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1.
Effects of preparation methods on the property of PMMA/SBA-15 mesoporous silica composites 总被引:2,自引:0,他引:2
In the paper, poly(methyl methacrylate)(PMMA)/SBA-15 composite materials were prepared by four different methods, that is,
in-situ batch emulsion polymerization in the presence of mesoporous SBA-15, PMMA emulsion mixed with SBA-15 powder or dispersion
in water, PMMA powder mixed with SBA-15 powder, and the properties of the composite materials were determined and compared.
The composites were characterized by infrared spectroscopy (IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA),
differential scanning calorimetry (DSC), dynamic mechanics analysis (DMA) and scanning electron microscope (SEM). The results
showed that the glass transition temperatures (Tg), the storage modulus and tensile strength of the PMMA/SBA-15 composites
were all improved obviously, while the thermal decomposition temperature did not influenced apparently. The composite made
by in-situ batch polymerization exhibited the most improvement in the mechanical properties and Tg while the composite prepared
by mixing PMMA emulsion and SBA-15 dispersion gave rise to the least improvement in the mechanical properties and Tg. These
results were contributed to introducing different amount of voids into polymer matrix which were demonstrated by dielectric
constant measurement and SEM morphology observation. 相似文献
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An ordered mesoporous material, such as SBA-15 was considered as a promising reinforcement agent for polymeric materials due to its large surface area and uniform pore structure. In this paper, poly(methyl methacrylate) (PMMA)/SBA-15 composites were prepared by in situ free-radical solution polymerization of MMA in the presence of SBA-15. The effects of SBA-15 content on solution polymerization and the properties of the final polymer composite were investigated. The PMMA molecular weight and its distribution in PMMA/SBA-15 composites were determined by gel permeation chromatography. Fourier-transform infrared spectra, X-ray diffraction, thermal gravimetric analysis (TGA), differential scanning calorimeter and dynamic mechanical analysis were used to characterize the structure and properties of the composites. The morphology of the composites was observed by scanning electric microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the monomer conversion dropped off, but the polymer average molecular weight increased upon the introduction of SBA-15 into solution polymerization process. When compared with pure PMMA, the storage modulus of the composites was improved and the highest improvement was acquired at 1 wt% of SBA-15, based on the monomer feed content. The glass transition temperatures of the composites were increased slightly. TGA results confirmed that the thermal stability of the composite was not influenced much and a higher degree of terminal vinyl groups was formed in the product of polymerization. SEM and TEM images indicated that SBA-15 particles were incorporated into the polymer matrix. 相似文献
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Silver nanoparticles were prepared by removing silica from mesoporous Ag/SBA-15 composites. The results of nitrogen adsorption–desorption isotherms, X-ray diffraction, transmission electron microscopy and UV–vis spectroscopy indicated that Ag nanoparticles existed in the pore channels of SBA-15. Ag nanoparticles with diameters in the range of 2.5–5.5 nm and a narrow size distribution were confirmed by atomic force microscope images and energy-dispersive X-ray spectroscopy. UV–vis spectroscopy showed a broad emission peak of Ag nanoparticles centered at ca. 438 nm. 相似文献
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Chunguang Gao Tieming Zhang Pengfei Gao Yongxiang Zhao 《Journal of Porous Materials》2013,20(1):47-53
Bridged-ferrocene functionalized mesoporous SBA-15 (Fc-SBA) were prepared by evaporation-induced self-assembly (EISA) of 1,1′-bis[(2-(triethoxylsilyl)ethyl)ferrocene and tetraethyl orthosilicate with polymer Pluronic P123 as a template under acid conditions. The prepared materials were characterized by N2 sorption, XRD and TEM, and the results showed the materials exhibited highly ordered 2D hexagonal pore structure, thick pore wall with the pore width of 4.66–6.58 nm. The highly ordered structure maintained even the content of the ferrocene precursor in the initial mixture is 30 mol%. The FT-IR revealed that the ferrocene bridge is preserved during the material synthesis and subsequent extraction procedure. In the reaction of phenol hydroxylation, the phenol conversion was found to be almost the same as the homogeneous ferrocene catalyst over the Fc-SBA mesoporous materials. The selectivities of catechol and hydroquinone were about 55 and 40% respectively. 相似文献
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《Ceramics International》2021,47(23):33002-33009
To simplify the treatment of radioactive wastewater and reduce the secondary pollution, in this work, mesoporous ZrO2/SBA-15 was synthesized and employed for the first time as both the adsorbents and crystalline matrices for efficient enrichment and in-situ immobilization of U in radioactive wastewater. In general, U was efficiently enriched by using the mesoporous ZrO2/SBA-15 and then immobilized into ZrSiO4 ceramics by the followed sintering process. The U-adsorbed ZrO2/SBA-15 was changed to stable ZrSiO4–U ceramics by sintering at 1250–1450 °C for 6 h. The results also provided the evidence that both U(Ⅳ) and (Ⅵ) were incorporated into the crystal structure of ZrSiO4 by replacing Zr(Ⅳ). Furthermore, all the obtained ZrSiO4–U ceramics exhibited good aqueous durability. Given the high adsorption capacity and good aqueous durability, it is expected that the ZrO2/SBA-15 is attractive for actual applications in treatment of U containing radioactive wastewater. 相似文献
