Silane Functional Groups Research Articles

Effect of Fiber Surface Treatment on Mechanical Properties of Polylactic Acid/Empty Fruit Bunch Fiber Biocomposites

Renewable resourced green biocomposites are currently receiving much attention due to their environmental advantages. Therefore, the aim of this research is study the effect of fiber surface treatment on the mechanical properties of polylactic acid (PLA) biocomposite in order to produce a green biocomposite. Experiments were conducted by surface treatment of empty fruit bunch fiber using two methods, sodium hydroxide and silane. Both treated and untreated fibers were then melt compounded with PLA and mechanical properties of the biocomposite was studied. The results showed that silane treatment improved the reinforced biocomposite mechanical properties such as tensile strength by 33% and flexural modulus by 44% compared with untreated fiber reinforced biocomposites. This is due to the silane functional groups that act as a bridge between the PLA and fiber.

The effects of silane coupling agents on the properties of PHBV/halloysite nanocomposites

The aim of this work was to characterize poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposites with halloysite nanotube (HNT) filler, both natural HNT and HNT modified with different functionalized organosilanes. Nanocomposites with 3wt.% HNT were obtained by melt processing in a twin screw co-rotating extruder. The nanocomposites were characterized in terms of their morphology and thermal and mechanical properties. TEM images provided evidence of the nanocomposite formation. The incorporation of modified HNT altered the mechanical properties of the material depending on the silane functional group responsible for interacting with the polymer. The HNT modified with aminosilanes did not exhibit the expected reinforcing effect. It is possible that the amino group reacted with the carbonyl group of PHBV, changing its chemical structure and thus its final properties. A thermo-mechanical study and TGA results corroborated these findings, indicating a lower viscosity and a decrease in the degradation temperatures of the polymer in the presence of aminosilane-modified HNT.

Effects of Carbon Loading on the Performance of Functionalized Carbon Nanotube Polymer Heat Sink for High Power Light-Emitting Diode in Switching Applications

The functionalized carbon nanotube has been shown to be a viable filler material to increase the thermal conductivity of elastomer heat sinks. However, the effect of the amount of fillers used, that is, the carbon loading in elastomers is still unknown. This study focuses on varying the carbon loading percentage, in 0.2 wt% increment (0.2, 0.4, etc.), to quantify the performance improvements of the elastomer heat sinks. The carbon nanotubes were functionalized with short-chain silane functional groups to allow the blend to be more miscible. This process also allows the formation of a heat spreading network of carbon nanotubes utilizing the phonon transfer mechanism well known for this type of fillers. The performance indicators are the heat spreading signatures evolution in 30 min of infrared thermal imaging and the extent of the cumulative structure function of the heat sinks when high power LEDs are mounted directly on the plastic heat sinks as a heat source. The results show an interesting change in the heat transfer mechanism for heat sink with higher carbon loading as compared to those with lower carbon loading. The boundary for such change in heat transfer occurs at 0.6 wt% of carbon nanotube. Finally, the results are compared to an aluminum heat sink of similar size and we find that the heat dissipation for the heat sink with higher carbon loading performs better than the aluminum heat sink. This indicates that functionalized carbon nanotubes loaded heat sink has the potential of replacing aluminum heat sinks especially in the weight sensitive application with a 25% reduction in weight.

Surface modification of a biodegradable magnesium alloy with phosphorylcholine (PC) and sulfobetaine (SB) functional macromolecules for reduced thrombogenicity and acute corrosion resistance.

