| บทคัดย่อ(English) |
The graft copolymerization of styrene/methyl methacrylate mixturesonto dienebased polymer seed latex has been carried out using cumenehydroperoxide redox initiator. The dienebased polymers were natural rubber,styrene-butadiene rubber and polybutadiene. The experiments were designedusing two fractional factorial design techniques. The monomer conversion,graft copolymer composition and grafting efficiency were determined. Thesynthesized graft copolymers were purified and then characterized by protonnuclear magnetic resonance ('1)H-NMR) analysis and differential scanningcalorimetry (DSC). Transmission electron microscopy (TEM) was used to studythe morphology of the graft copolymers. Grafting efficiency is discussedwith respect to the influence of six process factors and the interaction ofthese factors. The factors studied include the amount of initiator,emulsifier and chain-transfer agent, styrene-to-methyl methacrylate ratio,monomer-to-rubber ratio, and temperature. The analysis of the results fromthe design showed that only the amount of chain transfer agent andtemperature in the range of test had significant effects on graftingefficiency. The mechanism of graft copolymerization has been studied. Itappears that the formation of graft copolymers occurs on the surface of thelatex particles through a chain-transfer process. The graft copolymerproducts could be used as an impact modifier for PVC, thus, blends of thegraft copolymer products and PVC were prepared. Izod impact strength andtensile properties of the graft copolymer products were investigated. |