KINETICS OF SILANE GRAFTING AND MOISTURE CROSS-LINKING OF POLYETHYLENE AND ETHYLENE PROPYLENE RUBBER

Peroxide initiated graft copolymerization of vinyl trimethoxy silane (VTMO) and vinyl triethoxy silane (VTEO) onto polyethylene (PE) and ethylene propylene copolymer (EPR) was studied. The kinetics of grafting, studied by differential scanning calorimetry, are the same for all the systems and the activation energy for VTMO is 170 +/- 4 KJ / mol. Activation energy for VTEO is 185 +/- 5 KJ / mol. The VTMO and VTEO graft copolymers of PE and EPR were prepared by reactive processing in a Brabender extruder in the temperature range of 150-200-degrees-C. Moisture catalyzed crosslinking of the silane grafted copolymer was also studied. The influence of the structure of the catalyst, its concentration, moisture concentration, temperature, and time on degree and rate of crosslinking has been evaluated. Crosslinking reactions follow first order kinetics with respect to both catalyst and moisture concentration. Activation energy (E(a)) of the crosslinking reaction has been determined as 65 KJ mol-1. The mechanism of grafting and crosslinking is discussed.