Surface studies of UV-irradiated poly(vinyl chloride)/poly(methyl methacrylate) blends

Abstract

Surface properties of poly(vinyl chloride) (PVC), poly(methyl methacrylate) (PMMA) and their blends have been studied using FTIR-ATR spectroscopy, AFM and contact angle measurements. It was found that the surfaces of PVC/PMMA blends were enriched in PMMA, the lower surface free energy component. The results also revealed the existence of weak interactions between the blend components resulting in partial miscibility of system observed for the blends containing below 40% of PMMA.UV-irradiation made the sample surfaces more polar and rough owing to photochemical processes such as oxidation, degradation, dehydrochlorination, depolymerization or etching. The oxidation was more efficient for PVC compared to PMMA. In the case of PVC/PMMA blends, the efficiency of oxidation reactions increased with increasing PVC content and this process was approximately the average of the changes in the pure polymers. The photooxidation reactions were accompanied by degradation reactions leading to formation of low molecular weight oxidized products.AFM studies of UV-irradiated sample surfaces revealed cone-like and globular objects which were easily removed from the surfaces after washing the samples. These objects were made of low molecular weight oxidized material and/or methyl methacrylate. Only neat PMMA surface behaved contrary to all samples. It seemed that irradiation did not yield any changes in surface morphology of PMMA but washed surface of this polymer revealed presence of cone-like structures. It suggests that the mechanism of photooxidative degradation of pure PMMA and PMMA in the blends was different. Probably the presence of chlorine radicals from PVC modifies the route of PMMA photochemical processes in PVC/PMMA blends.