Siloxane functionalized phosphorylcholine (PC) or sulfobetaine (SB) macromolecules (PCSSi or SBSSi) were synthesized to act as surface modifying agents for degradable metallic surfaces to improve acute blood compatibility and slow initial corrosion rates. The macromolecules were synthesized using a thiol-ene radical photopolymerization technique and then utilized to modify magnesium (Mg) alloy (AZ31) surfaces via an anhydrous phase deposition of the silane functional groups. X-ray photoelectron spectroscopy surface analysis results indicated successful surface modification based on increased nitrogen and phosphorus or sulfur composition on the modified surfaces relative to unmodified AZ31. In vitro acute thrombogenicity assessment after ovine blood contact with the PCSSi and SBSSi modified surfaces showed a significant decrease in platelet deposition and bulk phase platelet activation compared with the control alloy surfaces. Potentiodynamic polarization and electrochemical impedance spectroscopy data obtained from electrochemical corrosion testing demonstrated increased corrosion resistance for PCSSi- and SBSSi-modified AZ31 versus unmodified surfaces. The developed coating technique using PCSSi or SBSSi showed promise in acutely reducing both the corrosion and thrombotic processes, which would be attractive for application to blood contacting devices, such as vascular stents, made from degradable Mg alloys.

Dispersion of water into oil in a rotor–stator mixer. Part 2: Effect of phase fraction

In Part 1 (Rueger and Calabrese, 2013), we monitored dilute water-in-oil dispersions in a batch Silverson L4R rotor–stator mixer to establish breakage mechanisms and develop a mechanistic basis for correlation of equilibrium mean drop size. In this study (Part 2) we consider the effect of water phase fraction under similar processing conditions, thereby requiring consideration of coalescence. Most of the work on the effect of phase fraction in stirred vessels was done with a low-viscosity continuous phase in turbulent flow with inertial subrange scaling (d>η). For that case drop size increases linearly with phase fraction, ϕ. In this study, viscous oils comprised the continuous phase, with water as the drop phase. The equilibrium DSD was measured in both laminar and turbulent flow conditions. The diameter of the largest drops was always less than the Kolmogorov microscale (d<η). A much greater increase (than the aforementioned linear relationship) in drop size with phase fraction was observed for ϕ≤0.05; including cases where an oil soluble surfactant was present and where metal mixing head surfaces were rendered hydrophobic by treatment with silane functional groups. It is argued that this significantly greater dependence on ϕ is due to the flow field being locally laminar near the drops with coalescence rate being strongly affected by the collision efficiency, which depends on the viscosity of both phases. The presence of surfactant decreased drop size. The silane treatment decreased drop size; possibly by altering water drop interactions with mill head surfaces. Additional experiments were performed at higher phase fraction, where surfactant was required to stabilize the emulsion. The equilibrium drop size was found to plateau for 0.10<ϕ<0.50. The high phase fraction behavior is attributed to the competing rates of coalescence and breakage and their dependence on ϕ and drop size.

희토류 원소의 분리를 위한 표면 개질 된 메조 다공성 실리케이트의 개발에 관한 연구

자기 조립 분자 집합체 물질인 CMPO로 표면개질 된 메조 다공성 실리케이트를 가수분해와 축합반응을 이용하여 합성하였다. 손님 물질인 CMPO는 2-(diphenylphosphoryl) acetic acid와 3-(triethoxysilyl) propan-1-amine의 아마이드 결합반응을 이용하여 합성하였으며, MCM-41, SBA-15 그리고 실리카 나노입자와 같은 다양한 메조 다공성 실리케이트는 주인물질로 채택하였다. 메조 다공성 실리케이트의 비표면적은 680 <TEX>$m^2/g$</TEX>~1310 <TEX>$m^2/g$</TEX>의 넓이로 측정되었으며 BJH 방법을 이용해서 동공의 크기를 확인한 결과 2.3~9.1 nm 범위의 다양한 크기를 가지고 있었다. 메조 다공성 실리카 중에서는 SBA-15(II)가 가장 높은 약 35 wt%의 CMPO 함유량을 나타내었다. 메조 다공성 실리케이트의 표면에 개질된 CMPO 실란 작용기와 란탄족 이온과의 접근성에 관한 연구 결과, CMPO로 개질 된 모든 흡착제의 경우 상대적으로 이온 반경이 큰 La(III)보다는 크기가 작은 Nd(III)와 Eu(III) 이온을 더 선호하였다. Carbamoylphosphate (CMPO) [CMPO analogue; 2-(diphenylphosphoryl)-N-(3-(triethoxysilyl)propyl)acetamide]silane, as a functional self-assembled molecules, grafted mesoporous silicates were prepared by simple hydrolysis and condensation reaction. Pore sized tailored mesoporous silicates such as MCM-41, SBA-15, or amorphous silica nanoparticles were adopted as host materials. The surface area of ordered mesoporous silicates was ranged from 680 <TEX>$m^2/g$</TEX> to 1310 <TEX>$m^2/g$</TEX> with different pore diameters that estimated to be ca. 2.3~9.1 nm by BJH method. Among the OMMs host materials, SBA-15(II) has higher loading ratio (~35 wt%) of CMPO derivative than other OMMs. Accessibility to CMPO silane functional groups in the surface of mesoporous silicas was studied by lanthanide ions sorption experiments. All of the CMPO modified OMMs favors the smaller Eu(III) and Nd(III) cations than La(III) for relative larger ionic radius.

