Evolution of the interfacial stress transfer ability between a glass fibre and a polypropylene matrix during polymer crystallization

A rigorous evaluation of the influence of a transcrystalline interphase on the adhesion between a fibre and a polymer matrix is difficult because it is generally not possible to consider this parameter without other factors. Indeed, in the case of a reinforcing material allowing spontaneous transcrystallization of a thermoplastic matrix, the inhibition of this phenomenon is, for instance, possible by modifying the surface topography or the physico-chemical nature of the fibre by appropriate coatings. In the same way, the fibres which do not intrinsically favour transcrystalline growth can behave as active substrates by applying a shear stress onto the fibre-matrix interface. In this case, however, processing of the sample for the classical micromechanical tests remains extremely difficult. In order to understand better the participation of a transcrystalline interphase in the interfacial adhesion in a polypropylene–glass fibre system, an experimental protocol has been developed which allows us to evaluate the evolution of the interfacial shear stress during the matrix crystallization, the latter being spherulitic or cylindritic. The results show that a transcrystalline interphase in a polypropylene–glass fibre composite does not significantly alter the adhesion between the two materials after total crystallization of the matrix. Nevertheless, it is shown that an important hooping of the fibre occurs during the development of a transcrystalline superstructure.     

The influence of surface modifications of glass on glass fiber/polyester interphase properties

Unsized glass fibers and planar glass substrates were subjected to low temperature plasma or wet-chemical process to modify the fiber or substrate surface and thus influence the interphase properties of the glass/polyester system. Plasma-polymerized thin films (interlayers) of organosilicon monomers (hexamethyldisiloxane and vinyltriethoxysilane) were deposited in an RF helical coupling plasma system on the glass surface. Commercial silane coupling agent (vinyltriethoxysilane) was coated onto an unmodified glass surface from an aqueous solution. Bonding at the glass/interlayer interface was analyzed by employing a micro-scratch tester together with an optical polarizing microscope for the planar samples. The results revealed that the adhesion bonding could be controlled by plasma process parameters. Scanning electron and atomic force microscopies enabled characterization of the film surface morphology. Chemical composition and chemical structure of prepared interlayers were characterized using X-ray photoelectron and infrared spectroscopies. Microcomposites (macrocomposites) were tested to evaluate the interfacial shear strength (short-beam strength) of the glass fiber/polyester interphase using the microbond test (short-beam shear). Our study indicated that the most efficient interphase could be prepared by plasma polymerization or wet-chemical process using the vinyltriethoxysilane monomer. The short-beam strength was 110% higher than that for untreated fibers in both cases.     

Influence of glass mechanical strengthening on the adhesion properties of poly(vinyl butyral) films to a float glass surface

The effects of various methods of mechanical strengthening of glass on the adhesion properties of poly(vinyl butyral) (PVB) film to a float glass surface were investigated. The mechanisms of the influence of the strengthening processes on the adhesion properties were analyzed. The influence of different types of pretreatment of the glass surface on the adhesion of the polymer films was also considered. It was shown that ion-exchange strengthening followed by treatment with an alkaline water solution provided the best combination of high mechanical strength of glass and good adhesion of the PVB films to the glass surface. Metal-oxide coatings on float glass increased the mechanical strength of glass but decreased the adhesion strength between the polymer and glass. The adhesion of PVB to the metal-oxide layers was determined not only by the chemical composition of the layers, but also by the method of layers formation, the type of glass surface pretreatment, and the nature of the intermediate layer between the metal-oxide layer and the glass surface.     

Stresses and adhesion of thin metallic coatings on oxide substrates

The growth of thin metallic coatings on oxide substrates prepared by vapour deposition of gold or copper on alumina or magnesia was investigated by transmission electron microscopy. The stresses developed during the growth were followed by the bending method. The evolution of stresses is related to the growth mechanisms. The stresses are compressive for discontinuous deposits and change to tensile as the deposit becomes continuous. The compressive stresses are interpreted as due to the increase of the free energy of the metal–oxide system during the growth of metal particles. The tensile stresses result from the deposit lattice mismatch with the substrate. During the growth partial recrystallization and annealing of defects occur which modify the tensile behaviour of continuous coatings. The adhesion of deposits (Au and Cu) on oxide substrates (Al₂O₃ and MgO) was evaluated by the pull-off method as a function of deposition temperature. Au/Al₂O₃, Cu/Al₂O₃ and Au/MgO systems exhibit identical behaviour, while Cu/MgO shows a large dependence on deposition temperature compared to the others. This behaviour is interpreted as due to the formation of chemical bonds between the metal (Cu) and the oxide (MgO), leading to an interfacial oxide.     

