A NANOSCOPIC VIEW OF STRUCTURE AND DEFORMATION OF HARD ELASTIC POLYPROPYLENE WITH SCANNING FORCE MICROSCOPY

Scanning force microscopy (SFM) was used to visualize the surface of h ard elastic polypropylene (HEPP) film. The surface morphology of unstr ained HEPP shows crystalline and noncrystalline rows oriented parallel to the extrusion direction. The crystalline rows are composed of lame llar blocks. The dimensions of crystalline and noncrystalline regions are determined. The structural surface changes induced by stepwise elo ngation of the film with a home-built stretching device are documented by SFM. Stretching of HEPP perpendicular to the extrusion direction c auses cracks advancing through several crystalline rows. During elonga tion parallel to the extrusion direction the separation of adjacent la mellae by their translatory displacement occurs. Deformation-induced s tructural changes of HEPP on the nanometer scale are compared with pro posed deformation models. Nanostructural changes are correlated with c haracteristic variations in the force-elongation curve. (C) 1996 John Wiley & Sons, Inc.