Y.D. Huang

Synthetic routes, properties and future applications of polymer-layered silicate nanocomposites

This paper focuses on polymer nanocomposites and their syntheses, properties and future applications, several of these application will be successful in the near future. This new type of materials, based on smectite clays usually rendered hydrophobic through ionic exchange of the sodium interlayer cation with an onium cation, may be prepared via various synthetic routes comprising exfoliation adsorption, in-situ intercalative polymerization and melt intercalation. The whole range of polymer matrices covered, i.e., thermoplastics, thermosets and elastomers. Small addition—typically less than 6 wt%—of these nanoscale inorganic fillers promote concurrently several properties of the polymer materials, including tensile characteristics, heat distortion temperature, scratch resistance, gas permeability resistance, and flame retardancy.

The uniform treatment of carbon fiber surface in three-directional orthogonal fabric by oxygen-plasma

An oxygen-plasma treatment of carbon fibre surface in three-directional orthogonal fabric preforms was investigated in this paper. The effects of this treatment on the surface wettability and chemical components of the fibres in both the interior and surface regions of the fabrics were analyzed by using dynamic capillary method and X-ray photoelectron spectroscopy (XPS), respectively. A microdebonding method was employed to determine the uniformity of interfacial shear strength between the fibre and matrix in different regions of the carbon fabric-phenolic composites, and the flexural strength was also tested to evaluate the effects of the treatment. The results indicated that, the oxygen-plasma significantly improved the interfacial adhesion by etching, activating the surface of the fibres, and generating the oxygenic functional groups. However, for the fibres in different regions of the fabric, the degrees of the treatment were different, and a longer treatment time was needed to get the relative uniform effect through the fabric. Meanwhile, the loss of tensile property of the fibre due to treatment was investigated and found to be small in the range of useful treatments.

Surface Characteristics of Rare Earth Treated Carbon Fibers and Interfacial Properties of Composites

Abstract Effect of rare earth treatment on surface physicochemical properties of carbon fibers and interfacial properties of carbon fiber/epoxy composites was investigated, and the interfacial adhesion mechanism of treated carbon fiber/epoxy composite was analyzed. It was found that rare earth treatment led to an increase of fiber surface roughness, improvement of oxygen-containing groups, and introduction of rare earth element on the carbon fiber surface. As a result, coordination linkages between fibers and rare earth, and between rare earth and resin matrix were formed separately, thereby the interlaminar shear strength (ILSS) of composites increased, which indicated the improvement of the interfacial adhesion between fibers and matrix resin resulting from the increase of carboxyl and carbonyl.

Solvent-dependent adsorption of phenolic resin onto silica substrate

The solution impregnation route is commonly exploited to prepare polymer-based composites. However, the adsorption of polymer components is complicated, which is the result of interactions between reinforcement, solvent and polymer. In this study, the adsorption of phenolic resin onto silica substrate from different solvents was investigated by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, UV-visible absorption spectroscopy and thermogravimetric analysis (TGA). Isotherms for phenolic resin adsorption from solvents onto silica substrate have been examined as a function of phenolic resin content in different solvents. The viscosity and surface tension were measured for the solution systems before and after adsorption. Hydrogen bonding interaction was considered to be operative in the resin–solvent–silica system. The adsorption of phenolic resin is dependent on its relative affinity for the solvent on one hand and for the silica surface on the other. UV-visible absorption spectroscopy results suggested that phenolic resin forms hydrogen bonds with the solvent, which competes with the hydrogen-bonding adsorption mechanism for phenolic resin occurring on silica surface. This hydrogen bonding in solution along with the competitive adsorption of solvent onto silica surface suppresses the adsorption of phenolic resin and such suppression is unfavorable in a solution impregnation process.

Effects of Coating Structures on Interfacial Properties of Carbon Fibre/Polyarylacetylene Composites

Carbon fibres (CF) were modified with different coatings, including vinyltrimethoxysilane (VMS) and vinyl-silsesquioxane (VMS-SSO). VMS-SSO was obtained by the sol-gel hydrolytic condensation of VMS. The structure of VMS-SSO was characterised by FT-IR, NMR (1H, 13C and 29Si) and UV-MALDI-TOF MS. The VMS-SSO included several structures such as cage, semi-cage and ladder. Interlaminar shear strength (ILSS) and interfacial shear strength (IFSS) were measured to evaluate the effects of the coating structure on the interfacial properties of carbon fibre/polyarylacetylene (CF/PAA) composites. The ILSS and IFSS of CF/PAA composites treated with VMS and VMS-SSO coatings showed that VMS-SSO coating had a better treatment effect than VMS. The fracture surface of the CF/PAA composites treated with different coatings was observed by SEM. The complex structures of the VMS-SSO seem to be the main reason for the different degrees of improvement in the interfacial adhesion.

