Polymer Engineering and Science, Vol.53, No.12, 2573-2581, 2013
Effect of Rolling Temperature on Microstructure and Tensile Properties of Polypropylene
Rolling process was carried out with extruded polypropylene as crystalline polymer at various rolling temperatures, and the rolling characteristics, cross-section morphologies, and tensile properties were investigated. The rolling characteristics were evaluated by springback and dimensional change. The springback increased with increasing rolling temperature. The increment of length was larger than that of width because of the influence of uniaxial drawing by rotation of the rollers. Uniform morphologies were observed at a rolling ratio of 70% and a rolling temperature of 23 degrees C. In contrast, molecular orientation near the surface was higher compared with the inner part when rolled at 70 degrees C. Furthermore, micro spherulitic structures were observed near the surface where recrystallization occurred because of the rising temperature on the specimen surface by friction. Therefore, different morphologies appeared near the surface and in the inner part. Tensile strength was obtained for the rolling direction when rolled at 110 degrees C lower than at other rolling temperatures. It was likely that the molecular orientation was decreased by increasing the springback when rolled at high temperature. (c) 2013 Society of Plastics Engineers