Dynamic mechanical properties of rolled polypropylene sheets

Plastic deformation can be applied to the processing or forming of semi-crystalline polymers. This work concerns the drawing of polypropylene (PP) sheets in order to modify their thermo-mechanical properties. PP sheets were rolled at 110 degreesC to induce molecular orientation. A stable drawing process was carried out experimentally using a single-pass rolling technique. The influences of rolling ratio on the structure, molecular orientation, and thermo-mechanical properties of the sheets was investigated. The original PP sheet was opaque. The rolled PP sheets had smooth surfaces and showed high transparency at high rolling ratios. Dynamic mechanical properties of rolled sheets were evaluated by a non-resonant forced vibration method. The dynamic moduli of rolled sheets increased with increasing rolling ratio. Thermo-mechanical properties were improved by rolling. The improvement in properties can be explained by enhanced molecular chain orientation.