FTIR study of poly(propylene carbonate)/bisphenol A blends

A systematic investigation by FTIR spectroscopy was undertaken on blends of poly(propylene carbonate) (PPC) and bisphenol A (BPA). It provided direct evidence of the hydrogen bond (H‐bond) between BPA O? H groups and PPC C?O groups. Using a curve‐fitting method, qualitative as well as quantitative information concerning this H‐bond interaction was obtained. The inter‐H‐bond in PPC/BPA blends was weaker than the self‐H‐bond in BPA. The absorptivities of the free and the H‐bonded C?O groups were nearly equal. The fraction of H‐bonded C?O in the blends increased with BPA content and leveled off at a value close to 40 %. Finally, FTIR–temperature measurements of pure PPC and a representative blend were reported: by monitoring the peak areas of C?O absorptions, the dissociation of the inter‐H‐bonds and the thermal degradation of PPC were observed. It revealed that the presence of BPA clearly retarded the thermal degradation of PPC. Copyright © 2004 Society of Chemical Industry     

Study of miscibility of melamine-formaldehyde resin and poly(vinyl acetate) blends for use as adhesives in engineered flooring

The objective of this research was to investigate the miscibility behavior of melamine-formaldehyde (MF) resin and poly(vinyl acetate) (PVAc) blends for their use as adhesives for bonding fancy veneer and plywood in engineered flooring, by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). Blends of various compositions of MF resin/PVAc were prepared. To determine and compare the effect of PVAc content, blends with PVAc to MF resin weight ratios of 0, 30, 50, 70 and 100% were prepared. These blends displayed a single cure temperature over the entire range of compositions indicating that this blend system was miscible in the amorphous phase due to the formation of hydrogen bonding between the amine groups of the MF resin and the carbonyl groups of PVAc.     

Structure of silane layer formed on silica particle surfaces by treatment with silane coupling agents having various functional groups

The surface treatment of spherical silica particles with silane coupling agents having various organic functional groups was conducted and the effect of the alkoxy group number on the molecular flexibility of the silane chain with multilayer coverage was investigated using ¹H-pulse nuclear magnetic resonance spectroscopy. The silica particles were treated with 2-propanol solution and heated at 120?°C for 24?h after solvent evaporation to accelerate the polycondensation reaction of silanol groups. For multilayer coverage, flexible linear chain and rigid network structures were expected to form on the surface from the di- and trialkoxy structures, respectively. However, the rigid network structure was formed from both the di- and trialkoxy structures with glycidoxy, amino, and methacryloxy functional silanes. Ring opening of the epoxy group occurred, followed by reaction to form the network structure, even with the dialkoxy structure of the glycidoxy functionality. Ring opening of the epoxy group could be reduced by pH adjustment of the treatment solution and the linear chain structure was formed from the dialkoxy structure. In the case of amino and methacryloxy functional groups, hydrogen bonds were formed between the amino or methacryloxy groups and the silanol groups on the silica surface or silane molecules.     

表面硅烷预处理/环氧镁铝复合涂层体系对铝合金的保护性能

在LY12铝合金表面制备了一层硅烷膜,研究了硅烷膜对铝合金表面富镁铝环氧涂层性能的影响。硅烷处理后,形成了硅烷膜与基体之间Si-O-Al共价键以及硅烷膜内部的Si-O-Si 结构,而硅烷膜中未成键的硅醇基团-OH以及R-的环氧基团与涂层中的有机组分反应成键或通过范德华力发生交联互穿,使铝合金基体与环氧镁铝复合涂层之间形成更加牢固的交联互穿网络结构（IPN）,镁铝复合涂层在LY12铝合金基体上的附着力明显提高。马丘测试和电化学阻抗测试结果表明,硅烷处理改善了LY12铝合金表面镁铝复合涂层的整体屏蔽性能,使涂层体系的保护效果显著提高,保护时间延长。     

In situ fourier‐transform infrared spectra analysis of hydrogen bond in polypropylene/chlorinated polypropylene/polyaniline composite

