Silica Particles In Polymer Matrix Research Articles

자외선 경화형 2-EHA/AA 점착제의 점착 물성 및 열 안정성에 미치는 실리카 함량 및 경화제 효과

자외선 경화를 통한 2-EHA/AA 점착제 제조 시 나노 충전제로 실리카를 도입하는 경우 실리카의 표면 처리 여부와 실리카 함량이 점착제의 점착 물성 및 열 안정성에 미치는 영향을 조사하였다. 또한 서로 다른 반복단위 길이를 가진 경화제에 따른 실리카의 보강 효과 차이도 관찰하였다. 실란으로 표면 처리된 실리카의 경우 실리카 표면과 고분자 매트릭스 간 계면 상호 작용으로 고분자 매트릭스 내 분산 정도를 높여 겔 함량의 저하 없이 0.3 wt%의 농도까지 점착 물성을 증가시키는 것으로 확인되었다. 특히 경화제로 PEGDMA를 사용할 때 분자 내 상대적으로 긴 에틸렌옥사이드 반복단위에 기인하는 분자 유연성으로 EGDMA를 사용한 계에 비해 실리카 보강 역할에 더 긍정적인 것으로 나타났다. 또한 열 분해 후 잔존량을 통해 실리카와 고분자 간 강한 계면 결합으로 인한 열 장벽 효과로 점착제의 열 안정성이 향상되는 것을 알 수 있었다. It was investigated that the effect of surface modification and concentration of fumed silica on the adhesion properties and thermal stability of 2-EHA/AA pressure sensitive adhesive (PSAs) prepared by UV irradiation. The influence of repeating units of crosslinking agent on PSAs were also studied. From SEM analysis, PSAs synthesized with surface modified silica had finer dispersion of silica particles in polymer matrix due to the interfacial interaction. Results of the study showed that increase in tack and peel strength when under 0.3 wt% of silane treated silica were added in the reaction mixture. The addition of PEGDMA for crosslinking agent offers positive effect on adhesion properties in comparison with PSAs using EGDMA for crosslinker, which may be attributed to high mobility of ethylene oxide repeating units in PEGDMA. From the thermal degradation residue of PSAs, it was revealed that thermal stability was improved with silica addition due to the strong interfacial bonding between silane modified silica and polymer matrix, which may act as a thermal barriers into 2-EHA/AA PSAs.

Pure and mixed gas CH4 and n-C4H10 permeation in PDMS-fumed silica nanocomposite membranes

Nanocomposite membranes of polydimethylsiloxane (PDMS) with different amounts of fumed silica were synthesized over a porous support of polyacrylonitrile. The prepared membranes were characterized using atomic force microscopy and thermal gravimetric analysis. AFM results indicated the nanoscale dispersion of silica particles in polymer matrix. TGA results indicated that increasing the silica content enhances the thermal stability of membranes. Permeation of methane and n-butane single gases at different upstream pressures and also permeation of a gas mixture containing 3mol% of n-butane in methane were studied and discussed. The results showed that the nanocomposite membrane containing 11wt% of fumed silica exhibited 38% increment in permeability of n-butane and simultaneously 30% increase in selectivity of n-butane over methane. The unusual property enhancement that contradicts to that of conventional filled polymer systems has been discussed based on density of membranes and free volume concept.

Poly(vinyl chloride‐co‐vinyl acetate‐co‐maleic anhydride)/silica nanocomposites derived from in situ suspension polymerization

AbstractPoly(vinyl chloride‐co‐vinyl acetate‐co‐maleic anhydride) (PVVM)/silica nanocomposites were prepared by the suspension radical copolymerization of the monomers in the presence of fumed silica premodified with γ‐methylacryloxypropl trimethoxy siliane. Morphological observation showed that the silica particles of nanometer scale were well dispersed in the copolymer matrix of the nanocomposites films, whereas silica particles tended to agglomerate in the composites films prepared by the solution blending of PVVM with silica. The experimental results show that the thermal stability, glass‐transition temperature, tensile strength, and Young's modulus were significantly enhanced by the incorporation of silica nanoparticles. The enhancement of properties was related to the better dispersion of silica particles in polymer matrix and the interaction between the polymer chains and the surfaces of the silica particles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Effect of Vinyl-Modified Silica and Raw Silica Particles on the Properties of As-Prepared Polymer-Silica Nanocomposite Foams

In this study, the first comparative studies for the effect of vinyl-modified silica (VMS) and raw silica (RS) particles on the physical properties of as-prepared polymer-silica nanocomposite (PSN) foams are presented. First of all, the VMS particles were synthesized by performing conventional acid-catalyzed sol–gel reactions of TEOS in the presence/absence of MSMA molecules. The as-prepared VMS particles were then characterized through Fourier Transform Infrared (FTIR), solid-state 13C-nuclear magnetic resonance (13C-NMR) and 29Si-NMR spectroscopy. Subsequently, a series of PSN materials have been prepared through bulk polymerization of MMA monomers in the presence of VMS and RS particles with BPO as initiator. The dispersion capability of silica particles in polymer matrix was further observed by transmission electron microscopy (TEM) studies. The PSN foams can be further obtained by performing batch-foaming process on as-prepared bulky PSN materials with N2 as foaming agent. The cell structure analysis of the PSN foams was subsequently examined by the scanning electron microscopy (SEM) images. Gel permeation chromatography (GPC) was used to determine the molecular weights of as-prepared samples. It should be noted that the incorporated VMS and RS particles served as heterogeneous nucleation agent in polymer matrix under foaming process to reduce the cell size and increase the cell density of the PSN foams. Furthermore, the VMS particles exhibited a better dispersion capability of silica particles in PMMA matrix as compared to that of RS particles, leading to the PSN foams with smaller cell size and higher cell density. Effect of material composition on the thermal transport properties, thermal stability and mechanical strength of PSN foams were investigated by transient plane source (TPS) technique, thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA), respectively.