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Fa‐Ai Zhang Ming Luo Zheng‐Ji Chen Zhi‐Bo Wei Thomas J. Pinnavaia 《Polymer Engineering and Science》2014,54(12):2746-2752
Rod‐like and spherical mesoporous SBA‐15 silica particles were synthesized as pure silicas and surface modified by organosilane coupling agents firstly, and then the effects of these mesoporous materials on the critical micelle concentration (CMC) of sodium dodecylsulfate (SDS), the stabilities of batch and semi‐continuous MMA emulsion polymerizations, and the molecular weights and molecular weight distributions of the polymer products were studied. The incorporation of both unmodified and silane‐modified forms of the mesoporous silica particles in the polymerization reaction increased the CMC of SDS. The presence of the unmodified mesoporous silica in the polymerization process led to instability in the batch emulsion polymerization process, as indicated by the formation of increased amounts of coagulum, and a decrease in the molecular weight of the polymer product. However, in comparison to the polymer formed in the absence of particle additives the molecular weight of the PMMA polymer increased with the amount of emulsifier and the addition of silane‐modified SBA‐15 particles, suggesting the growth of the polymer chains is facilitated at least in part by reaction in the pores of the particles. The improvement in molecular weight indicates that semi‐continuous MMA emulsion polymerization is best suited for the preparation of PMMA–mesoporous silica composites. POLYM. ENG. SCI., 54:2746–2752, 2014. © 2013 Society of Plastics Engineers 相似文献
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Sakthivel Gandhi Kavitha Thandavan Swaminathan Sethuraman Uma Maheswari Krishnan 《Journal of Porous Materials》2013,20(5):1009-1015
Mesoporous silica (SBA-15) and iron oxide incorporated silica (Fe2O3-SBA-15) were synthesized by co-operative self-assembly technique. Samples were characterized using nitrogen adsorption–desorption isotherm, electron microscopic and spectroscopic techniques. The results confirm the uniform distribution of pores, presence of metal oxides in the pores as well as in the surface of the mesoporous wall and oxidation state of iron in the Fe2O3-SBA-15. The photocatalytic degradation of methylene blue (MB), sulphorhodamine B (SR-B) and methyl orange (MO) by Fe2O3-SBA-15 was investigated. It was observed that Fe2O3-SBA-15 degraded 98 % of MB, 96 % of SR-B and 99 % of MO within 3 h after exposure to sunlight. SBA-15 does not exhibit any photocatalytic effect. These results demonstrate the potential of Fe2O3-SBA-15 for environmental pollution control. 相似文献
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Aqueous core polystyrene microspheres fabricated via suspension polymerization basing on a multiple pickering emulsion 下载免费PDF全文
Multi‐hollow or hollow polymer particles are of great interest in many fields. Here we successfully fabricate polystyrene microspheres with aqueous cores through w/o/w Pickering emulsion stabilized by modified SiO2 nanoparticles. The final structure and constituents of the microspheres is investigated via SEM, X‐ray photoelectron spectra, and thermo‐gravimetric analysis. The results demonstrate that the size and amount of aqueous cores in the microspheres can be tuned by the original structure of the multiple emulsions: when the volume fraction of inner water is 0.2, the inner structure of the microspheres obtained is porous and each pore is not interconnected; when the volume fraction of inner water is increased to 0.7, the resulting products are hollow microspheres and when 0.3% wt/vol of salt is added to the inner aqueous phase, the inner pores of the resulting microspheres enlarge or even coalesce. The multi‐hollow or hollow polystyrene microspheres with aqueous cores are expected to be candidates for encapsulation in biotechnology. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39761. 相似文献
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Svatopluk Chytil Lise Haugland Edd A. Blekkan 《Microporous and mesoporous materials》2008,111(1-3):134-142
Mesoporous silica SBA-15 was synthesised at 80 °C. The calcined solids were exposed to a unilateral external pressure in the range 16–191 MPa in order to monitor the impact of the mechanical pressure on the properties of SBA-15. N2 adsorption–desorption measurements, XRD and UV-Raman spectroscopy was used in order to evaluate the changes occurring in the SBA-15. For the XRD measurement, an internal Si standard was used to correct the position of the SBA-15 patterns. It appeared that the elevated pressure has no influence on the hexagonal cell parameter a. Through the N2 sorption measurements the fraction of the preserved mesoporous structure was estimated to be 60% when the highest pressure has been used. As the remaining part of the material is irreversibly disintegrated into small particles, the pressed sample is considered to be heterogeneous. However, the preserved fraction is slightly modified, showing a smaller pore width and plugs located within the mesopores. The plugs most likely originate from a disintegrated fraction of the SBA-15. UV-Raman spectroscopy shows that the relative intensity of the band associated with the siliceous network (ω1) has decreased on the pressed samples resulting in a less ordered material possessing an enhanced population of silanols as compared to parent SBA-15. We propose that the disorder introduced by pressing is responsible for the observed expansion of the SBA-15 walls, which is detected for the samples treated at higher pressures (112, 191 MPa). 相似文献