Effect of the chemical modification of the precursor of ZrO2 films on the adhesion of organic coatings

ZrO₂ films were deposited on low carbon steel by a sol-gel process as a chemical pretreatment before the application of a polyester paint. The films were obtained by a dip-coating technique using solutions of Zr(OBuⁿ)4 containing complexing agents (acetylacetone or acetic acid). These additives modified the alkoxide at the molecular level, so a new precursor was formed in solution. This new compound shows slower rates of hydrolysis and condensation than Zr(OBuⁿ)4, which allows the stability of solutions and the morphology of the gel to be controlled. Moreover, the length and the temperature of the thermal treatment influence the structure of the gel by reducing the amount of organic residues. The behavior of the films in promoting the adhesion of organic coatings was evaluated by measuring the detachment of the paint from a cross-scratch of samples which had been exposed for different times in a salt fog chamber. Tests using electrochemical impedance spectroscopy were also carried out. According to the results, most of the samples pretreated with zirconia layers showed a good performance, even better than commercial chemical treatments, when acetic acid was used as a modifier of the alkoxide precursors.     

Influence of fluorine source and TiO2 on glass ceramics based on red clay and magnesite

Abstract

Within the Fe₂O₃–BaO–Al₂O₃–SiO₂ glass system, the influence of different fluorine source and TiO₂ on the crystallisation behaviour and thermal expansion characteristics has been investigated. These aluminosilicate glasses, with different nucleation catalysts (TiO₂, AlF₃ and NH₄F), were successfully prepared from Saudi Arabia raw materials (red clay and magnesite). Thermal behaviour, crystalline phases, microstructures, and thermal expansion coefficient were studied by DTA, XRD, SEM techniques, as well as a dilatometer. Spinel, hexacelsian, monocelsian, kinoshitalite, and Ba-osumilite were developed in glass ceramic samples. Spinel was the early phase formed in all glasses; however, with increasing temperature, hexacelsian and kinoshitalite were developed in fluorine free glasses and fluorine containing glasses respectively. Ba-osumilite was developed and hexacelsian was converted into monocelsian during lengthy heat treatment at 1150°C. A bulk crystalline microstructure was obtained; however, a microscale structure was observed in fluorine free samples and a homogeneous nanoscale microstructure was developed in fluorine containing samples. The coefficient of thermal expansion (CTE) varied according to the phases and the heat treatment parameters. Development of spinel, hexacelsian and kinoshitalite in glass ceramic samples gave CTE values between 86·44 × 10^?7 and 52·53 × 10^?7°C^?1, whereas crystallisation of Ba-osumilite and monocelsian gave CTE values between 51·29 × 10^?7 and ?7·35 × 10^?7°C^?1.     

Influence of silane coupling agents on the surface energetics of glass fibers and mechanical interfacial properties of glass fiber-reinforced composites

The effect of various silane coupling agents on glass fiber surfaces has been studied in terms of the surface energetics of fibers and the mechanical interfacial properties of composites. γ-Methacryloxypropyltrimethoxysilane (MPS), γ-aminopropyltriethoxysilane (APS), and γ-glycidoxypropyltrimethoxysilane (GPS) were used for the surface treatment of glass fibers. From contact angle measurements based on the wicking rate of a test liquid, it was observed that silane treatment of glass fiber led to an increase in the surface free energy, mainly due to the increase of its specific (or polar) component. Also, for the glass fiber-reinforced unsaturated polyester matrix system, a constant linear relationship was observed in both the interlaminar shear strength (ILSS) and the critical stress intensity factor (K_IC) with the specific component, γ_S ^SP, of the surface free energy. This shows that the hydrogen bonding, which is one of the specific components of the surface free energy, between the glass fibers and coupling agents plays an important role in improving the degree of adhesion at the interfaces of composites.     

FT-IR and XPS studies of polyurethane-urea-imide coatings

A series of polyurethane (PU)-urea-imide coatings were synthesized by a systematic three-step reaction process. Initially isocyanate terminated PU prepolymers were prepared by reacting soft segments such as polyester polyols (prepared from neopentyl glycol, adipic acid, isophathalic acid and trimethylol propane) or polyether polyols (polypropylene glycol-1000) with hard segments such as 2,4-toluene diisocyanate or isophorone diisocyanate with NCO/OH ratio of 2:1. Heterocyclic imide ring into the PU backbone was incorporated by co-polymerization with pyromellitic dianhydride (PMDA) from the excess NCO groups in the PU prepolymer with an NCO/anhydride ratio of 1:0.5 and the surplus NCO content after imidization was moisture cured. PU-urea-imide coatings were also obtained by partial chain extension of the excess NCO groups in the NCO terminated PU-imide copolymers, and the remaining excess NCO groups were completely reacted with atmospheric moisture. The obtained polymers were analyzed with Fourier transform-infrared (FT-IR) and angle resolved X-ray photoelectron spectroscopy (AR-XPS). The type and change in intermolecular H-bonding interaction in the PU-urea-imide films with structural variables was identified by deconvolution of the FT-IR spectra using Origin 6.0 software through Gaussian curve-fitting method. The FT-IR analyses of the PU-urea-imide coating films show dependence of phase separation on the nature of chain extender. Surface characterization data from AR-XPS suggests the dependence of phase segregation behaviour on the nature of the chain extender, which also supports the FT-IR observations.     