Synthesis of mesoporous silica grafted with 3-glycidoxypropyltrimethoxy–silane

Hexagonal mesoporous silicas chemically modified with 3-glycidoxypropyltrimethoxy–silane functional groups were synthesized through the post-synthesis of surfactant free mesoporous silica (OSU-6-W). The solid state 29Si NMR, titration method and elemental analysis of the modified samples showed that the average number of pendant groups in these hybrids were around 2.17 and 3.49 group/nm 2, respectively. The surface area analysis showed that these materials have pore diameters of 40.7 and 33.2 Å and surface areas of 966 and 720 m 2/g, respectively. Infrared spectroscopy, solid state NMR for 13C and 29Si nuclei and X-ray diffraction patterns are in agreement with the success of the proposed synthetic procedures, as confirmed for the formation of the mesoporous hybrids. They have shown good performance towards metal-ion adsorption.

Tris(dimethylsilyl)methyllithium: A Reagent for the Synthesis of Vinylbis(silanes) Containing Si–H Functional Groups

Reactions between a series of nonenolisable aldehydes and tris(dimethylsilyl)methyllithium, (HMe2Si)3CLi, are described. The Peterson reaction takes place readily to give vinylbis(silanes). Moreover, styrene and butyl acrylate 1:1 copolymer (P), prepared by use of α,α′-azobis(isobutyronitrile) (AIBN) as an initiator in toluene at 70 ± 1°C, was formylated via direct electophilic substitution by methyl dichloromethyl ether (Cl2CHOMe) in the presence of tin(IV) chloride (SnCl4) in nitrobenzene (PhNO2) as solvent. The reaction of (HMe2Si)3CLi with formyl groups on the side chains of the copolymer led to new macromolecules bearing vinylbis(silane) functional groups.

Electrochemical Behaviors of Silicon Electrode in Lithium Salt Solution Containing Alkoxy Silane Additives

The electrochemical behaviors of a silicon thin-film electrode in organic lithium salt solution were explored with focus on irreversible reactions of the first lithium charge and discharge cycling by using electrochemical quartz crystal microbalance (EQCM) combined with various electrochemical techniques. A considerable increase in mass of the silicon electrode was observed during lithium charging even before lithium absorption into the electrode, which is ascribed to the buildup of electrolyte reduction products on the silicon surface. Galvanostatic charge–discharge experiments combined with ac impedance spectroscopy demonstrate a significant overpotential growth and an aggravating capacity for the lithium charge and discharge cycling, and suggest they are due to the sedimentation of electrolyte reduction product. Additives containing alkoxy silane functional groups were evaluated as a passivation agent for lithium rechargeable batteries utilizing a silicon anode. The presence of additives in electrolyte suppressed the mass accumulation to the silicon electrode caused by irreversible electrolyte reductions and improved the electrode for cycle life. Electrochemical analyses associated with EQCM as a function of the number of alkoxy functional groups of the additives illustrate that the silicon electrode is passivated by chemical reaction of the alkoxy silane functional group of the additives with hydroxyl groups at the electrode/electrolyte interface, and this passivation improves the cycle life.

