Biogas can be used as an alternative energy source for producing heat and electricity;however, volatile methylsiloxanes(VOSiC) present in biogas can severely damage heat exchangers, turbines and gas engines. Consequen...Biogas can be used as an alternative energy source for producing heat and electricity;however, volatile methylsiloxanes(VOSiC) present in biogas can severely damage heat exchangers, turbines and gas engines. Consequently, e cient removal of VOSiC from biogas that is used as a biofuel is required. In this work, acetylated silica gel(Ac@SG) was synthesized,via treatment of microporous silica gel(SG) with acetic anhydride as an adsorbent, for removal of VOSiC from biogas,and characterized with XRD, SEM–EDS, N2-BET and FT-IR. This Ac@SG adsorbent exhibited a meso-/microporous structure and hydrophobic surface, indicating it was a more e cient adsorbent for removing hexamethyldisiloxane(L2) and octamethylcyclotetrasiloxane(D4) from biogas samples than conventional SG. It was found that the adsorption capacities of Ac@SG reached 304 mg L2/g for hexamethyldisiloxane and 916 mg D4/g for octamethylcyclotetrasiloxane at lower temperatures in the experimental range, and water had no significant e ect on its absorption e ciency. The used Ac@SG could be easily regenerated by heating it at 110 °C, and the adsorption capacity of recycled Ac@SG for hexamethyldisiloxane and octamethylcyclotetrasiloxane was kept constant in four recycle adsorption experiments.展开更多
The reactive diluent prepared by siloxane modified Trimethylene oxide can improve the performance of the UV curing system.Therefore,1,7-bis[(3-ethyl-3-methoxyoxacylobutane)propyl]octadecylosiloxane(BEMOPOMTS)was synth...The reactive diluent prepared by siloxane modified Trimethylene oxide can improve the performance of the UV curing system.Therefore,1,7-bis[(3-ethyl-3-methoxyoxacylobutane)propyl]octadecylosiloxane(BEMOPOMTS)was synthesized from diethyl carbonate,trimethylopropanes,allyl bromide,and 1,1,3,3,5,5,7,7-octadecylosiloxane as the main raw materials.BEMOPOMTS can be used as reactive diluents in the field of cationic UV curing.It has good thermal stability,and the addition of BEMOPOMTS significantly improves the tensile strength and elongation at break of epoxy resin.Compared with the pure epoxy resin,adding 20%BEMOPOMTS increased the elastic modulus by 25%to 677 MPa.展开更多
Landfill biogas is a potential alternative for fossil fuel,but the containing impurities,volatile methyl siloxanes(simplified as siloxanes),often cause serious problems in gas turbines when applied to generate electri...Landfill biogas is a potential alternative for fossil fuel,but the containing impurities,volatile methyl siloxanes(simplified as siloxanes),often cause serious problems in gas turbines when applied to generate electricity.In this research,a collecting and analyzing method based on solvent adsorption and purge and trap-gas chromatography-mass spectrometry was established to determine the siloxanes in biogas from a landfill in Jinan,China,and adjacent ambient samples,such as soil,air,and leachate of the landfill.The results showed that,octamethylcyclotetrasiloxane(D4)and decamethylcyclopentasiloxane(D5)accounted for 63%of total siloxanes;and without considering D4 and D5,the order of detected siloxanes in concentration was found relating to Gibbs free energies of molecules,namely that higher abundant siloxane(except for D4 and D5)usually had lower Gibbs free energy.Additionally,the mass ratio between D4 and octamethyltrisiloxane(L3)in the bio gas varied with different garbage age in landfills,possibly revealing the breaking-down of larger siloxane molecules with time.The samples,which were collected from environmental samples adjacent to the landfill,such as soil,water,and air,presented much higher siloxane level than urban or rural area away from landfills.The current H2 S scrubber of the landfill biogas could decrease the total siloxanes from 10.7 to 5.75 mg/m^3 due to Fe2 O3 and a refrigerant drier in a purification system and cyclic siloxanes were more easily removed than linear ones.展开更多
