RHEOLOGICAL PROPERTIES OF GRAFT-COPOLYMERS IN POLYMER BLENDS - INFLUENCE OF THE ENTANGLEMENT DENSITY OF THE BACKBONE AND THE MOLECULAR-WEIGHT OF THE GRAFTS

The feasibility of the graft reaction in the melt at the interface bet ween one-end amino-functionalized polystyrenes and random poly(styrene -co-maleic acid anhydride) has been demonstrated by Fourier transform IR spectroscopy through the presence of the characteristic C = O imide band in the IR spectrum. The influence of the graft copolymer on the theological properties was studied by dynamic mechanical spectroscopy. Using a series of model blends, it has been shown that the polymer ba ckbone has the predominant influence on the theological properties. On ly if the backbone entangles are important additional elastic contribu tions observed. If the backbone is below the critical fraction from en tanglement formation, the attached grafts retard the flow, but the inc rease of the elasticity is less important. Thus, to assure compatibili zing effects of grafted copolymers, both the molecular weight of the g rafts and the weight fraction of the backbone have to fulfil the given entangling conditions.