Polyvinylchloride glass transition temperature

It can be seen that the temperature sensitivity drops dramatically (several decades) when T-Tg increases. The closer a polymer is to its glass transition temperature, the larger the temperature sensitivity of the viscosity. This explains why polymers whose normal process temperatures are close to their glass transition temperature exhibit a high temperature sensitivity in processing. Examples are polystyrene, polyvinylchloride, and polymethyl methacrylate. In general, polymers that are processed considerably above their glass transition temperature (more than 150°C above Tg) show a relatively small temperature sensitivity. Examples are polyethylene, polypropylene, and polyamide. 

Several thermoplastics, both of the commodities kind [polystyrene (PS), polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), polypropylene (PP), polyvinylchloride (PVC) etc.] and engineering pol)uners [polyamides (PA), polyesters (PE), polycarbonates (PC), polyimides (PI), polysulfones (PSF), polyoxymethylene (POM), polyphenylene oxide (PPO) etc.] exhibit glass transition temperatures (Tg) higher than or close to room temperature (R.T.). As a consequence they show, at R.T. or below it, the shortcoming of brittle impact behaviour, which limits their commercial end-uses. 

Figure 5.5 Effect of chlorine content on the glass transition temperature of chlorinated polyethylene. Data for polyvinylchloride (PVC) and polyvinylidene chloride (PVDC) are shown for comparison. Drawn after data from Schmieder and Wolf (1953).

Chapiro [357] has shown that polyvinylchloride predominantly crosslinks. A value of 2.15 was determined by Wippler [358] for GCL at room temperature. Values of GCl were measured by Pravednikov et al. [359] over a wide temperature range. An Arrhenius-type plot of the Gc L values gives an activation energy of 11 kcal mole-1 above the glass transition... 

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