Radiation‐induced heterogeneous polymerization of ethylene in the presence of ethyl alcohol

The radiation‐induced heterogeneous polymerization of ethylene in ethyl alcohol was carried out in a reactor with a capacity of 100 ml under the following reaction conditions: temperature, 24 ± 3°C; pressure, 200–400 kg/cm2; amount of ethyl alcohol, 30–70 ml; dose rate, 3.7 × 104−1.05 × 105 rad hr. The effects of amount of ethyl alcohol, pressure, and dose rate on the rate of polymerization at the steady state, the amount of polymerized monomer, the molecular weight of polymer, and the number of polymer chains were studied compared with the results obtained in the polymerization in tert‐butyl alcohol. It was found that there is an acceleration period in the early stage of reaction followed by a steady state. The rate of polymerization was maximum when about 50 ml of ethyl alcohol was used. The molecular weight of polymer increased with a decrease in the amount of ethyl alcohol. The dependences of pressure (p) and dose rate (I) on the rate of polymerization at steady state (Rs) and the molecular weight of polymer (M̄n) were expressed as follows; Rs ∝ p0.74, M̄n ∝ p0.3−0.4, Rs ∝ I0.9 and M̄n ∝ I−0.1 −0.0. The results were analyzed by a kinetic treatment based on a reaction mechanism containing both first‐and second‐order terminations. The rate constant of first‐order termination by radical occlusion was considerably larger than that in the polymerization in tert‐butyl alcohol, because the affinity of ethyl alcohol for polyethylene is smaller than that of tert‐butyl alcohol. It was found that chain transfer to ethyl alcohol takes place easily and the G value of ethyl alcohol for initiation is larger than 1.5.