Siliconated polyurethane (Si-PU) was synthesized using isophorone diisocyanate (IPDI), hydroxybutyl-terminated polydimethylsiloxane (PDMS), polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG),...Siliconated polyurethane (Si-PU) was synthesized using isophorone diisocyanate (IPDI), hydroxybutyl-terminated polydimethylsiloxane (PDMS), polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), 1,6-hexanediol (HDO), dimethylol propionic acid (DMPA) and triethylamine (TEA). Based on butyl acrylate (BA), 2, 2, 2-trifluoroethylmethacrylate (TFEMA) and Si-PU as a seed emulsion, a novel core-shell type acrylic-polyurethane hybrid emulsion, containing siloxane and fluorine (F-Si-PU), was prepared by seeded emulsion polymerization. The contents of siloxane and fluorine were determined according to the feed ratio. Fourier transform infrared spectroscopy (FTIR) was used to identify the chain structures of Si-PU and F-Si-PU. Investigation of transmission electron microscopy (TEM) confirmed the core-shell structure of F-Si-PU emulsion. Measurement results of water contact angle and the swelling ratio in water and n-octane for cured film showed that the water and the oil resistances for F-Si-PU had been significantly improved at a suitable content of fluorine and siloxane.展开更多
In order to inhibit and remove the thin ice and extend the lifetime of the damaged bridge, the self-healing mechanism and hydrophobic performance of asphalt modified by siloxane and polyurethane (ASP) were studied by ...In order to inhibit and remove the thin ice and extend the lifetime of the damaged bridge, the self-healing mechanism and hydrophobic performance of asphalt modified by siloxane and polyurethane (ASP) were studied by dynamic shear rheology (DSR), fluorescence microscope (FM), atomic force microscope (AFM), the fracture-healing-re-fracture test and molecular simulations. The experimental results indicated that the selfhealing capability of ASP increased with increasing heating time and temperature. Furthermore, the addition of siloxane could improve the reaction energy barrier and complex modulus, and it is believed that the self-healing is a viscosity driven process, consisting of two parts namely crack closure and properties recovery. Contact angle of ASP increased with the increasing siloxane content and it deduced that the siloxane could improve the hydrophobic performance of ASP and the ASP molecule model could simulate well the self-healing mechanism and hydrophobic performance of ASP.展开更多
Poly[(methylsilylene ethynylene phenylene ethynylene)-co-(tetramethyldisiloxane ethynylene phenylene ethynylene)]was synthesized by polycondensation reaction of m-diethynylbenzene magnesium reagent with 1,3-dichlorote...Poly[(methylsilylene ethynylene phenylene ethynylene)-co-(tetramethyldisiloxane ethynylene phenylene ethynylene)]was synthesized by polycondensation reaction of m-diethynylbenzene magnesium reagent with 1,3-dichlorotetramethyldisiloxane and dichloromethylsilane.The copolymer was characterized by FT-IR,~1H NMR,differential scanning calorimetry and thermogravimetric analysis.The results show that the copolymer exhibits good processability and cures at low temperatures.The cured copolymer shows high thermal stability.展开更多
Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynami...Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynamic mechanical property analysis. The results showedthat the introduction of chloromethyl group into polysiloxane increased its polarity and henceimproved the miscibilities with polytetramethylene oxide and polyurethane hard segment.Particularly, in the case of N-methyldiethanolamine extended materials, the surface and tensileproperties of these samples can be adjusted by various ratios of two soft segments.展开更多
Porous and bioactive gentamicin sulfate-loaded gelatin-siloxane hybrids were successfidly synthesized by using a combined sol-gel processing, post-gelation soaking, and freeze-drying process. A bone-like apatite layer...Porous and bioactive gentamicin sulfate-loaded gelatin-siloxane hybrids were successfidly synthesized by using a combined sol-gel processing, post-gelation soaking, and freeze-drying process. A bone-like apatite layer was able to form in the Ca^2+-containing porous gentamicin-loaded hybrids upon soaking in a simu- lazed body fluid (SBF) up to 1 day. The drug release of gentamicin sulfate was with a burst, followed by an almost constant release up to 7 days. And the rate of release in acidic medium was lower than that in the neutral and basic media.展开更多
