation process between drawing in a ir or in detergent became apparent. These results suggest that the environm ent penetrates into the sample during the necking process, stabilising craz ing. At the molecular level it is likely that chain slip and unravelling of molecular disentanglements are facilitated. All these observations may als o be operative during the ESC phenomenon as samples are subjected to stress , resulting in crazing. (C) 1999 Elsevier Science Ltd. All rights reserved.