Silane Crosslinking Research Articles

M2Y8(SiO4)6O2: Tb3+ (M=Ca, Sr) phosphors: Sol–gel synthesis from N-2-aminoethylic-3-aminopropyldiethoxysilane and different photoluminescence behavior

Abstract M 2 Y 8 (SiO 4 ) 6 O 2 : Tb 3+ (M = Ca, Sr) phosphors have been synthesized with a new silicon source silane crosslinking reagent (N-2-aminoethylic-3-aminopropyldiethoxysilane [NH 2 (CH 2 ) 2 NH(CH 2 ) 3 SiCH 3 (OCH 3 ) 2 ], abbreviated as AEAPMMS) through the sol–gel process, both of which present the characteristic emission 5 D 4 → 7 F J ( J = 6, 5, 4, 3) of Tb 3+ ions. It is interesting to be found that the high energy level blue emission ( 5 D 3 → 7 F J ( J = 6, 5, 4, 3) transition) still can be found in the emission spectrum of Ca 2 Y 8 (SiO 4 ) 6 O 2 : Tb 3+ while it disappears in the emission spectrum of Sr 2 Y 8 (SiO 4 ) 6 O 2 : Tb 3+ for the cross-relaxation-induced quenching.

Molecular structure and fracture properties of ZrOX/Epoxysilane hybrid films

The mechanical reliability of hybrid films depends critically on their fracture properties which are controlled largely by the film composition and molecular structure. We have investigated the adhesive and cohesive fracture properties of hybrid films processed from 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetra n-propoxyzirconium (TPOZ), for which the roles of molecular structure and composition have not been well established. The influences of film Zr/GPTMS ratio, silane crosslinking, and substrate composition on fracture resistance were quantified in terms of the critical strain energy release rate, GC Film fracture energy was found to increase, then decrease with increasing Zr/GPTMS ratio. Removal of the epoxy rings of GPTMS from the film was found to drastically decrease the cohesive fracture energy of the film as well as the adhesive fracture energy of the film/epoxy interface. Finally, films deposited on silicon had much higher fracture energies compared to those deposited onto aluminum and titanium from identical sols. FTIR, XPS, and AFM were used to characterize the film structure and fracture surfaces. The molecular-scale mechanisms responsible for the observed trends are discussed. These results provide new insights into the interaction between the substrate chemistry, molecular structure, and mechanical reliability of hybrid sol-gel films.

Resin Bonding to Silicatized Zirconia with Two Isocyanatosilanes and a Cross-linking Silane. Part I: Experimental

In this study we have investigated the effects of the chain length of hydrolyzable groups in two isocyanato silane coupling agents, 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane, on the shear bond strength of resin attached to silicatized zirconia. In addition, the effects of varying the silane concentration (at 0.1 vol% and 1.0 vol%) with or without the addition of a cross-linking silane (0.05 vol% or 0.5 vol% bis-1,2-(triethoxysilyl)ethane) were assessed. It was concluded that the use of the experimental primer of 3-isocyanatopropyltrimethoxysilane at either 0.1 vol% or 1 vol% with cross-linking silane resulted in significantly higher shear bond strengths than the use of primer without the cross-linking silane.

Resin Bonding to Silicatized Zirconia with Two Isocyanatosilanes and a Cross-linking Silane. Part II: Mechanistic Approach

In this paper we discuss and interpret the results of shear bond strengths achieved after the use of two silane coupling agents with isocyanato functionality, viz. 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane. The silanes were used alone and also blended with a non-functional cross-linking silane on silicatized zirconia before light-curing of resin stubs on the surface, as described elsewhere in the first part of our study (see “Part I: Experimental”). A series of reaction mechanisms and conceptual diagrams are also presented. The reaction mechanisms illustrating the effect of adding a cross-linking silane into a silane blend, the silane hydrolysis and the behavior of two organofunctional groups (isocyanate and alkene) of silanes upon reaction with Rely X Unicem Aplicap resin-composite cement are discussed in detail.

