Keskanok Kawko. A study on silane grafting and water crosslinking of polypropylene and its filled composites . Master's Degree(Polymer Science and Technology). Mahidol University. : Mahidol University, 2004.
A study on silane grafting and water crosslinking of polypropylene and its filled composites
Abstract:
The silane grafting and water crosslinking of polypropylene (PP) and PP composites filled with calcium carbonate were investigated. Vinyltrimethoxysilane (VTMS) was first grafted onto the PP melt in a twin-screw extruder, using dicumyl peroxide (DCP) as an initiator. The grafted samples were subsequently crosslinked in hot water. The effects of grafted formulation, processing conditions and filler addition on the grafting and crosslinking reactions were investigated. The grafting content was determined using FTIR technique, while the degree of chain degradation of PP was examined from the polymer melt flow property. The amount of crosslink as determined by the content gel after solvent extraction was presented. Furthermore, the mechanical and thermal properties of the crosslinked products were also measured.
The results showed that during the grafting reaction of PP, the chain degradation process was accompanied. The competition between the grafting and side process was largely dependent on the process temperature, the amounts of DCP and VTMS, and the presence of filler in the reactions. Increasing the DCP concentration and process temperature, although increasing the grafting degree, resulted in greater degradation of PP. To obtain products with a high degree of grafting without extensive degradation, thease parameters needed to be carefully controlled. The degree of crosslinking was found to depend on the time of the crosslinking process. As the time increased, the amount of gel increased. The silane crosslinked products exhibited better properties than the pure polymer, in terms of tensile strength and modulus, decomposition and heat deflection properties. A synergistic effect of filler addition and silane crosslinking in improving thermal performance of the composites was evident.