| Polyvinyl alcohol (PVA) is one kind of commonly usedwater-soluble polymer, as a result of its fine performance and widespreadapplication in industry, its modified work receives the domestic andforeign values day by day, in order to further enhance the performance ofpolyvinyl alcohol, widen its application scope, the predecessors havedone the massive correlative modified work. PVA chemistry modificationmainly uses the chemistry lively of Vinyl acetate's double bond, esterbase and alcoholysis hydroxyl to change the side chain groups orstructure, introduces other monomers to become the copolymer thatprimarily structure by PVA or introduces other functional groups tochange the constitution of PVA macro-molecule.A graft copolymer of AGES-g-PVA was prepared by free radicalpolymerization with sodium 3-(but-3-enyloxy)-2-hydroxypropane-1-sulfonate(AGES) and polyvinyl alcohol (PVA), and with ammoniumpersulfate (APS) as initiator and H2O as solvent. Through the orthogonalexperiment and the single factor experiment, optimized the proportion ofmonomer, reaction temperature, initiator amount and reaction time, anddiscussed the influence factors of the percentage of stem grafting. Withinthe experimental condition scope of research, it was found that thepercentage of stem grafting increases with the increase of initiatorconcentration, AGES dosage, time and temperature.IR, XRD, DTA and TG were used for the confirmation of theformation and thermal stability of AGES-g-PVA, and the reactionmechanism of stem grafting has been extrapolated. The free radical thatproduces by initiator initiates AGES and PVA chain and make thembecome free radical, these two kind of free radical terminated by thecoupling reaction and realizes stem grafting AGES to the PVA chain.Because the energy of C-H bond on the PVA main chain that link thehydroxyl is smaller than the others on the PVA main chain, therefore theC-H bond that has this property is easier to form the active spot and the stem grafting is easier to carry on, stem grafting AGES to PVA mainchain also mainly react in these position.Through the water-soluble test of AGES-g-PVA, it was found thatgrafting AGES to PVA can obviously improve the dissolved performanceof PVA. Increases with the dosage of initiator and AGES, the modifiedproduct dissolve temperature assumes the tendency which falls at firstand rises at last. Extrapolated its reason, possibly is because in thereaction process, simultaneously have reaction of stem grafting AGES toPVA and reaction of PVA intermolecular cross link, to AGES-g-PVAwater-solubility, they are competition relationship. AGES besides playsthe role of improves PVA water-solubility, but also had the part to becross linker, urged PVA intermolecular partial junctions association,enhanced the cross link degree of PVA, reduced the helpful function ofAGES to water-solubility of PVA.It was found that partial products of grafting are gelatinous and can'tdissolve in the water, furthermore, their water-absorption capability arerelative high. This phenomenon showed well that the reaction of graftingand cross link are coexists in this experimental process, simultaneously italso confirmed the reaction mechanism from the other aspect.The thermal stability of all AGES-g-PVA is better than PVA, and themelting temperature are lower. Through the contrast experiment, it wasfound that the reaction temperature and AGES dosage are primaryinfluence factor of thermalproperties of product. Reduces the reactiontemperature and increases the AGES dosage could enhance the thermalstability of modified product, the change of initiator dosage has littleinfluence to the thermal stability. |
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