The previous studies suggest that hydrogen bond between chlorinated polypropylene (CPP) and polyaniline (PANI) plays a prominent role in the decision of polypropylene/CPP/PANI composites' electric property. In situ Fourier‐transform infrared spectra were employed to detect and identify the relationship between the hydrogen bond and the temperature. Two kinds of hydrogen bond were carefully studied in the nitrogen–hydrogen bond (N? H) stretching, sulfur–oxygen double bond (S?O) stretching, and carbon–chlorine bond (C? Cl) stretching regions, using an iterative least‐squares computer program to obtain the best fit of spectra. The ratio of absorptivity coefficients and the mole fraction of the “free” and two kinds of H‐bonded N? H were calculated. There exists an apparent turning point in the curves of the relationship between the fraction of two kinds of H‐bonded N? H and temperature. This phenomenon also exists in the S?O stretching region, and the turning point is at about 60°C. The mole fraction of H‐bonded C? Cl decreases, and that of “free” C? Cl increases with increasing temperature. The enthalpy gap between the H‐bonded N? H…O?S and the H‐bonded N? H…Cl?C dissociation was also obtained as 23.2 KJ/mol. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Adhesion promotion of poly(phenylene sulfide) to aluminum treated with silane coupling agents

This work seeks a suitable silane coupling agent for the bonding of poly(phenylene sulfide) (PPS) to aluminum surfaces. Candidate silanes are selected on the basis of the thermodynamic compatibility of the organofunctional group of the silane with the polymer, as expressed by the (negative) Gibbs free energy of mixing for equimolar pseudo-solutions of the organofunctional group of the silane and the repeat units of the polymer, (?ΔG ^m _0.5). The latter is calculated using the group contribution modified UNIFAC (Dortmund) method. Samples prepared with polymer bonded to silane-modified aluminum surfaces are investigated using a 90-degree peel test. An aromatic sulfide silane is predicted both to yield optimum compatibility with the polymer and is found to produce a 12-fold enhancement of adhesion (the maximum among the systems tested) over the case in which the aluminum substrate was untreated. The extent of the correlation between the compatibility parameter and the measured practical adhesion, however, is limited by several factors, including the unavailability of a wide range of candidate silanes and the incompleteness of the current UNIFAC parameter database.     

Miscibility and hydrogen bonding in blends of poly(vinyl acetate) with phenolic resin

The miscibility of phenolic resin and poly(vinyl acetate) (PVAc) blends was investigated by differential scanning calorimeter (DSC), Fourier transform infrared spectroscopy (FT-IR) and solid state ¹³C nuclear magnetic resonance (NMR). This blend displays single glass transition temperature (T_g) over entire compositions indicating that this blend system is miscible in the amorphous phase due to the formation of hydrogen bonding between hydroxyl groups of phenolic resin and carbonyl groups of PVAc. Quantitative measurements on fraction of hydrogen-bonded carbonyl group using both ¹³C solid-state NMR and FT-IR analyses result in good agreement between these two spectroscopic techniques. According to the proton spin-lattice relaxation time in the rotating frame (T_1ρ^H), the phenolic/PVAc blend is intimately mixed on a scale less than 2-3 nm. Furthermore, the inter-association equilibrium constant and its related enthalpy of phenolic/PVAc blends were determined as a function of temperatures by infrared spectra based on the Painter-Coleman association model.     

The adhesion promotion mechanism of organofunctional silanes

The adhesion promotion mechanism of organofunctional silanes has historically been attributed to the formation of an “interpenetrating polymer network” between a polymerized silane film and the polymer. This notion was investigated by formulating and testing two hypotheses. First, if the adhesion promotion is due to the formation of an interpenetrating polymer network, variation in the time-temperature profile of the bonding conditions should alter the extent of interdiffusion and thus interfacial strength. Second, if the adhesion promotion is due to compatibility and penetration of the silane organofunctional group, not the bulk silane film, variation in the structure of that group should change interfacial strength. Direct interfacial strength measurements using single-particle composites show that variation in the time-temperature profile of bond formation does not significantly affect interfacial strength. However, use of a series of aminofunctional silanes (with constant C : N ratio and identical surface energetics) revealed a relationship between length of the aminofunctional group and interfacial strength. These results suggest that the adhesion promotion for the system studied is controlled by compatibility and penetration of the silane organofunctional group. Whereas all of the interfaces studied here featured poly(vinyl butyral), the conclusions should apply to all amorphous polymeric materials. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1025–1033, 1998     

