Plastic deformation mechanism of crystalline polymer materials during the rolling process

The plastic deformation mechanism of polypropylene during rolling process from entering to exiting of two rollers was investigated by elastic recovery behavior, microstructure, molecular orientation, and crystallinity measurements. During the initial stage of the rolling process, springback increased by about 17 % and during the next stage it decreased as the rolling ratio became greater. Finally, springback became constant below 10 %. Plastic deformation occurred at the surface before the inner part as shown in micrographs. The deformed layer was expanded as the rolling ratio became greater from entering to exiting of rollers. The deformed surface layer led to the high molecular orientation and the crystalline destruction which were investigated by Fourier transform infrared spectroscopy. The anisotropy of molecular orientation was stronger with the rolling processing. Furthermore, this plastic deformation occurred for the whole cross section at the final stage. However, greater molecular orientation and crystalline destruction occurred near the surface than in the inner part.