Polymer crosslinking controlled by release of catalyst encapsulated in polycarbonate micro-spheres

EVA crosslinking by ester–silane exchange reaction, controlled by catalyst released from polycarbonate micro-particles, was studied from rheological experiments. Firstly, dibutyltin dilaurate in polycarbonate (PC) (DBTDL) catalyst was encapsulated in polycarbonate micro-particles by an emulsion process. These PC micro-particles have a trimodal size distribution with a mean diameter around 25 μm. Furthermore, scanning electronic microscopy analysis revealed that the DBTDL catalyst is homogeneously dispersed in PC micro-particles. This was verified by DSC experiments which showed a Tg equal to 72 °C for the DBTL micro-particles. Secondly, the deformation and break-up studies of PC micro-particles in molten EVA matrix showed that PC micro-particles can only break up in EVA matrix of high molecular weight (EVA28-03) and for temperatures higher than 200 °C. Thirdly, rheological experiments showed that the crosslink reaction is controlled by the diffusion rate of DBTDL from PC micro-particles. However, this diffusion rate was observed to be independent on either the temperature or the PC micro-particles size.