A miscibility window in PVC/EVA system

The existence of a miscibility window in the PVC/EVA system was investigated using a binary approach. The miscibility window was observed for 45 or 50% to 80% acetate content depending on thermodynamic parameters used. Experimental data on PVC/PVA system give no evidence for the existence of miscibility. The cloud point curves indicated a lower critical solution temperature (LCST) for the PVC/EVA system. This behavior was corroborated using equation of state analysis. Received: 6 December 1996/Revised: 29 July 1997/Accepted: 7 August 1997     

Application of an association model to the PVC/EVA system

A thermodynamic association model was applied to the PVC/EVA system. In this model the enthalpy component is related quantitatively to intermolecular interaction forces. Molecular modeling was applied to obtain the parameters related with interaction forces. The phase diagrams showed lower critical solution temperature (LCST) behavior and also biphasic regions in PVC rich compositions. Received: 7 December 1996/Revised: 1 August 1997/Accepted: 7 August 1997     

Miscibility of PVA/EVA systems by viscometry

Viscometric data were applied to characterize the miscibility of poly(vinyl chloride) (PVC)/poly(ethylene-co-vinyl acetate) (EVA) mixtures using six samples of EVAs with different vinyl acetate content in the copolymer. Relative viscosity vs composition plots showed the imiscibility of PVC/EVA 31 and PVC/EVA 41 blends. The variation of the reduced viscosity, _sp/C with the concentration, C, has been studied for 50:50 by weight blends of PVC/EVA 45, PVC/EVA 45A, PVC/EVA 50 and PVC/EVA 70 in tetrahydrofuran at 25°C. The presence of a sharp crossover and a consequent reduction of slope in _sp/C vs C plots showed that these systems are miscible for a concentration range which corresponds to the regime of dilute solution.     

Polymer-polymer interaction and modeling

The nature of intermolecular interaction in PVC/EVA system was investigated. Bathochromic shifts in infrared region revealed that not only EVA carbonyl but the ester group participates on interaction with PVC chain. These shifts were proportional to acetate content in the copolymer and the composition of EVA in the blend. The PVC group that effectively participates on interaction was not elucidated by infrared spectrometry, but molecular modeling of low molecular weight analogues indicated that hydrogen bonding is the most probable kind of intermolecular interaction present in this system. Received: 7 December 1996/Revised: 1 August 1997/Accepted: 7 August 1997