ISOTACTIC POLYPROPYLENE HYDROGENATED OLIGO (CYCLOPENTADIENE) BLENDS .1. THERMAL AND DYNAMIC-MECHANICAL BEHAVIOR OF ANNEALED SAMPLES

Blends of isotactic polypropylene and hydrogenated oligo(cyclopentadiene) were prepared by melting-mixing in a Brabender-like apparatus. Sheets of such blends were moulded under pressure, quenched in water and then annealed for 24 h at 140-degrees-C. Wide angle X-ray scattering was used to examine the effect of the annealing treatment on the quenched specimens. Thermal properties were analysed using a differential scanning calorimeter. Melting points and overall crystallinity content decreased linearly up to a content of 50% in water of HOCP. Beyond such a value a further decrease was observed. Dynamic-mechanical tests were performed at various frequencies (in the range 1 x 10(-2)-75 Hz) and at different temperatures (from -40-degrees-C to 120-degrees-C). The two components appeared to be compatible in the amorphous regions of the system, as already suggested in the literature. In fact a unique peak of the loss modulus versus temperature (which is representative of the glass transition temperature), was always present. Moreover the maximum of the peak was shifted to higher temperatures with increasing oligomer content. The most interesting feature, however, was the change in shape of the whole curve. In fact the peak broadened more and more whereas the height increased only slightly as the oligomer percentage was increased. A tentative explanation is given in the present paper in terms of particular features of the blend morphology, and of a phase inversion at high HOCP content in the blends.