Promotion of Adhesion Between Resin and Silica-coated Titanium by Silane Monomers and Formic Acid Catalyst

Three bifunctional silane coupling agent monomers and their blends with a cross-linking silane were investigated as six experimental adhesion-promoters in vitro. Three organosilane monomers, 3-methacryloxypropyltrimethoxysilane, styrylethyltrimethoxysilane, and 3-(N-allylamino)propyltrimethoxysilane, were prepared as 1% (v/v) primers and also blended with a cross-linking silane, 1,2-bis-(triethoxysilyl)ethane at 0.5% (v/v), in a 95:5 solution of ethanol in deionized water. The silanes were allowed to hydrolyze using formic acid as catalyst and were applied to a substrate of silica-coated Ti. The control was a pre-hydrolyzed silane coupling agent that is commonly used in dentistry. An experimental unfilled bis-phenol-A-diglycidyldimethacrylate/methylmethacrylate resin was bonded by photo-polymerization as stubs to the prepared Ti. Half of the specimens were artificially aged by wet thermo-cycling and half were stored in dry conditions in a desiccator. Storage conditions and the type of primer silane or blend significantly affected shear bond strength values. 3-Methacryloxypropyltrimethoxysilane, alone or blended, produced significantly higher shear bond strength values than the control, both after dry storage and after thermo-cycling.

Experimental Novel Silane System in Adhesion Promotion between Dental Resin and Pretreated Titanium. Part II: Effect of Long-Term Water Storage

In this study we have assessed the effect of long-term water storage at 37oC on silane-aided adhesion promotion. Five experimental silane blends were evaluated as adhesion-promoters. First, five functional organosilane monomers (silicon esters), 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, tetrakis-(2-methacryloxyethoxy)silane and bis-[3-(triethoxysilyl)propyl]tetrasulfide, were diluted to 1% (v/v) in 95% ethanol and blended with a non-functional cross-linking silane, bis-1,2-(triethoxysilyl)ethane (1%). A commercially available pre-activated silane product was used as the control. After activation by hydrolysis, each primer blend was applied to silica-coated Ti coupons. Stubs of experimental bis-phenol-A-diglycidyldimethacrylate (bis-GMA)-based resin were bonded by photo-polymerization onto the pretreated Ti coupons. Half of the specimens were stored in deionized water for 6 months and half for 12 months. The primer containing 3-acryloxypropyltrimethoxysilane and bis-1,2-(triethoxysilyl)ethane produced significantly higher shear bond strengths than the control silane and other experimental silane primers after both periods of storage.

Garnet particles effect on the cross-linking of PDMS and the network structures formed

Poly(dimethylsiloxane) (PDMS) cross-linked films with different concentrations of micrometer-sized garnet particles were prepared through hydrosilylation reaction between a di-vinyl-terminated PDMS and a four-functional silane cross-linker in the presence of a Platinum catalyst. The garnet particles, consisting of micrometer-sized Ce doped Y3Al5O12 particles commonly used on light converters (for solid state light devices, e.g. Light emitting diodes LEDs), were homogeneously and individually dispersed through the bulk of the cross-linked films for a concentration up to 20% in volume.The effect of the garnet on the cross-linking of the composite films was investigated by in-situ ATR-FTIR Spectroscopy. When formulations with an excess of cross-linker were used the overall consumption of Si–H groups of the cross-linker is slowdown in the presence of the garnet. The same effect was observed for an increasing concentration of the garnet. This effect is attributed to a strong interaction of the catalyst with the garnet during the cross-linking process. The possible origins of this interaction are discussed.NMR Imaging was used to investigate the cross-linked networks formed in the composite films. All the networks are homogeneous through the depth of the cross-linked composite films (approx. 5μm resolution). The films prepared in the presence of the garnet particles showed similar relaxation behavior, regardless of the cross-linker concentration used in the initial formulation, contrary to previous results with PDMS cross-linked films. This behaviour is explained based on the presence of different type of chemical cross-links, resulting from the occurrence of hydrosilylation and secondary reactions, which are influenced by the interaction between the garnet particles and the catalyst.

Effect of silane-grafting on water tree resistance of XLPE cable insulation

Water treeing is one of the main deterioration phenomena observed in the polymeric insulation of extruded crosslinked polyethylene (XLPE) cables, which can affect the service life of power cables. In this work, we investigated the effect of grafting of a silane (vinyl trimethoxysilane, VTMS) on the resistance of XLPE to water treeing. A series of water-treeing tests, the mechanical and dielectric measurements indicated that the silane-grafting could significantly improve the water tree resistance of the conventional XLPE cable insulation with little influences on its dielectric properties, e.g., the dielectric breakdown strength, dielectric constant and loss tangent, and its mechanical performance. It was found that there exists an optimum value of VTMS concentration (about 0.6 phr) corresponding to the minimum water tree length. The water tree resistance mechanism of silane-grafted XLPE was proposed on the basis of the process of silane hydrolysis and crosslinking. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Experimental Novel Silane System in Adhesion Promotion Between Dental Resin and Pretreated Titanium

