Makoto Kudo

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 17xa0% and during the next stage it decreased as the rolling ratio became greater. Finally, springback became constant below 10xa0%. 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.

Morphology Change of Extrusion Molded Crystalline Polymer by Rolling Process

In this work, the spring back, dimensional change, internal structure and morphology of extruded polypropylene were investigated in order to consider the rolling characteristic. It was found that the internal structure, molecular orientation and crystallinity were changed a little by high spring back under low reduction in thickness. Crystal structure was extended along the rolling direction with high reduction in thickness due to the increase of plastic deformation. As a result, molecular orientation increased and crystallinity decreased at over 30% of reduction in thickness. Crystalline structure of surface was similar to the center part in cross-section at 70% reduction in thickness, and molecular orientation was constant.

Mechanical Properties and Morphology of Poly(Lactic Acid) Composites with Oyster Shell Particles

The biodegradable composites were prepared with the oyster shell particles (OSP) and poly(lactic acid)(PLA) by injection molding. The mechanical and thermal properties were investigated. The degradation temperature of the composites decreased by increasing the content of OSP compared with PLA. From the results of tensile test, the tensile strength and the fracture strain of the composites decreased because of exist of OSP. However, the Young’s moduli of the composites increased compared with PLA. The SEM observation of morphology confirmed that the interface between PLA and OSP had poor adhesion.