Miscibility enhancement on the immiscible binary blend of poly(vinyl acetate) and poly(vinyl pyrrolidone) with bisphenol A

The miscibility behavior and hydrogen bonding of ternary blends of bisphenol A (BPA)/poly(vinyl acetate) (PVAc)/poly(vinyl pyrrolidone) (PVP) were investigated by using differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). The BPA is miscible with both PVAc and PVP based on the observed single T_g over the entire composition range. FTIR was used to study the hydrogen-bonding interaction between the hydroxyl group of BPA and the carbonyl group of PVAc and PVP at various compositions. Furthermore, the addition of BPA is able to enhance the miscibility of the immiscible PVAc/PVP binary blend and eventually transforms into miscible blend with single T_g, when a sufficiently quantity of the BPA is present due to the significant Δχ and the ΔK effect.     

Multinuclear 1D- and 2D-NMR study of the hydrolysis and condensation of bis-1,2-(triethoxysilyl)ethane

This paper focuses on the study of the effect of aging on the composition of the solutions used for deposition of silane films onto metals. Such films are used for corrosion protection and adhesion applications. The silane films interact with metallic surfaces by reactions between the OH groups of both materials with elimination of water. Therefore, prior to the immersion of the metal into the silane solution, the silane has to be hydrolysed in order to generate a maximum of silanol (SiOH) groups, while minimizing condensation leading to siloxane (SiOSi) groups. One of the main factors influencing the amounts of silanol and siloxane groups produced is the solution aging. This paper demonstrates by NMR spectroscopy that in the case of a bridged silane, namely bis-1,2-(triethoxysilyl)ethane, a stable plateau offering a good compromise between hydrolysis and condensation in the solution is obtained between 24 h and a few days of aging.     

Crosslinking reactions during processing of silane modified polyethylenes

A study of the crosslinking reactions in silane modified polyethylenes has been completed. Crosslinking of ethylene-vinyl trimethoxy silane copolymers during high temperature melt processing has been investigated using melt rheological and infrared spectroscopic techniques. Two environmental factors are shown to influence crosslinking formation, namely oxidation of the polymer and the presence of di-n-butyl-tin dilaurate, a condensation catalyst. These are believed to initiate high temperature crosslink formation via different non-interacting mechanisms. It is deduced that silane crosslink formation as a result of oxidation is due to intramolecular interaction of oxidised polyethylene and pendant methoxy silane branches. Observation of a hydrogen bonded silanol intermediate species is consistent with this hypothesis.     

Effect of the grafted silane on the dispersion and orientation of clay in polyethylene nanocomposites

The CTAB ammonium intercalated montmorillonite clay, CMT, was modified by an alkylsilane, Dodecyltrimethoxylsilane, to improve the miscibility of organoclays with PE matrix, involving the grafting reaction between the silane and silanol groups on the edge of clay. The silane modified clays (DMT) exhibited improved thermal stability due to the replacement of the physically adsorbed ammonium by the covalently bonded silane. The clays were melt compounded with polyethylene. Compared with the composite of PE/CMT, the clay dispersion state was improved, and a unique orientation of the clay layered was observed in PE/DMT nanocomposites, which was confirmed by XRD and TEM studies. The dispersion state, orientation degree of clay and, as a result, the mechanical and thermal properties of the nanocomposites were enhanced with the increasing amount of the grafted silane, indicating that the edge grafting of silane played a crucial role in controlling the structure and properties of nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

The structure of aminofunctional silane coupling agents: 1. γ-Aminopropyltriethoxysilane and its analogues

Gamma-aminopropyltriethoxysilane (γ-APS) and its analogues are studied as aqueous solutions as well as solids by Fourier transform infra-red spectroscopy (FT i.r.) and laser Raman spectroscopy. Emphasis was placed on a determination of the nature of the interaction between the amine groups and the residual silanol groups in partially cured solids. Comparison with γ-aminopropyltrisilanolate and partially cured solids obtained from γ-aminopropylmethyldiethoxysilane and γ-aminopropyldimethylethoxysilane lead us to conclude that the residual silanol groups are strongly hydrogen bonded to the amine groups as SiOH … NH₂ rather than SiO^? … ⁺NH₃. Hydrolysis of γ-APS at concentrations ranging 2–80% by weight showed that the solutions below 40% by weight have a few unhydrolysed alkoxy groups. The amine groups are mutually hydrogen bonded in unhydrolysed silane. However, in an aqueous solution and highly cured solids, the amine groups are either free or are interacting predominantly with water molecules.     

