IMPROVEMENTS OF THE SIMULATION OF SHRINKAGE AND WARPAGE WITH NEW METHODS FOR THE MATERIAL CHARACTERISATION

As simulation programs become more complex, the measurement of material data becomes increasingly important. This is due to the implementation of completely new model formulations - such as for crystallisation and crystallisation kinetics - and the requirements on the precision of rheological and thermal material values as well as the p,v,T-data. A key step in the study of the solidification process of semi-crystalline thermoplastics is presented by the example of isotactic polypropylene. The density of the plastic melt is determined during cooling on basis of X-ray absorption in a test mould built at the IKV. With slow cooling (approx. 3 K/min), it is possible to determine the density profile online and with good time resolution. The attainable time resolution is many times better than for a comparative pressure-volume-measurement recorded on a standard unit for the measurement of the p,v,T-behaviour. With more rapid cooling (approx. 3 K/s) an unusual density profile results in some cases. In future experimental investigations pressure and cooling rate need to be varied over a considerably broader range in order to be able to evaluate the influence of these parameters on the p,v,T-behaviour with a sufficient degree of accuracy.