Structural comparison of products from peroxide‐initiated grafting of vinylsilane and silane‐functionalized nitroxyl to hydrocarbon and polyolefin substrates

AbstractIt has been demonstrated that peroxide‐initiated grafting of vinylsilanes to polyethylene results in a nonuniform distribution of silane groups on the polymer chain due to a chain‐transfer mechanism, leading to inefficient utilization of silane with respect to gel fraction in a crosslinked material. In this article, we demonstrate that grafting a nitroxyl free radical that contains a silane functional group gives a more uniform distribution of silane functionality. Model compounds were synthesized by grafting a silane‐functionalized TEMPO derivative and a vinylsilane to cyclooctane, and their structures were compared. The product grafted with vinyltriethoxysilane consisted of essentially all multigrafted product with an average of 2.26 silane grafts per cyclooctane molecule, which is in close agreement with published data, while the product of grafting the silane‐functional nitroxyl consisted of only the monografted species; no multigrafted product was detected. This confirms that grafting a silane‐functionalized nitroxyl occurs via bimolecular combination of free radicals that is not affected by chain‐transfer and suggests that the process may lead to more efficient utilization of silane as indicated by higher gel fraction for a given level of grafted silane. Synthetic work to prepare silane‐functionalized TEMPO derivatives and preliminary studies to graft them to polyolefins are discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4542–4555, 2008

Structure and properties of GPTMS/DETA and GPTMS/EDA hybrid polymers

Silica/epoxy hybrid polymers were synthesised from 3-glycidoxypropyltrimethoxysilane (GPTMS) by hydrolysis of the silane functional groups in strongly acidic (pH 2) or basic (pH 10) conditions, followed by epoxy ring opening and crosslinking using diethylamine triamine (DETA) and ethylene diamine (EDA). Structural characterization of the hybrid polymers was performed using FTIR spectroscopy. The thermal properties of GPTMS/DETA and GPTMS/EDA hybrid polymers were investigated by differential scanning calorimetry and thermogravimetric analysis, while thermomechanical properties were measured using dynamic mechanical thermal analysis. The influence of pH on the structure and properties of the synthesised GPTMS/DETA and GPTMS/EDA hybrids is discussed.

Spectroscopic characterization of GPTMS/DETA and GPTMS/EDA hybrid polymers

Silica/epoxy hybrid polymers were synthesized from 3-glycidoxypropyltrimethoxysilane (GPTMS) by hydrolysis of the silane functional groups at a range of pHs and water contents of the reaction mixtures, followed by crosslinking by ring opening of the epoxy groups using diethylenetriamine (DETA) or ethylenediamine (EDA). The GPTMS/DETA and GPTMS/EDA hybrid polymers were formed to an extent determined by the mole ratio of active hydrogens from the diamine to epoxy rings ( R H). Structural characterization of the hybrid polymers was performed using Scanning Electron Microscopy (SEM), and Raman, and 13C and 29Si Solid-State Nuclear Magnetic Resonance (NMR) spectroscopies. The results showed that extensive crosslinking occurred for GPTMS/DETA and GPTMS/EDA rigid, homogeneous hybrids with R H = 1, particularly at pH 10.

Effect of Silane Functional Group on Adhesion of Selected Epoxies for Microelectronic Packaging

This paper describes experiments designed to evaluate the effect of various silane surface treatments on the thin-film adhesion of epoxies filled with spherical silicon oxide. Fracture mechanics-based methods evaluated adhesion of both filled and unfilled epoxies to silicon oxide. SEM was used to examine fracture surfaces and evaluate fracture mechanisms. Two different epoxies were tested, including one with four components and multiple intermediate cure reactions. It was found that the only silanes that augmented adhesion of the epoxies to silicon oxide were those with functional groups identical to those of the epoxies which take part in the final curing reaction. However, when these silanes were used to coat filler, adhesion of filled epoxies to silicon oxide wafers remained the same or was slightly reduced. In all cases, fracture occurred at or near the epoxy-wafer interface, suggesting that deformation within the epoxy layer was limited. Only one set of specimens, in which the silane was improperly prepared, resulted in augmented epoxy-wafer adhesion facilitated by filler-matrix delamination. In other words, filled epoxy-wafer adhesion increases with decreasing efficacy of silane adhesion promoter treatment.