A hybrimer based on epoxy resin and phenyl-siloxane was prepared by polymerization and a solgel condensation reaction in which Eporite-904 (807 g/eq) bisphenol-A-type epoxy resin, 3-isocyanatopropyltriethoxysilane (IP...A hybrimer based on epoxy resin and phenyl-siloxane was prepared by polymerization and a solgel condensation reaction in which Eporite-904 (807 g/eq) bisphenol-A-type epoxy resin, 3-isocyanatopropyltriethoxysilane (IPTES) and phenyltriethoxysilane (PTEOS) acted as precursors. The thermal and optical properties of the epoxy/siloxane hybrimer were studied. The thermogravimetric analysis (TGA) results implied that the hybrimer could increase the crosslink density and enhance the thermal properties. The optical properties were measured after thermal and UV aging. The refractive indexes of the epoxy/siloxane hybrimers were 1.66 - 1.70, and the transmittances of the cured hybrimers were above 90% in the visible wavelength. After a 120°C/24-h thermal aging test, the decreases in the refractive index and transmittance were less than 5% and 20% respectively. The epoxy/siloxane hybrimers also showed low discoloration upon thermal aging at 120°C for 24 h under an air atmosphere.展开更多
A homogeneous longtime stabilized transparent nanometer TiO2 organic solution was obtained by means of the simultaneous hydrolysis and co-polycodensation of tetrabutyltitanate (TBT) and methacryloxypropyltrimethoxysil...A homogeneous longtime stabilized transparent nanometer TiO2 organic solution was obtained by means of the simultaneous hydrolysis and co-polycodensation of tetrabutyltitanate (TBT) and methacryloxypropyltrimethoxysilane (MAPTMS) by the sol-gel process. The particle size of nanometer titanium dioxide was controlled by use of bifunctional silanes, such as diphenyldimethoxysilane (DPDMS), diphenyldiethoxysilane (DPDES) and dimethyldiethoxysilane (DMDES). The effect of TiO2 content in the solution on the refractive index of system was discussed in detail. The result shows that the refractive index of solution increases linearly with TiO2 content. The refractive index of the three hybrid nanometer materials attained 1.6053, 1.5846 and 1.5346, respectively. The size of nanometer particles was characterized by TEM and the particle diameter thus obtained is in the range of 20-90 nm. FT-IR spectra of the materials show that the Ti— O—Si bond is formed.展开更多
Poly(methyl methacrylate) (PMMA) was used to wrap alumina siloxane sol through emulsion polymerization. A kind of suspensions with notable ER effect was produced by fully mixing the prepared microcapsule with silicon...Poly(methyl methacrylate) (PMMA) was used to wrap alumina siloxane sol through emulsion polymerization. A kind of suspensions with notable ER effect was produced by fully mixing the prepared microcapsule with silicon oil. Meanwhile a series of PMMA wrapped alumina-siloxane gel doped with rare earths was obtained and its ER effect was tested, like viscosity of different rare earth ion doped samples in different powder concentrations and at different temperatures, at the same time, leak current density and dielectric constant were measured. Results show that the ER effect of this suspension is remarkable, and its stability is much better. The condition of emulsion polymerization and the mechanism of effect are discussed.展开更多
A compound,3-ethyl-3-hydroxymethyloxetane(EHO),was synthesized with diethyl carbonate and trihydroxypropane as raw materials,3-ethyl-3-allylmethoxy oxetane(EAMO)was synthesized with EHO and allyl bromide,and 1,1,3,3,5...A compound,3-ethyl-3-hydroxymethyloxetane(EHO),was synthesized with diethyl carbonate and trihydroxypropane as raw materials,3-ethyl-3-allylmethoxy oxetane(EAMO)was synthesized with EHO and allyl bromide,and 1,1,3,3,5,5-hexamethyl-1,5-bis[(3-ethyl-3-methoxyoxetane)propyl]trisiloxane(HMBEMOPTS)was synthesized with EAMO and 1,1,3,3,5,5-hexamethyltrisiloxane(HMTS).HMBEMOPTS is a novel UV-curable oligomer.The test of photo-DSC shows the photosensitivity of HMBEMOPTS is better than the ordinary oxetane,3-ethyl-3-[(3-ethyloxetan-3-yl)methoxymethyl]oxetane.HMBEMOPTS was mixed with bisphenol A type epoxy resin E-51 to prepare a cationic UV-curable system,and triarylsulfonium hexafluoroantimonate(UV-6976)was used as a cationic photoinitiator.The mechanical tests of coating films prove that when the mass fraction of HMBEMOPTS is 50%,the mechanical properties of the curing system are the best.The impact strength of the UV-curable films is measured to be 40 kg·cm and the flexibility is 2 mm;the tensile strength and flexural strength of the prepared specimens are 20.74 MPa and 13.43 MPa,respectively.The experimental results show that HMBEMOPTS can effectively improve photosensitivity and flexibility of the photosensitive resin.展开更多