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Polymer/carbon nanotube (CNT) composites were synthesized by first attaching functional groups onto CNT to make them reactive. For this purpose, we developed a combined approach of non-covalent and covalent functionalization process. Covalent functionalization was accomplished through refluxing of CNT with mineral acid (HNO3) and with oleic acid. The FTIR spectra and zeta-potential data confirmed the effectiveness of functionalization and the improved dispersibility of the functionalized CNT. Styrene was used to synthesize polystyrene (PS)/CNT composites in conjunction with emulsion polymerization, a versatile and industrially important method that is seldom reported for composite synthesis. Our PS/CNT composites had high monomer conversion and the measured thermal and mechanical properties showed significant improvements over pure PS even with modest CNT content. 相似文献
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Chemical modification (CM) and deposition-precipitation (DP) methods were used for the dispersion of active Au nanoparticles on mesoporous silica materials in this work. XRD, TEM, N2 adsorption isotherms and UV-Vis absorption spectra were used to characterize in detail Au-SBA-15 materials prepared by the two methods. The analysis results showed that high loading (1.7%, by mass) and uniform Au nanoparticles (approximately 3 nm) were dispersed in the channels of mesoporous SBA-15 by the CM method. While for the DP method, most of Au nanoparticles with the size of 10—15nm were aggregated outside of the channels of SBA-15 and the actual loading of Au was only 0.38% (by mass). 相似文献
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Rubber–styrene solutions of various compositions and containing a suitable initiator have been polymerized starting from concentrated emulsions in which the above solutions constitute the dispersed phase and solutions of sodium dodecylsulfate in water the continuous phase. Latexes of rubber-modified polystyrene composites have been thus obtained. Solutions of rubber–styrene have been also polymerized by bulk polymerization for comparison purposes. The molecular weights have been determined from intrinsic viscosity measurements, and the mechanical properties of the composites have been studied via tensile testings. Because of the lower mobility of the high-molecular radicals in the concentrated emulsions, higher molecular weights have been obtained by the concentrated emulsion polymerization than by the bulk polymerization method. The tensile properties and toughness of the composites have been determined. While the two polymerization methods provide high, comparable toughness, the concentrated emulsion method generates latexes that can be easily processed in any desirable shape. © 1994 John Wiley & Sons, Inc. 相似文献
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Mesoporous materials (2–50 nm) have generated much interest due to its multi-faceted applications as catalysts, adsorbents
and drug delivery systems. This study is the first of its kind to systematically investigate the effect of polyhydric solvents
on the morphology, catalytic and adsorption properties of self-oriented mesoporous silica. Three different mesoporous SBA-15
silica materials were synthesized using Water (SW), Glycerol (SG) and Ethylene Glycol (SEG) as solvent. They were characterized
using FE-SEM, HR-TEM, small angle XRD, FT-IR, BET and solid state NMR. Morphological studies such as pore characteristics,
surface area and the functionalization were carried out by comparing their catalytic and adsorption properties. Each mesoporous
sample was used to catalyze biodegradable aliphatic polyester synthesis namely poly (butylene succinate), poly (butylene pimelate)
and poly (butylene sebacate) and compared with a conventional homogeneous catalyst SnCl2·2H2O. The results offered higher purity and yield of polyesters and they took the order as SW > SG > SEG. The adsorption efficiency
of each mesoporous sample was compared using the fluorescent dye Rhodamine-B and it took a reverse order (SEG > SG > SW) to
that of the catalytic efficiency. This difference may be attributed to the difference in free active sites, ordered morphology
of pores and surface area. The synthesized polyesters were characterized using FT-IR, 1H NMR, XRD, GPC, DSC and the adsorption studies, using UV–Visible spectrophotometer. 相似文献
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Nanoparticles of polypyrrole (PPy) in 40/60 wt % natural rubber (NR)–polystyrene (PS) blends were synthesized by emulsion polymerization using ferric sulfate [Fe2 (SO4)3], sodium dodecyl sulfate (SDS), and n‐amyl alcohol as the oxidant, surfactant, and cosurfactant, respectively. The NR/PS/PPy blends were characterized by Fourier transform infrared spectroscopy (FTIR), elemental analysis, thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM). FESEM micrographs showed that NR/PS/PPy blends were homogeneous, and PPy nanoparticles were well distributed throughout the binary matrix of NR/PS. The size of PPy particles in the blends was in the range of 26–80 nm. The electrical conductivities of the pellets prepared from NR/PS/PPy blends increased as the composition of PPy nanoparticles was increased, which were in the range of 8.9 × 10?8 – 2.89 × 10?4 S/cm. Thermal stability of the blends increased as the content of PPy was increased, as shown by TGA thermograms. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献