Melting of polymer blends in co-rotating twin screw extruders - Part III: Experimental verification

Experimental studies of the melting process in extruders generally involve a high outlay and can only be performed with certain restrictions, both in respect of the method employed and with regard to the evaluation of the res ults. This part of the work describes one possible way of studying the melt ing of binary incompatible polymer combinations. The method described Makes it possible to estimate the degree of melting of the two components over t he length of the screws of the twin screw extruder Experimental studies wer e performed of polypropylene/polyamide 6 (PP/PA6) blends containing low wei ght contents of the disperse PA 6 phase. In order to verify the theoretical models set out in Part I, page 124 of th is issue, not only were the process conditions of screw speed and throughpu t varied but also the viscosity ratio. This was achieved by using two diffe rent PP grades. In addition, comparable tests were performed on two differe nt sizes of extruders. The tests show that the melting of polymer blends, and particularly the mel ting of the second component, which melts at a higher temperature, is deter mined to a significant extent by the screw rotational speed, the throughput , the ratio of the extruder channel depth to granule diameter and also the material combination (viscosity, ratio). Comparisons of calculations and experiments show, that the melting profiles calculated for different material combinations and process conditions tall y well with the experimental studies in overall terms.