Gas permeation properties of ethylene vinyl acetate–silica nanocomposite membranes

The effect of silica nanoparticles on the gas separation properties of ethylene vinyl acetate (EVA) copolymer containing 28% vinyl acetate has been investigated. The EVA and hybrid EVA–silica membranes were prepared via thermal phase inversion method. Silica nanoparticles prepared by hydrolysis of tetraethylorthosilicate (TEOS), through the sol–gel mechanism. The prepared membranes were characterized using FT-IR, SEM, DSC and XRD methods. FT-IR and SEM results indicated the nanoscale dispersion of silica particles in polymer matrix. As confirmed by XRD and DSC analyses, increasing the silica content enhances the amorphous regions significantly. Gas permeation of EVA–silica nanocomposite membranes with silica contents of 5, 6 and 10 wt.% was studied for N 2, O 2, CO 2 and CH 4 single gases at pressures of 4, 6 and 8 bar. The obtained results suggest a significant increase in permeability of all gases and an increase in CO 2/N 2 and CO 2/CH 4 gases selectivities upon increasing the silica content. The possible reasons for such behavior were stated and discussed. The pressure dependence of the gas permeabilities of the membranes was also investigated.

Effects of Mineral Tourmaline Particles on the Photocatalytic Activity of TiO2 Thin Films

In this study, the first comparative studies for the effect of vinyl-modified silica (VMS) and raw silica (RS) particles on the physical properties of as-prepared polymer-silica nanocomposite (PSN) foams are presented. First of all, the VMS particles were synthesized by performing conventional acid-catalyzed sol-gel reactions of TEOS in the presence/absence of MSMA molecules. The as-prepared VMS particles were then characterized through Fourier Transform Infrared (FTIR), solid-state 13C-nuclear magnetic resonance (13C-NMR) and 29Si-NMR spectroscopy. Subsequently, a series of PSN materials have been prepared through bulk polymerization of MMA monomers in the presence of VMS and RS particles with BPO as initiator. The dispersion capability of silica particles in polymer matrix was further observed by transmission electron microscopy (TEM) studies. The PSN foams can be further obtained by performing batch-foaming process on as-prepared bulky PSN materials with N2 as foaming agent. The cell structure analysis of the PSN foams was subsequently examined by the scanning electron microscopy (SEM) images. Gel permeation chromatography (GPC) was used to determine the molecular weights of as-prepared samples. It should be noted that the incorporated VMS and RS particles served as heterogeneous nucleation agent in polymer matrix under foaming process to reduce the cell size and increase the cell density of the PSN foams. Furthermore, the VMS particles exhibited a better dispersion capability of silica particles in PMMA matrix as compared to that of RS particles, leading to the PSN foams with smaller cell size and higher cell density. Effect of material composition on the thermal transport properties, thermal stability and mechanical strength of PSN foams were investigated by transient plane source (TPS) technique, thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA), respectively.

Transparent photo‐curable co‐polyacrylate/silica nanocomposites prepared by sol‐gel process

AbstractThis work prepared the highly transparent photo‐curable co‐polyacrylate/silica nanocomposites by using sol‐gel process. The FTIR and 13C NMR analyses indicated that during the sol‐gel process, the hybrid precursors transform into composites containing nanometer‐scale silica particles and crosslinked esters/anhydrides. Transmission electron microscopy (TEM) revealed that the silica particles within the average size of 11.5 nm uniformly distributed in the nanocomposite specimen containing about 10 wt % of Si. The nanocomposite specimens exhibited satisfactory thermal stability that they had 5% weight loss decomposition temperatures higher than 150°C and coefficient of thermal expansion (CTE) less than 35 ppm/°C. Analysis via derivative thermogravimetry (DTG) indicated that the crosslinked esters/anhydrides might influence the thermal stability of nanocomposite samples. The UV‐visible spectroscopy indicated that the nanocomposite resins possess transmittance higher than 80% in visible light region. Permeability test revealed a higher moisture permeation resistance for nanocomposite samples, which indicated that the implantation of nano‐scale silica particles in polymer matrix forms effective barrier to moisture penetration. Adhesion test of nanocomposite samples on glass substrate showed at least twofold improvement of adhesion strength compared with oligomer. This evidenced that the silica and the hydrophilic segments in nanocomposite resins might form interchains hydrogen bonds with the OH groups on the surface of glass so the substantial enhancement of adhesion strength could be achieved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007