Free Radical Emulsion Polymerization of Ethylene

Free radical polymerization of ethylene in aqueous media was performed under mild conditions (<i>T</i> < 90 °C and P<sub>ethylene</sub> < 250 bar) using an anionic initiating (ammonium persulfate, APS) and stabilizing (sodium dodecyl sulfate, SDS) system, yielding polyethylene latexes. pH regulation was a key to the feasibility of this process. Particle sizes and morphologies as well as polymerization yields were affected by SDS concentration. In any case, yields increased with polymerization time, especially in the presence of surfactant. When increasing the polymerization pressure, the increase on yields was much stronger in the presence of surfactant and particle sizes increased more when no surfactant was used. Stable polyethylene latexes with relatively high solids content (30%) were synthesized. This article also reports a supercooling effect on the crystallization of the polyethylene particles and evidences promising water-repellency properties of paper coated with the PE latexes synthesized in our laboratory.