PMMA wrapped alumina siloxane gel was obtained by using poly (methyl methacrylate) (PMMA) to wrap alumina siloxane sol which was made from water glass, aluminum nitrate and α methacrylic acid. Meanwhile, rare eart...PMMA wrapped alumina siloxane gel was obtained by using poly (methyl methacrylate) (PMMA) to wrap alumina siloxane sol which was made from water glass, aluminum nitrate and α methacrylic acid. Meanwhile, rare earth ions were used to dope in the course of reaction, and stable suspensions was produced by putting PMMA wrapped microcapsule powder doped with rare earths into methy silicon oil. It is found that its electrorheological (ER) effect improves strikingly after loading electric field. At a certain concentration, the immediate viscosity increases from 95 to 178 Pa·s compared to the system without doping.展开更多
A valid experimental setup was proposed to study the wave transfer in PDMS fluids. It is found that the degree of attenuation in strain rate is greater with the increasing fluid viscosity, increasing vibration frequen...A valid experimental setup was proposed to study the wave transfer in PDMS fluids. It is found that the degree of attenuation in strain rate is greater with the increasing fluid viscosity, increasing vibration frequency, and increasing wave traveled distance.展开更多
A parallel dynamic passive valveless micropump was designed, which consists of three layers-valve, diaphragm and electromagnetic coil. The valve was wetly etched in a silicon wafer, the diaphragm was a PDMS (polydime...A parallel dynamic passive valveless micropump was designed, which consists of three layers-valve, diaphragm and electromagnetic coil. The valve was wetly etched in a silicon wafer, the diaphragm was a PDMS (polydimethyl siloxane) film spun on a silicon wafer with embedded permanent magnet posts, and the coil was electroplated on a silicon substrate. Under the actuation of the magnetic field generated by coils, the flexible diaphragm could be displaced upwards and downwards. After analyzing magnetic and mechanical characteristic of the flexible membrane and direction-dependence of the nozzle, a micropump was designed. And the relative length (L/d) of the micropump nozzle was taken 4. A 7 × 7 array of permanent magnetic posts was embedded in the PDMS film. Two diaphragms worked in an anti-step mode, which could relieve the liquid shock and increase the discharge of the micropump. The ANSYS and Matlab were adopted to analyze the actuation effect of the coil and the flow characteristic of the micropump. Results show that when actuated under a 0.3 A, 100 Hz current, the displacement of the diaphragm is more than 30 μm, and the discharge of the micropump is about 6 μL/s.展开更多
Poly(lithium propionate methyl siloxane )as a single-ion carrier source was synthesized. The crosslinked film showed lower lithium ionic conductivity at room temperature (about 10^(-10) S/cm). However,the lithium ioni...Poly(lithium propionate methyl siloxane )as a single-ion carrier source was synthesized. The crosslinked film showed lower lithium ionic conductivity at room temperature (about 10^(-10) S/cm). However,the lithium ionic conductivity was obviously increased by blending with high polar polymers such as polyethylene oxide, poly (methylsiloxane - co- ethylene oxide) and poly (methylsiloxane- g- ethylene oxide). In the blend system a high conductivity of 10^(-7)-10^(-5) Scm^(-1) at room temperature was obtained and the single-ion conductivity was deeply influenced by the content of the poly (lithium propionate methyl siioxane). The dc ionic conductivity of the flexible crosslinked films is more stable over time.展开更多
As restorative dentists, we are faced everyday with decisions about which impression materials and techniques should be used when restoring teeth. The challenge becomes bigger when the patients present with open gingi...As restorative dentists, we are faced everyday with decisions about which impression materials and techniques should be used when restoring teeth. The challenge becomes bigger when the patients present with open gingival embrasures, the dreaded “black triangles”, which tops the list of dentist frustration while taking the impression and after preparation of veneers, crowns, bridges, etc. The technique described offers an option to avoid problems related to impressions locking in gingival embrasures and tearing on removal.展开更多