Synthesis and properties of hydroxyapatite nanorod‐reinforced polyamide 6 nanocomposites

BACKGROUND: Polyamide 6 (PA6)/hydroxyapatite (HA) nanocomposites, which combine the bioactivity and biocompatibility of HA and the excellent mechanical performance of PA6, have emerged as new biomaterials with potential applications in the clinical setting. It has been shown that these nanocomposites show good similarity to natural bone in terms of chemistry and mechanical properties. RESULTS: In this study, highly crystallized hydroxyapatite nanorods (HANR) were used to fabricate PA6/HA nanocomposites via in situ hydrolytic ring‐opening polymerization of ε‐caprolactam. The effect of the HANR on the thermal stability, crystallization behavior and hydrogen bonding of PA6 was investigated using thermogravimetric analysis, differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy, respectively. It was found that HANR can obviously increase the crystallization temperature and decrease the degree of supercooling. In addition, the thermal degeneration temperature of PA6 is also increased by the incorporation of HANR. FTIR analysis of the hydrogen bonded N? H stretching vibration revealed that, with increasing HANR loading, the hydrogen bonded N? H stretching band shifts to higher frequency and decreases in intensity. CONCLUSION: The thermal stability and crystallization ability of PA6 are improved considerably by the incorporation of HANR. However, the hydrogen bonding strength is weakened and the degree of ordering of hydrogen bonding is reduced by the incorporation of HANR, which can be explained by the formation of hydrogen bonds at the interface between ? OH groups of HANR and the ? N? H or ? C?O groups of PA6. Copyright © 2009 Society of Chemical Industry     

Surface structure of silane-treated glass beads and its influence on the mechanical properties of filled composites

The surface treatment of glass beads, chosen as a model filler, was carried out using four different silane coupling agents with multilayer coverage. For this purpose, silanes having an aminopropyl or a methacryloxypropyl group as an organofunctional group with di- or tri-alkoxy structures were used. The amount of silane detected on the bead surface was four to six times that required for a monolayer coverage. The topography of the silane layer on the bead surface was observed using an atomic force microscope. The topography was strongly affected by the composition of the silane solution and the number of alkoxy groups in the silane. The effects of the organofunctional group and the number of alkoxy groups of the silanes on the mechanical properties of bead-filled poly(vinyl chloride), chosen as a typical ductile polymer, were investigated. A higher yield stress was observed for the silane with an aminopropyl group than for that with a methacryloxypropyl group. Furthermore, for each organofunctional group, the yield stress was higher for the silane with a dialkoxy structure than for that with a trialkoxy structure. However, their effects on the elongation-at-break were contrary to the above tendencies.     

Chemical reactions in the bulk of the epoxy-functional silane hydrolyzate

Chemical reactions in the epoxy-functional silane hydrolyzate bulk have been studied by Fourier transform infrared spectroscopy (FT-IR). It was found that the silanol group opened the epoxy ring upon heating, concurrently with the silanol condensation. The kinetics of these reactions were studied, and the relative reaction rates were obtained.     

The interaction of alkoxy silane coupling agents with silica surfaces

The interactions of γ-aminopropyltriethoxy silane (A-1100), γ-methacryloxytrimethoxy silane (A-174), γ-glycidoxytrimethoxy silane (A-187), and ethyltriethoxy silane (A-15) with silica surfaces have been studied by means of infrared spectroscopy. The results indicate that the major force holding the silane to the silica surface after application from dilute solutions is primary chemical bonding. These bonds are formed by a condensation reaction between silanols on the hydrolyzed form of the silane and hydroxyl groups on the silica surface. In the case of the amino-silane (A-1100), hydrogen bonding was found to exist but was of minor importance in bonding the silane to the surface. In studying the effects of the addition of water, acetic acid, or n-propylamine to various silane treating solutions, it was found that n-propylamine has a unique catalytic effect on the condensation reaction. This catalytic effect explains the observation that γ-aminopropyltriethoxy silane is more reactive than the other silanes studied. It is felt that silanes not containing an amine group can be made more effective if they are applied in the presence of an amine catalyst.     

