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

Rheological features of melt processed hyperbranched polyesters and their blends are presented in this study. The hyperbranched polyesters showed shear-thinning behaviour for lower generation samples, whilst the higher generation ones exhibited Newtonian behaviour. This distinct shift from shear-thinning behaviour to Newtonian behaviour was also observed in the previous study 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 conditions if at least one of the components is Newtonian. This behaviour is seldom observed in polymer mixtures.