Rotating sector intermittent illumination

The life-time, r, of the radicals can be determined from the ratio of overall rates of polymerization measured at the steady- and unsteady state as a result of intermittent illumination by the rotating sector. In Fig. 3.3-10 the rate constant, kp, of chain propagation (left) and kh that of termination (right), are plotted versus the pressure. Both rate constants increase with increasing temperature. The energy of activation of chain propagation is Ep = 37 kJ/mol, and that of chain termination is E, = 9.9 kJ/mol. The influence of pressure is... 

The data on kp and kt as reported in the literature differ considerably. Therefore, we conducted new studies on methyl methacrylate (MMA), benzyl methacrylate (BMA), and styrene (St) as monomers. The constants were obtained by applying the method of intermittent illumination (rotating sector) combined with stationary state methods. The viscosity of the solvents varied between 0.5 and 100 cP. No mixed solvents composed of low- and high-molecular components were used but pure solvents only, the molecules of which did not deviate very much from a spherical form (methyl formate, diethyl phthalate, diethyl malonate, dimethyl glycol phthalate, etc.). 

The rate of reaction was also studied when the illumination was intermittently interrupted by a rotating sector. When the alternating periods T of light and dark were equal, the relative values r obtained for the rate at 15.9 °C at several values of T are given in table 3. The two entries marked with an asterisk are quoted wrongly in the original publication (private communication from Melville). 

Fig. 3.6.1 Rate of polymerization. A typical dispersion curve obtained by intermittent illumination by means of a rotating sector located between the source of light and the reacting medium.

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