We investigated the aging effect on the chemical structure of silicone rubber composite materials under outdoor environment. The variations of low molecular weight siloxanes in silicone rubber were probed by gas chrom...We investigated the aging effect on the chemical structure of silicone rubber composite materials under outdoor environment. The variations of low molecular weight siloxanes in silicone rubber were probed by gas chromatography-mass spectrometry during the degradation process. The experimental results indicate that a series of cyclic siloxanes exist in both the virgin and aged silicone rubber samples, while the additional low molecular weight siloxanes(hexamethyl cyclotrisiloxane) only appear in the aged samples. Meanwhile, the total amounts of low molecular weight siloxanes in the aged samples are much less than those in the virgin ones. The loss of low molecular weight siloxanes is induced by the chain scission and depolymerization.展开更多
基金financial support from the National Natural Science Foundation of China (21677046)the Natural Science Foundation of Hebei Province (B2017205146)
文摘Biogas can be used as an alternative energy source for producing heat and electricity;however, volatile methylsiloxanes(VOSiC) present in biogas can severely damage heat exchangers, turbines and gas engines. Consequently, e cient removal of VOSiC from biogas that is used as a biofuel is required. In this work, acetylated silica gel(Ac@SG) was synthesized,via treatment of microporous silica gel(SG) with acetic anhydride as an adsorbent, for removal of VOSiC from biogas,and characterized with XRD, SEM–EDS, N2-BET and FT-IR. This Ac@SG adsorbent exhibited a meso-/microporous structure and hydrophobic surface, indicating it was a more e cient adsorbent for removing hexamethyldisiloxane(L2) and octamethylcyclotetrasiloxane(D4) from biogas samples than conventional SG. It was found that the adsorption capacities of Ac@SG reached 304 mg L2/g for hexamethyldisiloxane and 916 mg D4/g for octamethylcyclotetrasiloxane at lower temperatures in the experimental range, and water had no significant e ect on its absorption e ciency. The used Ac@SG could be easily regenerated by heating it at 110 °C, and the adsorption capacity of recycled Ac@SG for hexamethyldisiloxane and octamethylcyclotetrasiloxane was kept constant in four recycle adsorption experiments.
基金Funded by the National Natural Science Foundation of China(No.21865017)。
文摘The reactive diluent prepared by siloxane modified Trimethylene oxide can improve the performance of the UV curing system.Therefore,1,7-bis[(3-ethyl-3-methoxyoxacylobutane)propyl]octadecylosiloxane(BEMOPOMTS)was synthesized from diethyl carbonate,trimethylopropanes,allyl bromide,and 1,1,3,3,5,5,7,7-octadecylosiloxane as the main raw materials.BEMOPOMTS can be used as reactive diluents in the field of cationic UV curing.It has good thermal stability,and the addition of BEMOPOMTS significantly improves the tensile strength and elongation at break of epoxy resin.Compared with the pure epoxy resin,adding 20%BEMOPOMTS increased the elastic modulus by 25%to 677 MPa.
基金supported by the National Natural Science Foundation of China(No.21407097)Supported by Shandong Key Laboratory of Water Pollution Control and Resource Reuse(No.2019KF14)the Opening Project of Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention(LAP^3)(No.FDLAP17001)
文摘Landfill biogas is a potential alternative for fossil fuel,but the containing impurities,volatile methyl siloxanes(simplified as siloxanes),often cause serious problems in gas turbines when applied to generate electricity.In this research,a collecting and analyzing method based on solvent adsorption and purge and trap-gas chromatography-mass spectrometry was established to determine the siloxanes in biogas from a landfill in Jinan,China,and adjacent ambient samples,such as soil,air,and leachate of the landfill.The results showed that,octamethylcyclotetrasiloxane(D4)and decamethylcyclopentasiloxane(D5)accounted for 63%of total siloxanes;and without considering D4 and D5,the order of detected siloxanes in concentration was found relating to Gibbs free energies of molecules,namely that higher abundant siloxane(except for D4 and D5)usually had lower Gibbs free energy.Additionally,the mass ratio between D4 and octamethyltrisiloxane(L3)in the bio gas varied with different garbage age in landfills,possibly revealing the breaking-down of larger siloxane molecules with time.The samples,which were collected from environmental samples adjacent to the landfill,such as soil,water,and air,presented much higher siloxane level than urban or rural area away from landfills.The current H2 S scrubber of the landfill biogas could decrease the total siloxanes from 10.7 to 5.75 mg/m^3 due to Fe2 O3 and a refrigerant drier in a purification system and cyclic siloxanes were more easily removed than linear ones.