Five silane blends were evaluated as experimental adhesion-promoter primers. First, five organosilane monomers (silicon esters), 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, tetrakis-(2-ethyloxyethoxy)silane and bis-[3-(triethoxysilyl)propyl]tetrasulfide, were diluted to 1% (v/v) and blended with a non-functional cross-linking silane, 1,2-bis-(triethoxysilyl)ethane (1%), in 95% ethanol. After activation, each blend was applied to silica-coated Ti coupons. A resin based on bis-phenol-A-diglycidyldimethacrylate was then bonded and photo-polymerized as stubs to the pretreated Ti coupons. Half of the specimens were stored in dry conditions and half were artificially aged by thermo-cycling. The primers containing 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane produced significantly higher shear bond strength values than the control silane, a standard pre-activated product used in clinical dentistry.

Hydrothermal synthesis, physical characterization and photoluminescence of homologous-SBA-15 fabricated with Eu 3+

Two series of Eu 3+-doped homologous-SBA-15 materials (abbreviated as MPTMS-SBA-15: Eu 3+ and CTMS-SBA-15: Eu 3+) have been synthesized by a hydrolysis-controlled technology, in which two novel silane crosslinking reagents (3-(methacryloyloxy) propyltrimethoxysilane (MPTMS) and 3-(chloropropyl) trimethoxysilane (CTMS)) are used as silicate precursor instead of traditional tetraethoxysilane (TEOS). It can be found that the different silicate precursors with different functional groups have influence on the physical properties of the corresponding homologous materials. In comparison to the pure SBA-15, the BET surface area and pore size of the modified mesoporous materials have been changed. Finally, the characteristic luminescence is observed for the 5D 0 → 7F J ( J = 0, 1, 2) transition of Eu 3+ ion, suggesting that these kind of homologous-SBA-15 materials are potential host for the luminescence of Eu 3+, whose excitation energy can be quenched by Eu 3+ to some extent.

Thermal property improvement of ethylene‐octene copolymer through the combined introduction of filler and silane crosslink

AbstractIn many applications, e.g., wire and cable insulation, hot water pipe, high‐temperature properties of polymer are essential. This article presents the use of silane crosslinking together with the addition of particular filler in improving the thermal and mechanical properties of ethylene‐octene copolymer (EOC). The effects of filler surface characteristics on siloxane network structure developed and final properties of the crosslinked products are discussed. The results show an increase in the decomposition temperature of EOC more than 50°C after modification. Only crosslinked composites are able to withstand the high‐temperature environment of aging test which is beyond the melting temperature of the matrix polymer. The crosslinked composites filled with calcium carbonate show superior properties to those with silica, due to a higher crosslink density and tighter network structure formed. The silane coupling mechanism and the presence of bound polymer on silica surfaces cause difficulties for the crosslink formation in the silica filled systems. However, an advantageous influence of both silane coupling and crosslink reaction in the silica filled composites is seen on the enhanced tensile strength and modulus of the materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Photopatternable ultrathin gate dielectrics for low-voltage-operating organic circuits

We report here a photopatternable ultrathin gate dielectric for the fabrication of low-voltage-operating organic field-effect transistors (OFETs) and inverters. The gate dielectric material is composed of a photocrosslinkable polymer, poly(vinyl cinnamate), and a thermally crosslinkable silane crosslinking reagent, 1,6-bis(trichlorosilyl)hexane. The spin-coated dielectric is photocured with ultraviolet light, which enables fine film patterning via regular photolithography. After thermal curing (at 110 °C), the dielectric showed excellent insulating properties (a leakage current density of ≈10−7 A/cm2 at 2.0 MV/cm) for an ultrathin film thickness of 70 nm, thus reducing the operating voltage of the OFETs and inverters to −5 V.

