Rheological behaviour of polymer blends containing only hyperbranched polyesters of varying generation number

Rheological features of melt processed hyperbranched polyesters and their b lends are presented in this study. The hyperbranched polyesters showed shea r-thinning behaviour for lower generation samples, whilst the higher genera tion ones exhibited Newtonian behaviour. This distinct shift from shear-thi nning behaviour to Newtonian behaviour was also observed in the previous st udy for their unprocessed counterparts. This indicates that there is little change in the molecular structures during processing. The striking finding is that the blends consisting of two hyperbranched polyesters showed only Newtonian characteristics in both steady shear and oscillatory shear condit ions if at least one of the components is Newtonian. This behaviour is seld om observed in polymer mixtures. (C) 2001 Elsevier Science Ltd. All rights reserved.