Spontaneous generation of hot and reacted region to form propagating front in a reaction system of free-radical polymerization of methyl methacrylate

摘要

In free-radical polymerizations, Trommsdorff effect and thermal autocatalysis lead to exhibit autoacceleration. As the polymerization proceeds to increase the viscosity of the reaction system, a diffusioncontrolled termination reaction is slowed, while the rate of propagation reaction is scarcely decreased. The total reaction rate is thus increased even if the reaction system is isothermal. However, the temperature of the system usually tend to increase, since the propagation reaction is exothermic reaction. Uncontrollable temperature rise is thus sometimes occurred by synergestic effect of Trommsdorff effect and thermal autocatalysis. This is undesirable for industrial polymerization, since the polymers thus produced are inferior in quality. They tend to have large molecular weight distribution and contain relatively large amount of unreacted monomer. In addition, it sometimes results in reactor explosion. Even though numbers of articles which explained mechanisms of Trommsdorff effect have been published, its combination with thermal autocatalysis to affect the autoacceleration has not been precisely investigated.