Study Of Synthesis Via Concentrated Emulsions And Properties Of Bentonite/Poly (Acrylate) Nanocomposites

In this paper, concentrated emulsion polymerization was developedto prepare bentonite/poly(acrylate) nanocomposites. Which resulted in theformation of nanocomposites with the equilibrium configuration of theplate like morphology of the clay layers in the polymer matrix. The polymeric nanocomposites has fine nanoscale dispersion of thebentonite. Large improvement was shown in the mechanical propertiessuch as toughening efficiency to polyvinyl chloride(PVC) increased, theenhancement of the modulus, stiffness. This material having excellent oil-and heat-resistence has potential applications as material in oil seal, valvestem seal and o-ring of automobile sealing products. The overall preparation for the nanocomposites is divided into twosteps. The first step, bentonite was modified by Hexadecyltrimethylammonium bromide(CTAB) comparing to other ion exchangers. The resultshowed that CTAB had the best result which the basal spacing reached themaximum value. CTAB concentration﹑time and temperature all affectedclay gallery size. iii北 京 化 工 大 学 硕 士 学 位 论 文 The next step, Organo-modified bentonite swelled and dispersed in amixture of MMA,BA and AIBN. Then the mixture was added dropwisewith a syringe to an aqueous solution of SDS and PVA. Until the volumefraction of the dispersed phase became 0.75. After the concentratedemulsion generated, the polymerization was carried under 50℃. The concentrated emulsion polymerization has great advantagesover other methods. Firstly, emulsion particle size range 0.2～100um. Itcan conclude bentonite gallery that is 0.3um for the diameter. Secondly, theorgano-bentonite is limited in monomer droplet that avoid sedimentationand aggregation. Thirdly, the concentrated emulsion polymerization neednot stirring during polymerization. Transmission electron microscope(TEM) showed: in the Bentonite/polymer nanocomposites, the silicate layers were fine dispersed; Thicknessof the stacked silicate layers is 10～100 nm, which consist of about 5～20parallel individual silicate layers; The size of silicate layers have nothing todo with content of the silicate layers in the polymer matrix . Experiments showed the nanocomposites had good oil-resistence. AndPVC modified by nanocomposites obtained excellent flexible effects.