Effect of Silane Crosslinker on the Thermal Properties of Rice Straw/HDPE Biocomposite

A formulation was designed to produce silane crosslinkable rice straw/high density polyethylene (RSPE) compound suitable for injection molding process. The formulations consist of high density polyethylene (HDPE) as the base polymer, rice straw as the filler, processing aids and a mixture of crosslink chemicals. Crosslink chemicals consist of vinyltrimethoxysilane (VTMO) as crosslinking agent, dicumyl peroxide (DCP) as the initiator, dibutyltin dilaurate (DBTL) as the condensation catalyst. Lignocellulosic material, rice straw was oven dried at 70°C for 24 h, grinded and sieved. A counter rotating twin shaft high speed mixer was utilized to mix the rice straw, HDPE and the processing aids. Blends were then compounded on co-rotating and intermeshing twin screw extruder. Test specimens were prepared via injection molding process followed by oven curing at 90°C. Fourier Transform Infra Red (FTIR) was used to determine the chemical group involved in the crosslinking reaction. Degree of crosslinking in the silane crosslinked compound was measured by determining their gel content. Thermal properties were analyzed on the Differential Scanning Calorimetry (DSC) for the melt temperature, Tm, whereas Thermogravimetric (TGA) analysis for its thermal stability behavior. The degree of crosslinking in RSPE increases with an increased in VTMO and DCP concentration. The results from FTIR showed the presence of Si-O-Si bond and Si-O-C indicative of crosslinks formation. Thermal behavior of the compound illustrated that the crosslinked RSPE was more stable than the uncrosslinked RSPE and pure HDPE, while the Tm was unchanged.

Durable Hydrophobic Textile Fabric Finishing Using Silica Nanoparticles and Mixed Silanes

Cotton fabric surface was treated with combinations of silica nanoparticles, silane hydrophobes, and silane crosslinkers to obtain durable hydrophobicity. Performance analysis was done by measuring the contact angle of water on the treated fabric surface. To evaluate the durability of the surface hydrophobicity, AATCC crocking and laundering tests were performed. Cotton fabrics with good hydrophobicity (contact angle = 139.1°) and excellent durability (e.g. 95% recovery of contact angle after laundering) were obtained when treated with Aerosil® 90 nanoparticles, n-octyltrimethoxysilane, and bis(triethoxysilyl)ethane. This study demonstrated that the surface treatment using silica nanoparticles and mixed silanes is a promising alternative to fluoropolymer chemistry for achieving durable hydrophobic fabrics.

Chemically bonded metallic (Eu, Tb, Zn) hybrid materials through sulfide linkage: Molecular construction, physical characterization and photophysical properties

In this paper, a kind of aromatic carboxylic acid of sulfhydryl group (2-mercaptonicotinic acid) is modified with four silane crosslinking reagents (3-methacryloyloxypropyltrimethoxysilane (S 1), 3-glycidoxypropyltrimethoxysilane (S 2), 3-aminopropyltrimethoxysilane (S 3), and 3-(triethoxysilyl)propylisocyanate (S 4)) to achieve four new kinds of functionalized molecular bridge (P i ( i = 1–4)). Subsequently, four molecular bridges and lanthanides (europium and terbium) or zinc ions have been assembled via chemical bonds through a sol–gel (cohydrolysis and copolycondensation) process with inorganic precursor (tetraethoxysilane, TEOS), resulting in four novel series of chemically bonded hybrid materials which named as Ln (Zn)–M i ( i = 1–4). The coordinated bonding makes metal ions evenly dispersed in a stable hybrid system. The intramolecular energy transfer process between lanthanide ions and the molecular bridges take place within these molecular-based hybrids and especially the luminescent quantum efficiency of them are determined, suggesting that the hybrid material systems derived from different molecular bridges present different luminescence efficiencies.

The impact of silane chemistry conditions on the properties of wood plastic composites with low density polyethylene and high wood content

AbstractSilane chemistry was implemented on various formulations of wood/thermoplastic polymer composites (WPCs) with low density polyethylene (LDPE) and high wood content (60 wt%). Taguchi analysis was used to evaluate the impact of vinyltrimethoxysilane content (VTMS), dicumyl peroxide content (DCP), and processing temperature on the rheological, morphological, and dynamic mechanic properties of WPCs. The torque power was measured by a Haake torque rheometer and indicated that the VTMS content and temperature most significantly impacted the rheological properties related to silane reactions. Differential scanning calorimetry also showed a larger depression in LDPE melting point and crystallinity index when a high VTMS content (35 phr), high DCP content (0.5 phr), and a high compounding temperature (200°C) were used. With dynamic mechanical analysis (DMA), it was shown that the compounded formulations had a higher storage modulus over a wide range of temperature whereas the β transition temperature increased with higher content in silane reactants. Interestingly, the high humidity/temperature conditioning step aimed at crosslinking resulted in a drop of dynamic moduli compared to the freshly compounded formulations. This was explained by the fact that during compounding of LDPE with high wood content and silane reactants, significant amounts of matrix and interfacial silane crosslinking already occurred. Subsequent conditioning in a high humidity and temperature environment was proposed to hydrolyze the interfacial siloxane bonds resulting in a degradation of mechanical properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Influence of Coagents on the Silane Grafting and Cross-linking of Polypropylene