基金Financial supports from the National Natural Science Foundation of China(No.50273035)Hangzhou Zhijiang Silicone Chemical Industry Co.,Ltd.are acknowledged.
文摘Siliconated polyurethane (Si-PU) was synthesized using isophorone diisocyanate (IPDI), hydroxybutyl-terminated polydimethylsiloxane (PDMS), polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), 1,6-hexanediol (HDO), dimethylol propionic acid (DMPA) and triethylamine (TEA). Based on butyl acrylate (BA), 2, 2, 2-trifluoroethylmethacrylate (TFEMA) and Si-PU as a seed emulsion, a novel core-shell type acrylic-polyurethane hybrid emulsion, containing siloxane and fluorine (F-Si-PU), was prepared by seeded emulsion polymerization. The contents of siloxane and fluorine were determined according to the feed ratio. Fourier transform infrared spectroscopy (FTIR) was used to identify the chain structures of Si-PU and F-Si-PU. Investigation of transmission electron microscopy (TEM) confirmed the core-shell structure of F-Si-PU emulsion. Measurement results of water contact angle and the swelling ratio in water and n-octane for cured film showed that the water and the oil resistances for F-Si-PU had been significantly improved at a suitable content of fluorine and siloxane.
基金Funded by the National Natural Science Foundation of China(No.51808329)Science and Technology Department of Shanxi Province International Cooperation(No.201603D421027)the Special Project of Commercialization of Shanxi Province Research Foundation(No.201804D131034)
文摘In order to inhibit and remove the thin ice and extend the lifetime of the damaged bridge, the self-healing mechanism and hydrophobic performance of asphalt modified by siloxane and polyurethane (ASP) were studied by dynamic shear rheology (DSR), fluorescence microscope (FM), atomic force microscope (AFM), the fracture-healing-re-fracture test and molecular simulations. The experimental results indicated that the selfhealing capability of ASP increased with increasing heating time and temperature. Furthermore, the addition of siloxane could improve the reaction energy barrier and complex modulus, and it is believed that the self-healing is a viscosity driven process, consisting of two parts namely crack closure and properties recovery. Contact angle of ASP increased with the increasing siloxane content and it deduced that the siloxane could improve the hydrophobic performance of ASP and the ASP molecule model could simulate well the self-healing mechanism and hydrophobic performance of ASP.
基金support of the National High Technology Research and Development Program of China(No.2002305205)the National Basic Research Program of China(No.51320006)
文摘Poly[(methylsilylene ethynylene phenylene ethynylene)-co-(tetramethyldisiloxane ethynylene phenylene ethynylene)]was synthesized by polycondensation reaction of m-diethynylbenzene magnesium reagent with 1,3-dichlorotetramethyldisiloxane and dichloromethylsilane.The copolymer was characterized by FT-IR,~1H NMR,differential scanning calorimetry and thermogravimetric analysis.The results show that the copolymer exhibits good processability and cures at low temperatures.The cured copolymer shows high thermal stability.
文摘Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynamic mechanical property analysis. The results showedthat the introduction of chloromethyl group into polysiloxane increased its polarity and henceimproved the miscibilities with polytetramethylene oxide and polyurethane hard segment.Particularly, in the case of N-methyldiethanolamine extended materials, the surface and tensileproperties of these samples can be adjusted by various ratios of two soft segments.
文摘Porous and bioactive gentamicin sulfate-loaded gelatin-siloxane hybrids were successfidly synthesized by using a combined sol-gel processing, post-gelation soaking, and freeze-drying process. A bone-like apatite layer was able to form in the Ca^2+-containing porous gentamicin-loaded hybrids upon soaking in a simu- lazed body fluid (SBF) up to 1 day. The drug release of gentamicin sulfate was with a burst, followed by an almost constant release up to 7 days. And the rate of release in acidic medium was lower than that in the neutral and basic media.
