Suspended Emulsion Copolymerization of Acrylonitrile and Methyl Acrylate

Copolymerization of acrylonitrile and methylacrylate has been carried out using a suspended emulsion process. A water solution containing a water soluble redox system and eventually surfactants, is suspended in a mixture of monomers. The polymerization begins in the water phase, as in emulsion-polymerization, giving rise to small particles, which agglomerate inside the water droplet to form grains, stable after a few percent conversion. The kinetic profile is very peculiar with a rather long induction period followed by moderate acceleration, a step deceleration and finally a very high acceleration due to the activation of occluded radicals when the temperature is rising. The final size of the particles is around 1 micron inside grains of around 100 microns. The morphology of the material can be changed by addition of surfactants. The use of an anionic surfactant (sodium dodecyl sulfate) leads to a rather homogeneous morphology as compared with other cases (no surfactant, cationic or non ionic surfactants).