The grafting of vinyltrimethoxysilane (VTMS) onto polypropylene (PP) was carried out in a melt process, and the cross-linking in the hot water. The influence of coagents, i.e., styrene (St), divinylbenzene (DVB), triallyl isocyanurate (TAIC) and trimethylolpropane triacrylate (TMPTA) on the grafting degree, gel percentage, melt flow index (MFI) of the VTMS modified PP were investigated. It was found that the incorporation of the coagents influenced the grafting and cross-linking of VTMS. The crystallization behavior and crystal structure of the coagent assisted VTMS-cross-linked PP were studied by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WXAD), respectively. The thermogravimetric analysis (TG) studies indicate that the thermal stability of VTMS-cross-linked PP was improved by the incorporation of coagents.

Intumescent flame retardation and silane crosslinking of PP/EPDM elastomer

AbstractThis study deals with the silane crosslinking and intumescent flame retardation of polypropylene/ethylene‐propylene‐diene copolymer (PP/EPDM) elastomers. The effect of silane crosslinking on the flame retardancy of the PP/EPDM composites containing melamine phosphate (MP) and dipentaerythritol (DPER) was studied by limiting oxygen index, UL 94 and cone calorimetry tests. The chemical composition of the silane crosslinked and flame retarded PP/EPDM composites treated at different temperatures was studied by X‐ray photoelectron spectroscopy and real time Fourier transform infrared (FTIR) spectrometry. Thermal decomposition and crystallization behavior of the PP/EPDM composites were investigated using thermogravimetric analysis and differential scanning calorimetry, respectively. Moreover, the mechanical properties of the composites were also studied. It is found that the flame retardancy, mechanical properties, and thermal decomposition behavior of the composites are influenced by silane grafting and crosslinking. Copyright © 2008 John Wiley & Sons, Ltd.

Synthesis of carboxymethyl-chitosan/acrylic acid hydrogel using silane crosslinker

AbstractNovel pH sensitive carboxymethyl (CM) chitosan/acrylic acid hydrogels were prepared. CM-chitosan and acrylic acid (AA) in aqueous solution were copolymerized and crosslinked by using vinyltriethoxysilane (VTESi). Different amounts of AA and crosslinker were incorporated in CM-chitosan/AA hydrogel. IR analysis confirmed the presence of pyranose ring as well as Si-O-Si linkage within the hydrogel. Thermogravimetric analysis showed an increase in the stability of hydrogel either having high AA ratio or high crosslinker ratio. The swelling of the hydrogels was carried out by investigating the effect of time, pH (buffered and nonbuffered) and ionic media. In non-buffered media the overall swelling was found to be high as compared to buffered media. Maximum swelling was observed in hydrogel having mass ratio of 7.0 (AA : CM-chitosan). This hydrogel showed low swelling in low pH similar to that of the stomach and high swelling in neutral pH similar to that of the small intestine and can be used in drug delivery applications

Molecularly-Imprinted Calcium Phosphate/Calcium Alginate Composite Microspheres by Surface Imprinting via Silane Crosslinking

This paper describes the development of a new type of molecularly-imprinted composite microspheres. Composite microspheres of calcium phosphate/calcium alginate (CP/CA CMs) were prepared from calcium phosphate and sodium alginate through the use of calcium chloride (CaCl2) as a gelling agent in an inverse suspension. Molecularly-imprinted calcium phosphate/calcium alginate composite microspheres (CP/CA MICMs) were then prepared by surface imprinting using CP/CA CMs as the supporting matrix, ethylene tri(β-methoxy)ethoxysilane (A-172) and γ-amidopropyltriethoxysilane (KH-550) as the functional monomers and crosslinking agents, respectively, and Methyl Orange as the template in aqueous solution. The CP/CA MICMs and non-imprinted composite microspheres (NICMs) were characterized by Fourier-transform infrared spectroscopy and optical microscopy. The adsorption behaviour of the CP/CA MICMs and NICMs were determined by ultraviolet spectrophotometry. The results indicated that molecular imprinting occurs via the crosslinking of silanes on the surface of the CP/CA CMs, and that CP/CA MICMs possess an adsorption capacity which exhibits greater selectivity. A schematic representation of the imprinting and recognition process of CA/CP MICMs by surface imprinting via silane crosslinking was presented.