Poly(vinyl chloride) gelation in rolling process
Polimery 2005, No 6, 441
The course of gelation of suspension poly(vinyl chloride) composition, containing stabilizer and lubricant, in rolling has been investigated (Fig. 1). Effects of time (6-900 s) and temperature (130-200°C) of rolling on the structure, gelation degree (G) as well as mechanical and processing properties [melt flow rate (MFR), tensile strength, impact strength] of the compositions were discussed. Gelation time (tż) was defined as multiplicity of the blend running through the gap between rolls (k) (Table 1). Both optical (Figs. 5-7) and scanning electron microscopy (Fig. 8) helped to evaluate the changes of the structure. It was found that as well temperature of rolling as the gelation time (time of shear forces action) affect significantly the structure of PVC composition. Increase in rolling temperature shortens time to homogeneous rigid film obtaining. It was observed G value was smaller at lower rolling temperature and break-up of the grains of composition was faster (Fig. 9). In higher temperature (up to 180 °C) the disintegration of the grains is slower, but the gelation value is high and therefore the mechanical properties are enhanced (Figs. 10-12). At temperature over 180°C these properties deteriorate because of too big G value.
Key words: poly(vinyl chloride), rolling, gelation degree, structure, properties