Effect of stirring speed on conversion and time to particle stabilization of poly (vinyl chloride) produced by suspension polymerization process at the beginning of reaction

Abstract

The effect of changes in the stirring speed during suspension polymerization of vinyl chloride monomer (VCM) was investigated near the particle stabilization. Preliminary tests were conducted to check the highest conversion and information regarding the porosity and particle stabilization of two formulations, which are based on different concentrations of initiators and dispersing agents. The influence of stirring speed during the first 2 h of reaction was investigated for the best formulation, indicating that there was a proportional relationship between the increase in speed and the increase in conversion. The results presented suggest that the highest stirring speeds (900 and 1000 rpm) tended to achieve the same conversion with increasing reaction time. This was also observed with the lower stirring speeds (600 and 700 rpm); however, the conversions obtained were lower than those found with higher stirring speeds. The conversions achieved in 20 to 30 min of reaction were similar for all stirring speeds studied (20 min: 4.8% ± 1.3%; 30 min: 7.5% ±1.4%). However, there was greater variation in conversion for longer reaction times (60 min: 15.9 ± 2.8%; 120 min 36.5 ± 2.4%). Stability of the particles was achieved for 6-8% conversion for all stirring speeds used when breakage and coalescence processes stop. The conversion interval obtained in this work was smaller than the values found in the literature (between 15 and 20%). The effect of stirred conditions on particle size distribution showed that better stability of the particle size occurred at 900 rpm for the system studied. In this case, variations in the particle size decreased when the conversion increased.