Specific interactions in miscible polymer blends of poly(2‐hydroxypropyl methacrylate) with polyvinylpyrrolidone

The miscibility behaviour and hydrogen‐bonding interaction in blends of poly(2‐hydroxypropyl methacrylate) (PHPMA) with polyvinylpyrrolidone (PVP) were characterized using differential scanning calorimetry and Fourier‐transform infrared spectra. This polymer blend was miscible over the whole composition range and an unusually large positive deviation of T_g from the linearity rule was observed, indicating strong hydrogen bonding between the hydroxyl group of PHPMA and the carbonyl group of PVP. Infrared spectroscopic analysis provided positive evidence for the intra‐molecular hydrogen bonding of PHPMA and inter‐molecular hydrogen bonding between PHPMA and PVP at various compositions and temperatures. Furthermore, equilibrium constants and enthalpies of self‐association and inter‐association between functional groups in the blend of PHPMA and PVP were calculated to explain the results. Copyright © 2004 Society of Chemical Industry     

Competitive hydrogen bonding mechanisms underlying phase behavior of triple poly(N‐vinyl pyrrolidone)–poly(ethylene glycol)–poly(methacrylic acid‐co‐ethylacrylate) blends

Differential scanning calorimetry (DSC) of triple blends of high molecular weight poly(N‐vinyl pyrrolidone) (PVP) with oligomeric poly(ethylene glycol) (PEG) of molecular weight 400 g/mol and copolymer of methacrylic acid with ethylacrylate (PMAA‐co‐EA) demonstrates partial miscibility of polymer components, which is due to formation of interpolymer hydrogen bonds (reversible crosslinking). Because both PVP and PMAA‐co‐EA are amorphous polymers and PEG exhibits crystalline phase, the DSC examination is informative on the phase state of PEG in the triple blends and reveals a strong competition between PEG and PMAA‐co‐EA for interaction with PVP. The hydrogen bonding in the triple PVP–PEG–PMAA‐co‐EA blends has been established with FTIR Spectroscopy. To evaluate the relative strengths of hydrogen bonded complexes in PVP–PEG–PMAA‐co‐EA blends, quantum‐chemical calculations were performed. According to this analysis, the energy of H‐bonding has been found to diminish in the order: PVP–PMAA‐co‐EA–PEG(OH) > PVP–(OH)PEG(OH)–PVP > PVP–H₂O > PVP–PEG(OH) > PMAA‐co‐EA–PEG(? O? ) > PVP–PMAA‐co‐EA > PMAA‐co‐EA–PEG(OH). Thus, most stable complexes are the triple PVP–PMAA‐co‐EA–PEG(OH) complex and the complex wherein comparatively short PEG chains form simultaneously two hydrogen bonds to PVP carbonyl groups through both terminal OH‐groups, acting as H‐bonding crosslinks between longer PVP backbones. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Adsorption of silane onto cellulose fibers. II. The effect of pH on silane hydrolysis,condensation, and adsorption behavior

The hydrolysis of four alkoxysilane agents, γ‐methacryloxypropyl trimethoxysilane (MPS), γ‐mercaptopropyl trimetoxysilane (MRPS), octyl trimethoxysilane OS), and N‐phenyl‐γ‐aminopropyl trimethoxysilane (PAPS), was carried out in an ethanol/water (80/20) solution under both acid and basic conditions. ¹H, ¹³C, and ²⁹Si NMR spectroscopy were used to provide quantitative analyses of the structural components during hydrolysis and condensation reaction. The analysis revealed that the acid‐catalyzed hydrolysis of silane allows the formation of high amount of silanol groups, reduced the selfcondensation reaction among silanol groups and stabilized the proportion of intermediary hydrolyzed species for several days. However, under basic condition, condensation reactions proceed as soon as the hydrolysis reaction started leading to the rapid consumption of silanol groups through selfcondensation and to the growth of three‐dimensional high molecular structures. The interaction of MPS and MRPS with cellulose fibers and the evolution of their surface properties were then investigated using adsorption isotherms and contact angle measurement. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008