Effect of pressure on the crystallization kinetics of polymers and its consequences for pvT measurements
Sprache des Vortragstitels:
5th International Conference on Polymer Processing and Characterization
Sprache des Tagungstitel:
The influence of both pressure and temperature on the crystallization of an industrial polypropylene was analyzed. The main focus was directed on the spherulitic growth-rate under different pressures and temperatures. In addition also the influence on the nucleation density and on the half-value time of crystallization was investigated. The crystallization experiments were performed using a self-made pressure-dilatometer under pressures between 0.9 and 66.9 MPa and temperatures between 130 ? 150 °C ± 0.5 °C.
The spherulitic growth-rates as well as the numbers of nuclei were obtained through images from a polarizing light microscope of 5 µm thin-sections of the products from the pressure-dilatometer. The numbers of nuclei rise disproportional at the highest pressure (66.9 MPa). This may be explained by the fact that a mixture of monoclinic and triclinic crystals exist in Polypropylene above a formation pressure of 50 MPa. The half-value time of crystallization was obtained through shrinkage curves from the pressure-dilatometer. These were fitted with an Avrami-fit function where the Avrami-exponent n was set as three, caused by a supposed three-dimensional growth. In addition to temperature as determining