| Polyvinyl chloride (PVC) paste resin is a kind of PVC resin, which is usually applied in the plastisol form. Microsuspension polymerization (MSP) is always used to prepare PVC paste resin, in which PVC latex particles formed in a different way from conventional emulsion polymerization. The particle size (PS) and particle size distribution (PSD) of PVC latex prepared by MSP are influenced by the type, ratio and usage of emulsifier/costabilizer, swelling and homogenization process, et al., and further affected the rheological property of PVC plastisol. In this thesis, the swelling and particles formation process of VC MSP, the relationships between polymerization conditions-PS and PSD of latex particles-rheologteal properties of PVC plastisol, and VC single electron transfer living polymerization in microsuspension system were investigated.Firstly, the formation of sodium dodecyl sulfate (SDS)/cetyl alcohol (CA) complex micelles and swelling of trichloroethyl (used as the model compound of vinyl chloride) into complex micelles to form monomer micro-droplets were studied. It was found that the formation of complex micelles and micro-droplets were both thermodynamically driven process, and the swollen monomer was increased as swelling time increased or high speed shear dispersion applied. The complex micelles exhibited super-swelling capacity to monomer. The comparison on the kinetics of VC MSP, suspension and emulsion polymerizations showed that VC MSP exhibited a greater polymerization rate than suspension polymerization, but lower than emulsion polymerization at the same initiation conditions. The above kinetics differences were attributed to the different partition of primary free-radicals in water/micelles/monomer micro-droplets and the different nucleation modes.Secondly, the effect of initiator type, homogenization processes, ratio of oil/water, amount of CA and ratio of SDS/CA on the PS and PSD of PVC latexes were investigated. It was found that PVC latex prepared by MSP using APS as the initiator contained a greater number particles with size lower than 100nm, while no more PVC particles with size lower than 100nm was appeared in PVC latex prepared by MSP using ABVN as the initiator. Either prolonging the swelling time or applying high rate shear could enhance homogenization performance, resulting in the decreases of PS and PSD. Sufficient CA was needed to keep the stability of MSP system, and PS and PSD were decreased as CA usage increased. Keeping SDS/CA ratio constant, PS was firstly increased and then decreased as the total usage of SDS and CA increased.Thirdly, the rheological behavior of PVC plastisol was tested by rheometer. Plastisols prepared by using PVC resin obtained in swelling MSP acted as Newtonian fluid, and then dilatant fluid as shear rate increased, while plastisol prepared by using PVC resin obtained in homogenized MSP showed pseudoplastic to a large extent and lower viscosity. The plastisols paste prepared from MSP PVC using APS as the initiator showed pseduoplastic behavior and greater apparent viscosity, while the plasticized paste prepared from MSP PVC using ABVN as the initiator showed dilatant behavior. The viscosity of plastisol was increased as the amount of CA using in MSP increased.Finally, VC single electron transfer living radical polymerization in the microsuspension system was tested. It was found that the polymerization was hardly proceeded when SDS was used as the main emulsifier, while the polymerization rate was obviously increased when CTAB was used as the main emulsifier. SET-DT MSP using CTAB/CA emulsification system exhibited a greater rate than suspension polymerization at the same initiator/catalyst system, and showed living nature. However, the latex stability was low when CTAB was used as the main emulsifier. |
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