MICROSTRUCTURE OF QUENCHED AND ANNEALED FILMS OF ISOTACTIC POLYPROPYLENE .1.

The Microstructure of quenched and annealed IPP films was investigated by means of differential scanning calorimetry (DSC), density measurem ents, wide-angle X-ray diffraction (WAXD) and dynamic mechanical spect rometry (DMS). It was found that quenched IPP can be described as a bi phasic material constituted of an amorphous phase strongly cross-linke d by many crystalline entities exhibiting both small size and very low degree of perfection. Such microcrystallites act as true physical tie s of the amorphous phase. On increasing the annealing temperature from 20 degrees C (quenched film) to 160 degrees C, the crystallinity rati o first remained constant for annealing temperatures between 20 and 93 degrees C and then it increased. Subsequently, both size and degree o f perfection of crystalline entities progressively increased and tende d towards the characteristics of the monoclinic phase. This resulted i n a progressive decrease in the physical cross-linking degree of the a morphous phase, even for the samples exhibiting the highest crystallin ity ratio.