Preparation of water-borne dispersions of polyolefins: new systems for the study of homogeneous nucleation of polymers

Very stable water-borne dispersions of homogeneous ethylene-1-octene (EO) copolymers and of maleic anhydride grafted polypropylene (PP-g-MA) were prepared. A Haake blender was used for dispersing the EO copolymers in water, and for the first time (in case of ‘normal’ molar mass) the use of a non-ionic surfactant turned out to be feasible. A stirred pressure vessel was used for dispersing the PP-g-MA in water beyond its boiling point. Particles having sizes down to submicrometer scale were generated in a controlled way and in large quantities. A study of crystallization of the dispersed particles by DSC reveals a correlation between particle size distribution and crystallization mode. Dispersions of PP-g-MA of sizes from 100 to 200 μm down to sizes below 0.04 μm show heterogeneous, fractionated and homogeneous modes of crystallization and mixtures thereof, respectively, partly under confined conditions. The lowest crystallization peak temperature and the largest extra supercooling ever observed for PP in analogous experiments, 33 and 77 °C, respectively, were realized.