AFM characterization of interphase properties of silver-coated carbon fibre reinforced epoxy composites

Carbon fibre (CF) surfaces were silver-coated using an electroless deposition technique. Atomic force microscopy (AFM) was used to measure the topography and roughness of the silver-coated carbon fibre surfaces after various deposition times before forming a composite. The height images showed that the surface coverage of silver (Ag) islets after 2 min was the most complete and uniform. AFM in the force modulation mode probed the local mechanical properties within the interphase regions in a CF/epoxy composite system. The results showed that the stiffness of the Ag coating was similar to that of the carbon fibres, and higher than that of the epoxy matrix. The interphase thickness varied from 50 nm to 200 nm, depending on the silver deposition time. The interphase morphology revealed the interaction mechanisms between the silver layers and the carbon fibres. The interfacial adhesion properties were evaluated by microbond testing. The interfacial shear strengths (IFSS) of the microcomposites were improved after Ag plating. Due to the increase in roughness and the small volume of the Ag particles compared with the epoxy resin, the Ag plating layers promoted mechanical interlocking between the carbon fibres and the epoxy resin. At a deposition time of 2 min, the maximum IFSS was 36.2 MPa, 17.9% higher than that of the uncoated specimens.

Surface Modification of PBO Fibres by Gamma-Ray Irradiation: Effects on Interfacial Properties of their Epoxy Composites

The surfaces of poly [p-phenylene benzobisoxazole] (PBO) fibres were grafted with epichlorohydrin by a gamma (γ)-ray irradiation method. The influence of irrdiation dose on the interfacial shear strength (IFSS), interlaminar shear strength (ILSS) and the fibre wettability were investigated. In addition, the fibre surface composition, and the shear fracture topography of PBO fibre/epoxy resin composites were analysed by X–ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The results indicate that a dose of 30KGy was the optimal condition for PBO fibre surface modification. The oxygen content of the irradiated PBO fibres was 22% higher than that of the untreated ones, and chlorine atoms were introduced onto the surface of the fibres through grafting actions between epichlorohydrin and PBO. The wettability of the epichlorohydrin-grafted PBO fibres was significantly increased, and the values of IFSS and ILSS of its composites were increased by 70% and 135%, respectively. SEM shows that the improved interfacial adhesion resulted in a change in the failure mode of PBO fibre/epoxy composite from an adhesive-type interfacial failure to a cohesive-like matrix failure.

Influence of Silsesquioxane Coatings on Interfacial and Impact Properties of Carbon Fiber—Polyarylacetylene Composites

A carbon fiber surface is treated with silsesquioxane (SSO) coatings, including methyl-SSO (MES-SSO), vinyl-SSO (VMS-SSO), and 3-(methacryloxy) propyl-SSO (MPMS-SSO). The mechanical behavior of the carbon fiber—polyarylacetylene (CF—PAA) composites is studied in terms of force modulation mode atomic force microscope (AFM), short-beam bending, microdebonding, and impact tests. A transitional layer appears between the fiber and resin after the carbon fibers are treated with SSO coating. Based on experimental results, The authors conclude that the mechanical interfacial properties of the composites, i.e., interlaminar shear strength (ILSS) and interfacial shear strength (IFSS), are largely increased by the SSO coatings on the fiber surface. Impact properties of the composites are also dominated by SSO coatings. These results could be explained as probably due to the effect of SSO coatings, resulting in improved ductile fracture properties, thereby increasing the resistance to deformation and crack initiation of the polyarylacetylene system.

Application of near infrared spectroscopy to control the protective reaction in the synthesis of emamectin benzoate.

A near infrared (NIR) method was developed for the control of the protective reaction in the synthesis of emamectin benzoate. A NIR spectrometer with a fibre-optic probe was used to analyse the residual content of avermectin and the by-product content of the shield. Partial least squares regression was used to develop the calibration models, which for the residual content were preprocessed by second derivative and for the by-product content by first derivative and straight-line subtraction preprocessing methods. After optimising the spectral pre-treatment, the coefficient of determination (R2) of the residual content and by-product content were 0.92 and 0.99 and the root mean square errors of calibration were 0.18% and 0.46%, respectively. When the models were used to determine the residual content and by-product content, the root mean square errors of prediction were 0.20% and 0.48%, respectively. These preliminary findings suggest that the NIR method could be used to predict the residual content and by-product content simultaneously and the process could be completed within 2 min without sample destruction. The control of the protective reaction could be adjusted according to the results obtained using the NIR method. The results indicated that information contained in NIR spectra may be useful to control the protective reaction in the synthesis of the emamectin benzoate.

Blends of pre‐irradiated polypropylene powder and syndiotactic 1,2‐polybutadiene: isothermal and nonisothermal crystallisation kinetics

Purpose – The purpose of this paper is to study the isothermal and nonisothermal crystallisation kinetics of pure polypropylene (PP), 1 kGy pre‐irradiated PP and 1 kGy pre‐irradiated PP/syndiotactic 1,2‐polybutadiene (s‐1,2 PB) (90/10) blends by differential scanning calorimetry.Design/methodology/approach – The Avrami equation, modified Avrami equation, Ozawa equation and the treatment by combining the Avrami and Ozawa equation were used to analyse the isothermal and nonisothermal crystallisation of various samples.Findings – The s‐1,2 PB acted as a heterogeneous nucleation agent during the crystallisation of the PP/s‐1,2 PB blends and accelerated the crystallisation rate. The Avrami exponent n of the blends implied that the isothermal crystallisation kinetics of the blends followed a three‐dimensional growth via heterogeneous nucleation. The modified Avrami equation was limited to describe the nonisothermal crystallisation process of pure PP and 1 kGy pre‐irradiated PP, but it was successful for the ble...