Chemical Substituent Effects on Morphological Transitions in Styrene−Butadiene−Styrene Triblock Copolymer Grafted with Polyhedral Oligomeric Silsesquioxanes

A series of hybrid organic/inorganic triblock copolymers of polystyrene−butadiene−polystyrene (SBS) grafted with polyhedral oligomeric silsesquioxane (POSS) molecules with different chemical constituents were synthesized by a hydrosilation method. Four POSS macromers, R‘R7Si8O12, were designed to contain a single silane functional group, R‘, which was used to graft onto the dangling 1,2-butadienes in the polybutadiene soft block and seven identical organic groups, R. Small-angle X-ray scattering and rheological techniques were used to study the effect of sterically similar, yet electronically different, organic R groups, cyclopentyl (Cp), cyclohexyl (Cy), cyclohexenyl (Cye), and phenyl (Ph), on the morphology of SBS triblock copolymer and the order−disorder transition behavior. It was observed that POSS with phenyl moiety, when grafted to the polybutadiene (PB) phase, appears to show favorable interaction with the polystyrene (PS) phase; effectively, the Ph-POSS is plasticizing the SBS due to an effect wh...

Chemistry of Silanes: Interfaces in Dental Polymers and Composites.

The performance and service life of glass-or ceramic-filled polymeric composites depend on the nature of their resin, filler and interfacial phases as well as the efficacy of the polymerization process. The synergy that exists between the organic polymer matrix and the usually inorganic reinforcing filler phase is principally mediated by the interfacial/interphasial phase. This latter phase develops as a result of the dual reactivity of a silane coupling agent, (YRSiX3), a bifunctional molecule capable of reacting with the silanol groups of glass or ceramic fillers via its silane functional group (–SiX3) to form Si-O-Si- bonds to filler surfaces, and also with the resin phase by graft copolymerization via its Y functional group, usually a methacrylic vinyl group. In this paper, we explore some of the chemistry of organosilanes, especially that of functional organosilanes (or silane coupling agents as they are commonly known) that are used to mediate interfacial bonding in mineral reinforced polymeric composites. The chemistry of organosilanes can be quite complex involving hydrolytically initiated self-condensation reactions in solvents (including monomers) that can culminate in polymeric silsesquioxane structures, exchange reactions with hydroxylated or carboxylated monomers to form silyl ethers and esters, as well as the formation of silane derived interfaces by adhesive coupling with siliceous mineral surfaces.

Stable Microstructured Network for Protein Patterning on a Plastic Microfluidic Channel: Strategy and Characterization of On-Chip Enzyme Microreactors

Chemical modification of a poly(methyl methacrylate) (PMMA) microchannel surface has been explored to functionalize microfluidic chip systems. A craft copolymer was designed and synthesized to introduce the silane functional groups onto the plastic surface first. Furthermore, it has been found that, through a silicon-oxygen-silicon bridge that formed by tethering to these functional groups, a stable patterning network of gel matrix could be achieved. Thus, anchorage of proteins could be realized onto the hydrophobic PMMA microchannels with bioactivity preserved as far as possible. The protein homogeneous patterning in a microfluidic channel has been demonstrated by performing microchip capillary electrophoresis with laser-induced fluorescence detection and confocal fluorescence microscopy. To investigate the bioactivity of enzymes entrapped within stable silica gel-derived microchannels, the suggested scheme was employed to the construction of immobilized enzyme microreactor-on-a-chip. The proteolytic activity of immobilized trypsin has been demonstrated with the digestion of cytochrome c and bovine serum albumin at a fast flow rate of 4.0 microL/min, which affords the short residence time less than 5 s. The digestion products were characterized using MALDI-TOF MS with sequence coverage of 75 and 31% observed, respectively. This research exhibited a simple but effective strategy of plastic microchip surface modification for protein immobilization in biological and proteomic research.