文摘A hybrimer based on epoxy resin and phenyl-siloxane was prepared by polymerization and a solgel condensation reaction in which Eporite-904 (807 g/eq) bisphenol-A-type epoxy resin, 3-isocyanatopropyltriethoxysilane (IPTES) and phenyltriethoxysilane (PTEOS) acted as precursors. The thermal and optical properties of the epoxy/siloxane hybrimer were studied. The thermogravimetric analysis (TGA) results implied that the hybrimer could increase the crosslink density and enhance the thermal properties. The optical properties were measured after thermal and UV aging. The refractive indexes of the epoxy/siloxane hybrimers were 1.66 - 1.70, and the transmittances of the cured hybrimers were above 90% in the visible wavelength. After a 120°C/24-h thermal aging test, the decreases in the refractive index and transmittance were less than 5% and 20% respectively. The epoxy/siloxane hybrimers also showed low discoloration upon thermal aging at 120°C for 24 h under an air atmosphere.
基金This work was financially supported by the Education Department of Hubei Province (2000Z24002).
文摘A homogeneous longtime stabilized transparent nanometer TiO2 organic solution was obtained by means of the simultaneous hydrolysis and co-polycodensation of tetrabutyltitanate (TBT) and methacryloxypropyltrimethoxysilane (MAPTMS) by the sol-gel process. The particle size of nanometer titanium dioxide was controlled by use of bifunctional silanes, such as diphenyldimethoxysilane (DPDMS), diphenyldiethoxysilane (DPDES) and dimethyldiethoxysilane (DMDES). The effect of TiO2 content in the solution on the refractive index of system was discussed in detail. The result shows that the refractive index of solution increases linearly with TiO2 content. The refractive index of the three hybrid nanometer materials attained 1.6053, 1.5846 and 1.5346, respectively. The size of nanometer particles was characterized by TEM and the particle diameter thus obtained is in the range of 20-90 nm. FT-IR spectra of the materials show that the Ti— O—Si bond is formed.
文摘Poly(methyl methacrylate) (PMMA) was used to wrap alumina siloxane sol through emulsion polymerization. A kind of suspensions with notable ER effect was produced by fully mixing the prepared microcapsule with silicon oil. Meanwhile a series of PMMA wrapped alumina-siloxane gel doped with rare earths was obtained and its ER effect was tested, like viscosity of different rare earth ion doped samples in different powder concentrations and at different temperatures, at the same time, leak current density and dielectric constant were measured. Results show that the ER effect of this suspension is remarkable, and its stability is much better. The condition of emulsion polymerization and the mechanism of effect are discussed.
基金Funded by the National Natural Science Foundation of China(No.21865017)。
文摘A compound,3-ethyl-3-hydroxymethyloxetane(EHO),was synthesized with diethyl carbonate and trihydroxypropane as raw materials,3-ethyl-3-allylmethoxy oxetane(EAMO)was synthesized with EHO and allyl bromide,and 1,1,3,3,5,5-hexamethyl-1,5-bis[(3-ethyl-3-methoxyoxetane)propyl]trisiloxane(HMBEMOPTS)was synthesized with EAMO and 1,1,3,3,5,5-hexamethyltrisiloxane(HMTS).HMBEMOPTS is a novel UV-curable oligomer.The test of photo-DSC shows the photosensitivity of HMBEMOPTS is better than the ordinary oxetane,3-ethyl-3-[(3-ethyloxetan-3-yl)methoxymethyl]oxetane.HMBEMOPTS was mixed with bisphenol A type epoxy resin E-51 to prepare a cationic UV-curable system,and triarylsulfonium hexafluoroantimonate(UV-6976)was used as a cationic photoinitiator.The mechanical tests of coating films prove that when the mass fraction of HMBEMOPTS is 50%,the mechanical properties of the curing system are the best.The impact strength of the UV-curable films is measured to be 40 kg·cm and the flexibility is 2 mm;the tensile strength and flexural strength of the prepared specimens are 20.74 MPa and 13.43 MPa,respectively.The experimental results show that HMBEMOPTS can effectively improve photosensitivity and flexibility of the photosensitive resin.
