On the polymerization of formaldehyde in the liquid state. II. Gamma ray‐initiated polymerization in a dispersed system

Abstract This paper presents a discussion on the kinetics of formaldehyde polymerization in a dispersed system under 60Co‐γ‐irradiation. Polymerization took place at −80°C. in methylcyclohexane and n‐heptane, using sorbitan sesquioleate as nonionic detergent. The initial rate of polymerization is little dependent on the concentration of detergent within the concentration range investigated, on the type of dispersion medium. Namely, the process is unaffected by the size and number of the monomer droplets. The intensity exponent is close to 0.9 and the molecular weight of the polymer is little affected by dose rate. These facts lead to the reasonable conclusion that almost all the active centers are generated in the monomer globules and that in the polymerization unimolecular termination is operative. Both the initial rate of polymerization and average degree of polymerization are little dependent on the amount of monomer within a certain range. However, the polymerization rate increases rapidly with increasing amount of monomer beyond about 60 wt.‐% and approaches that of bulk polymerization. The average degree of polymerization tends to diminish with increasing dose. It was microscopically observed that the increase of conversion was accompanied mainly by the increase of the number of polymer globules below about 30 wt.‐% conversion and by the growth to the larger size of polymer globules formed beyond about 30 wt.‐% conversion.