IR spectroscopy and X-ray diffraction analysis of industrial polyvinyl chloride suspension

Abstract

In terms of the contemporary plastic industry, world production of polyvinyl chloride is second only to polyolefins. Recyclable by almost all known methods, polyvinyl chloride offers high strength, good insulating properties, as well as resistance to acids, oxidising agents and solvents. At the same time, the ability to process polyvinyl chloride into products is limited by its lack of stability at high melt viscosity temperatures, since hydrogen chloride released during its heating catalyses further process of polymer decomposition. Thus, due to the softening temperature of polyvinyl chloride being higher than its decomposition temperature, it cannot be processed in its pure form. Consequently, functional polyvinyl chloride-based materials tend to be composites. By varying the composition of mixtures, plastic masses characterised by either very soft (plastic compounds) or hard (vinyl plastics) structures can be obtained. The properties of polyvinyl chloride-based polymer products are largely determined by the structure and morphology of the polymer. In the present work, the properties of industrial suspension polyvinyl chloride (Sayanskkhimplast JSC, Irkutsk Oblast) were studied in detail for the first time. The molecular weight of the polymer determined by the viscometric method was 1.0 · 106. Thermogravimetric analysis showed that polyvinyl chloride mass loss started to occur at 160 °C. Following the complete IR band assignment of the polymer, the polyvinyl chloride under study was established to contain no foreign substances (impurities of stabilisers, emulsifiers and additives). The diffraction curve of the polymer was established to be qualitatively similar to equivalent partially crystalline polymers. Two amorphous halos were detected at 2θ of 24° 30′ and 39° 30′ below a group of crystalline peaks. The crystallinity degree of polyvinyl chloride was determined and mechanisms for the formation of its regular and irregular structure were proposed.