Emulsion Polymerization Of Styrene And Methyl Methacrylate Under Pulsed Microwave Irradiation

Emulsion polymerization of styrene and methyl methacrylate were investigatedthrough pulsed microwave irradiation under higher pulse power. The effects of initiatorconcentration, polymerization time, temperature, pulse power, duty cycle, microwaveirradiation energy and pulse width on the conversion and molecular weight were discussed.And the results were compared with those of conventional heating. The results showed:The decomposition rate constant (Kj) of potassium persulfate was increased by a factor of2.4. At the same polymerization temperature and reaction time, reaching 75% conversion,the amount of initiator of pulsed microwave irradiation was reduced 50% comparedconventional heating. At the same initiator concentration, the rate enhancement was 229%(0.10 wt%) and 138% (0.20 wt%) for styrene, and 131% (0.15 wt%) and 158% (0.20 wt%)for methyl methacrylate, respectively. And the molecular weight obtained from pulsedmicrowave irradiation was larger 1.2 times than conventional heating. In 0.2wt% initiatorconcentration, reaching the same conversion, the reaction time of pulsed microwaveirradiation was reduced 34.5% (40% conversion) and 42.2% (75% conversion) for styrene,and 25% (50% conversion) and 47% (75% conversion) for methyl methacrylate, comparedconventional heating, respectively. These results indicated that pulsed microwaveirradiation had significant non-thermal interaction with emulsion polymerization of styreneand the rate of polymerization was increased. Polydispersity indices (DI), the glasstransition temperature (Tg) and tactic index, however, were close. The microstructure andphysical properties of these materials were not modified by the use of pulsed microwaveirradiation. And higher pulse power, larger duty cycle and longer irradiation time mightresult in degradation of polymer. The effect of pulse width on polymerization was small.