Emulsion polymerization of ethylene. II. Effect of recipe on particle size and distribution

Abstract

Particle diameters were measured in electron photomicrographs of polyethylene latexes prepared with a potassium soap, a polyethyoxylated p-alkyl phenol, or a sodium alkyl sulfate. The volume-surface average diameters calculated from these values compare well with those obtained independently by soap adsorption. Plots of the diameters on log probability paper indicate that the diameters follow a log-normal distribution. The width of the distributions is given, and its effect on the difference between the number-average and volume-surface average diameters is discussed. A study of the effect of the recipe shows that the diameter of the average particle produced in the emulsion polymerization of ethylene decreases as the amount of emulsifier is increased, but the addition of tert-butyl alcohol increases particle diameter. Particle diameter is not affected by the initiator within the concentration range normally used. During the course of polymerization, the number of particles slowly increases in the presence of tert-butyl alcohol, but in its absence the number of particles decreases. In the absence of tert-butyl alcohol, the number of particles increases as the 1.1 power of the emulsifier concentration.