| In this paper, based on the principle of molecular design, Poly(methyl methacrylate) grafted silica(PMMA-g-SiO2), poly(styrene-butyl acrylate-acrylic acid) grafted silica(PSBA-g-SiO2) were prepared by emulsion polymerization,γ-glycidoxypropyltrimethoxysilane grafted silica(KH-560-g-SiO2) was also prepared by sol-gel. PVC/PMMA-g-SiO2, PSBA/PSBA-g-SiO2, PMMA/SiO2 and EP/SiO2 composites were prepared via filled polymer matrix with hybrid particles. They were characterized by transmission electron microscope(TEM), dynamic mechanic thermal analyzer(DMA), thermal gravimetric analyzer(TGA), differential scanning calorimeter(DSC), scanning electron microscope(SEM) and rheometer and so on. The mechanisms of organic modified and effects on polymer matrix for hybrid silica particles were studied such as mechanics, thermodynamics, morphology and so on. (1) The monodisperse PMMA-g-silica nano hybrid particles were synthesized by suspension dispersed copolymerization. The nano hybrid particles with a typical core-shell structure and average diameter of 85 nm were filled in PMMA matrix to obtain PMMA/PMMA-g-silica nanocomposites. Compared with the pure PVC, PMMA/PMMA-g-silica nanocomposites had higher mechanical properties, such as when filled 3wt% PMMA-g-silica nano hybrid particles, the tensile strength was up to 54.5 MPa increased 12 MPa, the elongation at break was up to 48.5% increased 27.8%, the impact strength was up to 8 kJ/m2 increased 3.5 kJ/m2, and Rockwell hardness was up to 97 HRB increased 17 HRB. Dynamic storage modulus (E') was increased as well as glass transition temperature(tanδ). The barrier properties of PVC/PMMA-g-SiO2 nanocomposite have been improved. Therefore it is conducive to higher requirements in the packaging industry.(2) The PSBA-g-silica hybrid nanoparticles were synthesized by suspension dispersed copolymerization on the aqueous phase. TEM confirmed the PSBA-g-silica particles were regular spherical structure and its diameter was about 80 nm, organic and inorganic components ratio was nearly 1:1. Water-based PSBA/PSBA-g-silica nanocomposite latex was obtained by filled in PSBA latex with hybrid nanoparticles. The results showed interface adhesive between nanosilica and styrene-acrylic emulsion as well as nanosilica dispersion in styrene-acrylic emulsion has been enhanced at the same time. After filled with a small amount(less than 2.5wt%) of hybrid nanoparticles, the mechanical strength, surface roughness, water resistance, weatherability and other physical and chemical properties of PSBA/PSBA-g-silica nanocomposite were increased significantly especially in the content of 1.5wt%. In addition, the rheological results showed that the hybrid PSBA-g-silica particles can be very good to improve the emulsion stability of the flow and storage.(3) Organic modified silica sol(γ-glycidoxypropyltrimethoxysilane grafted silica) was prepared by sol-gel method. PMMA/SiO2 nano composite was prepared by the solvent blend. TGA showed that the heat resistance of PMMA/SiO2 nanocomposite was improved by organic modified silica. DMA showed that glass transition temperature of PMMA/SiO2 nanocomposite was reduced by organic modified silica. SEM showed that organic modified silica particles in the PMMA matrix had a very good dispersion. Optical and UV analysis showed that the PMMA/SiO2 nanocomposite filled with 33.3wt% organic modified silica particles has excellent optical transparency and UV-shielding ability. In addition, PMMA/SiO2 nanocomposite sol coating on the surface of PVC sheet could reduced surface resistance about 5-6 orders of magnitude. Peel strength of PMMA/silica coatings was 435 gf/15mm. In addition, PMMA/silica coatings had high durability. PMMA/SiO2 nano composite coating was hydrophilic and was conducive to the second coating with water-based latex.(4)Micron and nano size silica particles modified withγ-glycidoxypropyltrimethoxy- silane were prepared by sol-gel method. Epoxy/silica composite was also prepared by the solvent blend. Rheological properties,interfacial bonding properties, curing process, thermal stability, mechanical properties of epoxy/silica composites were studied with the size of silica. Rheological and interface morphology analysis showed the initial steady sate viscosity of epoxy/silica composite was much greater than the net epoxy. Percolation threshold of epoxy filled with nano silica was higher than filled with micron silica. Micron silica in the epoxy matrix had a good dispersion and interfacial bonding strength; moreover nano silica matrix in the epoxy formatted aggregate easily. DSC showed that pre-curing temperature, curing temperature and the reaction activation energy were reduced for epoxy filled with nano silica; on the contrary it had little effect on the curing process for micron silica. TGA showed that epoxy filled with nanosilica had significant heat resistance compared with net epoxy and epoxy/micron silica. DMA showed that storage modulus of epoxy/silica composite was greater than net epoxy, but the glass transition temperature was decreased. It is clear that nano silica can play toughness and strengthen role to epoxy, but only played strengthen role for micron silica. In addition, the content of nano silica in the range of 1-3wt% can be effective to improve bond strength of epoxy/silica. |
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