文摘PMMA wrapped alumina siloxane gel was obtained by using poly (methyl methacrylate) (PMMA) to wrap alumina siloxane sol which was made from water glass, aluminum nitrate and α methacrylic acid. Meanwhile, rare earth ions were used to dope in the course of reaction, and stable suspensions was produced by putting PMMA wrapped microcapsule powder doped with rare earths into methy silicon oil. It is found that its electrorheological (ER) effect improves strikingly after loading electric field. At a certain concentration, the immediate viscosity increases from 95 to 178 Pa·s compared to the system without doping.
文摘A valid experimental setup was proposed to study the wave transfer in PDMS fluids. It is found that the degree of attenuation in strain rate is greater with the increasing fluid viscosity, increasing vibration frequency, and increasing wave traveled distance.
文摘A parallel dynamic passive valveless micropump was designed, which consists of three layers-valve, diaphragm and electromagnetic coil. The valve was wetly etched in a silicon wafer, the diaphragm was a PDMS (polydimethyl siloxane) film spun on a silicon wafer with embedded permanent magnet posts, and the coil was electroplated on a silicon substrate. Under the actuation of the magnetic field generated by coils, the flexible diaphragm could be displaced upwards and downwards. After analyzing magnetic and mechanical characteristic of the flexible membrane and direction-dependence of the nozzle, a micropump was designed. And the relative length (L/d) of the micropump nozzle was taken 4. A 7 × 7 array of permanent magnetic posts was embedded in the PDMS film. Two diaphragms worked in an anti-step mode, which could relieve the liquid shock and increase the discharge of the micropump. The ANSYS and Matlab were adopted to analyze the actuation effect of the coil and the flow characteristic of the micropump. Results show that when actuated under a 0.3 A, 100 Hz current, the displacement of the diaphragm is more than 30 μm, and the discharge of the micropump is about 6 μL/s.
基金This work was supported by the National Natural Science Foundation of China
文摘Poly(lithium propionate methyl siloxane )as a single-ion carrier source was synthesized. The crosslinked film showed lower lithium ionic conductivity at room temperature (about 10^(-10) S/cm). However,the lithium ionic conductivity was obviously increased by blending with high polar polymers such as polyethylene oxide, poly (methylsiloxane - co- ethylene oxide) and poly (methylsiloxane- g- ethylene oxide). In the blend system a high conductivity of 10^(-7)-10^(-5) Scm^(-1) at room temperature was obtained and the single-ion conductivity was deeply influenced by the content of the poly (lithium propionate methyl siioxane). The dc ionic conductivity of the flexible crosslinked films is more stable over time.
文摘As restorative dentists, we are faced everyday with decisions about which impression materials and techniques should be used when restoring teeth. The challenge becomes bigger when the patients present with open gingival embrasures, the dreaded “black triangles”, which tops the list of dentist frustration while taking the impression and after preparation of veneers, crowns, bridges, etc. The technique described offers an option to avoid problems related to impressions locking in gingival embrasures and tearing on removal.
基金Funded by the National Natural Science Foundation of China(21174108)the Science and Technology Project of China Southern Power Grid Co.,Ltd.(K-GD2014-185)
文摘We investigated the aging effect on the chemical structure of silicone rubber composite materials under outdoor environment. The variations of low molecular weight siloxanes in silicone rubber were probed by gas chromatography-mass spectrometry during the degradation process. The experimental results indicate that a series of cyclic siloxanes exist in both the virgin and aged silicone rubber samples, while the additional low molecular weight siloxanes(hexamethyl cyclotrisiloxane) only appear in the aged samples. Meanwhile, the total amounts of low molecular weight siloxanes in the aged samples are much less than those in the virgin ones. The loss of low molecular weight siloxanes is induced by the chain scission and depolymerization.
基金supported by the National Natural Science Foundation of China(52203064,51873110)Sichuan Science and Technology Program(2022YFG0115 and 2021JDJQ0018)+2 种基金Sichuan Science and Technology Program-Natural Science Foundation of Sichuan Province(2022NSFSC1982)the Fundamental Research Funds for the Central Universities(2022SCU12011)the State Key Laboratory of Polymer Materials Engineering。