Effect of waste glass and zircon on ceramic properties and microstructure of porcelain tiles

Abstract

The possibility of using waste glass as a flux in porcelain tiles without deterioration in mechanical properties has been assessed. Waste glass was added to a typical porcelain tile body, replacing feldspar by up to 15%. Zircon was also added at 5% in partial replacement of quartz. The prepared batches were fired at temperatures of 1160 to 1240°C with 20 min soaking time. Addition of 5% zircon in the presence of 5% waste glass resulted in unusual mechanical and physical characteristics. Further additions of waste glass enhanced vitrification and consequently some surface and mechanical properties, but worsened modulus of rupture (MOR) and toughness. Generally specimens containing zircon had better physicomechanical properties.     

Rheological behavior of anaerobic adhesives: Rheological profile modelling depending on the composition

A study is done on the influence of fumarate-based thickeners on the rheological behavior of low-molecular-weight poly(ethylene glycol) dimethacrylate monomers diluents, often used as major components in the formulation of anaerobic adhesives. These solutions generally showed pseudoplastic behavior. The Cross equation was selected to determine the viscosity vs. shear rate curves, at constant temperature. The final equation relates the viscosity as a function of shear rate and thickener concentration. In addition, the zero shear rate viscosity evolution as a function of the thickener weight fraction was studied, showing that two critical concentrations were present.     

The effects of nanostructure and composition on the hydrophobic properties of solid surfaces

The effects of nanoroughness and chemical composition on the contact and sliding angles on hydrophobic surfaces were studied theoretically and experimentally. A theoretical model based on forces developed at the contact area between a liquid drop and hydrophobic smooth or nanoroughened surface was developed and compared with the existing models, which are based on forces developed at the periphery between the drop and the solid surface. The contact area based model gives rise to an interfacial adhesion strength parameter that better describes the drop-sliding phenomenon. Consequently, relationships were derived describing the dependence between the interfacial adhesion strength of the liquid drop to the surface of a given composition, the mass of the drop, the measured contact angles and the sliding angle. For a given surface chemistry, the sliding angle on a nanometric roughened surface can be predicted based on measurements of contact angles and the sliding angle on the respective smooth surface. Various hydrophobic coatings having different surface nanoroughnesses were prepared and, subsequently, contact angles and sliding angles on them as a function of drop volume were measured. The validity of the proposed model was investigated and compared with the existing models and the proposed model demonstrated good agreement with experimental results.     

电感耦合等离子原子发射光谱(ICP-AES)在玻璃成份分析中的应用

用硫酸 氢氟酸溶解样品,在盐酸介质中用ICPAES法测定玻璃成份中的铁、钙、镁、钠、钾、锂等元素氧化物的百分含量.与传统的化学分析法、分光光度法等相比较,该法操作方便,快速、准确度高.测定结果的相对偏差(RSD)小于5%.     

Influence of TiO2, Cr2O3 and ZrO2 on sintering and machinability of fluorophlogopite glass ceramics

Abstract

The influence of Cr₂O₃, TiO₂ and ZrO₂ on the sintering, crystallisation and machinability of SiO₂–Al₂O₃–MgO–K₂O–B₂O₃–F glasses was investigated. Optimum fluoromica glass ceramic compositions with desirable sintering behaviour and machinability were obtained by addition of titanium and chromium oxides to the base glass. Texture and relative intensity of mica phase I_mica/I_Si were determined by XRD analysis and the particle size distribution of chips was studied by drilling. Microhardness and bending strength were also investigated. The relative intensity of mica phase and microhardness were found to be compatible with the experimental results.     

