Microstructural Evolution and Its Effect on Mechanical Properties of Isotactic Polypropylene by Shear Plastic Deformation at Elevated Temperatures

作者：Wang, Ting Lan; Tang, Song Chao^*; Chen, Jian Ding

来源：Journal of Macromolecular Science Part B-Physics, 2015, 54(11): 1309-1322.

DOI：10.1080/10926771.2015.1081119

• equal channel angular extrusion
• extrusion temperature
• isotactic polypropylene
• orientation
• shear
• spherulite

Isotactic polypropylene (iPP) was plastically shear deformed by equal channel angular extrusion (ECAE) at extrusion temperatures varied from 45 to 125 degrees C (25 mm/min). The evolutions of morphology and crystal orientation were studied by reflected optical microscopy (ROM), scanning electron microscopy (SEM), and X-ray diffraction. It was found that the original spherulites were deformed into nearly ellipsoids with their long axis tilted at an angle away from the flow direction. Azimuthal scanning results revealed that two preferred crystal orientations were formed after ECAE. The crystal plasticity was activated by increasing the extrusion temperature, followed by fast rotation of crystallites toward the shear direction. The thermal mechanical analysis (TMA) indicated that low extrusion temperature was favorable to fix the molecular orientation. The iPP samples processed at the investigated temperatures displayed a significant increase in the impact strength, especially for those extruded at 45 degrees C and 65 degrees C. The tensile results revealed a greater elongation at break in the samples deformed at low temperatures (45 degrees C and 65 degrees C) but not in those deformed at high temperatures (85 degrees C or above).

• 出版日期2015
• 单位华东理工大学