Organoclay–natural rubber nanocomposites synthesized by mechanical and solution mixing methods

AbstractThis investigation describes two methods to obtain rubber composites based on natural rubber (NR) and organophilic layered silicates. In order to improve the exfoliation and compatibilization of the organoclays with the rubber matrix, a new approach which involves swelling of the organoclays with an elastomer solution prior to compounding has been used. The effect of the addition during swelling of a coupling agent, namely bis(trietoxysilylpropyl)tetrasulfan (TESPT), on the behaviour of the composites was also investigated. The results show that a low amount of organoclay (10 phr) significantly improves the properties of natural rubber. This suggests a strong rubber–organoclay interaction which is attributed to a high degree of rubber intercalation into the nanosilicate galleries, as was confirmed from X‐ray diffraction. In addition, an ulterior improvement in the properties of the nanocomposites prepared by solution mixing is clearly observed, due to the better filler–rubber compatibility. An even further increase in the properties is observed by treating the silicate with a silane coupling agent. The silane functional groups modify the clay surface, thus reducing the surface energy, and consequently improving the compatibility with the rubber matrix. Copyright © 2004 Society of Chemical Industry

Styrene−Butadiene−Styrene Triblock Copolymers Modified with Polyhedral Oligomeric Silsesquioxanes

A novel hybrid organic/inorganic triblock copolymer of polystyrene−butadiene−polystyrene (SBS) containing grafted polyhedral oligomeric silsesquioxane (POSS) molecules was synthesized by a hydrosilation method. The POSS molecules were designed to contain a single silane functional group, which was used to graft onto the dangling 1,2-butadienes in the polybutadiene soft block. Unlike typical free radical copolymerizations commonly used for many other POSS incorporations investigated, this synthesis method allows us to make a series of polymers with varying amounts of POSS without any change to the overall degree of polymerization or structure of the main SBS backbone. This gives us a unique opportunity to study the POSS behavior in the matrix and know that all differences are solely due to the POSS grafted to the soft continuous butadiene phase. X-ray diffraction revealed that the grafted POSS are very well dispersed in the matrix of the hybrid polymer, which is compared to the strong phase segregation obs...

Modification of cellulosic fibres with functionalised silanes: development of surface properties

The surface modification of cellulosic fibres was carried out using organofunctional silane coupling agents in an ethanol/water medium. A heat treatment (curing) was applied after reaching the equilibrium adsorption of the prehydrolysed silanes onto the cellulosic substrate. The modified fibres were then characterised by diffuse reflectance infrared spectroscopy and contact angle measurements. The presence of Si–O–Cellulose and Si–O–Si bonds on the cellulose surface confirmed that the silane coupling agent was efficiently held on the fibres surface through both condensation with cellulose hydroxyl groups and self-condensation between silanol groups. The change of the surface properties after the modification was ascertained by contact angle measurements and inverse gas chromatographic analysis. It was shown that the silane functional groups appended to the fibre surface could participate in the chain growth of appropriate monomers to give a covalent continuity between the fibres and the ensuing polymer matrix.

Large‐Area Electrochromic Coatings: Composites of Polyaniline and Polyacrylate‐Silica Hybrid Sol‐Gel Materials

A low‐cost technique for fabricating large‐area electrochromic coatings is described. Polyaniline was incorporated into polyacrylate‐silica hybrid sol‐gel networks using suspended particles or solutions. A solution of polyaniline and poly[methyl methacrylate‐co‐3‐(trimethoxysilyl)propyl methacrylate] can be spray‐ or brush‐coated on transparent indium‐tin oxide substrates to form robust electrochromic coatings. Silane functional groups on the polyacrylate chain act as coupling and cross‐linking agents to improve surface adhesion and mechanical properties of the resulting composite coatings. These coatings showed reversible transparent to green color change when polarized at potentials between ‐0.4 and + 0.4 V vs. Ag/AgCl in a 0.2 M /acetonitrile electrolyte solution. The cycle lifetimes of polyaniline films were improved by incorporating the polymer in the polyacrylate‐Silica matrix. Electrochromic switching was demonstrated for the composite coatings in large‐area all‐solid‐state devices.