Effect of annealing on the cohesion,adhesion, and tribological behavior of amorphous silicon-containing diamond-like carbon (Si-DLC) coatings on steel

Amorphous silicon-containing diamond-like carbon (Si-DLC) coatings were deposited by Ar+ ion beam-assisted physical vapor deposition of tetraphenyl-tetramethyl-trisiloxane (704 Dow Corning diffusion pump oil) on AISI 4340 low alloy and 440° C high alloy steel specimens, as well as on thin wafers of the same compositions, in order to evaluate residual stresses within the coatings. During annealing in an argon atmosphere at 200°C for up to 30 min, the residual compressive stress, attributed to hydrogen entrapment during deposition, gradually changed to tensile due to loss of hydrogen, and the rate of stress increase decreased with increasing annealing time. The cohesion and adhesion failure loads of the coatings decreased with annealing time, as did the friction coefficient between the coating and a diamond stylus. The specific wear rate, measured by pin-on-disk tribometry, increased with annealing time. These properties are affected not only by the change in residual stress state during annealing, but most likely also by devitrification and the accompanying grain growth. If these effects are neglected, then the properties may be correlated directly with residual stresses in the coating.     

Influence of different glass fiber sizings on selected mechanical properties of PET/glass composites

The properties of fiber-reinforced plastics are considerably influenced by fiber-matrix interaction. The aim of this study was to investigate the influence of glass fiber surface treatments on the morphology of poly(ethylene terephthalate) (PET) and on selected mechanical properties of unidirectional PET/glass fiber composites. The materials used here were E-glass fibers treated with model sizings including aminosilane as a coupling agent and polyurethane and epoxy resin dispersions as film formers and PET as the matrix. For identification of the degree of crystallinity of the PET matrix, differential scanning calorimetry (DSC) was used. To study the influence of the different sizings on the mechanical properties, the following tests were performed: interlaminar and intralaminar shear tests and a transverse tensile test. Dynamic-mechanical analysis (DMA) was used to characterize the behavior of the composites under dynamical load. The DSC results show that the overall crystallinity and the melting behavior of the PET matrix were hardly influenced by the glass fiber surface treatments used. The various strength properties of the composites are influenced not only by the silane coupling agent, but also by the type of film former. With an epoxy resin dispersion, the mechanical properties were enhanced compared with a polyurethane dispersion. These results were confirmed by characterization of the composites by DMA.     

浅析粉末涂膜的边缘覆盖问题

从改变被涂物外观设计、改进喷涂工艺和调整粉末涂料配方设计三方面着手阐述了粉末涂膜边角覆盖问题的解决方法。     

Effects of the interfacial stress-induced crystallization on the matrix crystalline morphology and the mechanical properties of glass fiber-reinforced high density polyethylene composites

In the melt-mixing process of high density polyethylene (HDPE) and glass fibers (GF), four types of composites with various interfacial bond strength were obtained by adding maleic low molecular weight polyethylene (MPEW) or maleic anhydride (MAH) and initiator, etc. The mechanical properties of these composites and their dependence on the matrix crystalline morphology were investigated by scanning electron microscopy, small-angle light scattering, differential scanning calorimetry, wide-angle X-ray diffraction, and a material universal mechanical testing machine. The occurrence of the interfacial transition regions made of extended-chain crystals around glass fibers was found to be the result of crystallization effects induced by the interfacial stress. The interfacial stress was mainly produced from the matrix shrinkage in the specimen molding process. Under high interfacial bond strength conditions, the forming process of the extended-chain crystals was found to both relax the interfacial stress and at the same time, enhance the interfacial phase modulus and improve the mechanical properties of the composites. Under a 30% glass fiber content condition, the extended-chain crystals formed along the normal direction of glass fiber surfaces connected with each other, fully filled the matrix, and led to a significant increase in the Charpy impact strength of the composites. By contrast, under weak interfacial adhesion, the interfacial stress was released by a dewetting process of the interfacial phase and by the formation of interfacial cracks. Consequently, the interfacial stress did not influence the growth of the spherulites in the matrix and at the same time, the Charpy impact strength of the composite was lower.     

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.     

Structure and property of multicomponent germanate glass containing Y2O3

Abstract

CaO–BaO–Al₂O₃–SiO₂–GeO₂ glasses doped with 0·00–16·67 wt-% Y₂O₃ have been prepared by conventional melt quenching method. The influence of Y₂O₃ addition on the properties and structure of the glasses has been investigated. The results show that, with the introducing of Y₂O₃, the density, glass transition temperature and thermal expansion coefficient of the glass increase but the chemical durability declines. In addition, compared with the glass without Y₂O₃, the bend strength of the glass including 4·76 wt-% Y₂O₃ increased from 54 to 110 Mpa. The possible mechanism is that yttria acts as a network former in the structure and makes the island shape network unit repolymerisation by forming Ge–O–Y bond. The absorption strength caused by hydroxyl vibration decreased up to completely disappearance as the Y₂O₃ content increased continuously. The introducing of yttria in the composition causes the conversion from four coordination to higher coordination germanium, which decreases non-bridge oxygen (NBO) and weakens hydroxyl characteristic absorption.