Dynamic Mechanical and X-Ray Studies of Annealed Isotactic Polypropylene

Isotactic polypropylene specimens are annealed at temperatures between 90 and 150°C. Viscoelastic properties are studied by the lateral vibration method. The percent crystallinity and crystallite size are studied by X-ray diffractometry. Annealing at a higher temperature results in a higher density of the specimen. In general more crystallization occurs in the specimen when it is annealed at a higher temperature. Young's modulus is of the order of 10 10 dyne/cm 2 , which increases slightly with the rise in the annealing temperature. The β-peak of the vibration loss tan δ is observed around 10°C. The activation energy of the β-peak calculated from the temperature shift of the peak is 28 kcal/mole for the original sample, and 34–40 kcal /mole and 56–58 kcal /mole for the samples annealed at 90°C and 150°C, respectively.