Witold Brostow and Nandika Anne D'Souza
Laboratory of Polymers and Composites
Department of Materials Science
University of North Texas
Denton, TX 76203-5308
Faculty of Chemistry
Rzeszow University of Technology
35-959 Rzeszow, Poland
A. C. Ramamurthy
Automotive Components Group
Ford Motor Co.
24300 Glendale Avenue
Detroit, MI 48239
Recent theoretical evidence indicates that the effects of quenching seen in the isothermal crystallization kinetics can be eliminated through use of a nonisothermal method based on constant rate heating and cooling through inclusion of an activation energy. To investigate the potential of this method for polymers, we apply it to semicrystalline polymers: polypropylene (PP), a binary blend PP + ethylene propylene diene rubber (EPDM) and a ternary system PP + EPDM + high-density polyethylene (HDPE). As opposed to traditional rubber-modified systems such as high-impact polystyrene (HIPS) wherein an amorphous component is blended with a rubbery one, the PP + EPDM system has a semicrystalline component. From the perspective of crystal lamellae growth or stress induced slip, the thermophysical properties are also a concern. Therefore, we use differential scanning calorimetry (DSC) and thermomechanical analysis (TMA). The results indicate that differences between isothermal and nonisothermal conditions must be taken into account since the latter conditions previal in extrusion, injection molding, and in hot coating-slow cooling processes. Our nonisothermal analysis of crystallization should assist in the optimization of cooling of semicrystalline polymers.
*Polymer Eng. & Sci. 1996, 36, 1101.