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The presence of a secondary phase between the fibres and the matrix has proved to be a good approach for interphase tailoring for enhanced load transfer. In this regard, an optimization of the low-temperature hydrothermal growth process of ZnO-nanorods on different basalt substrates as a function of different growth times was performed. Scanning electron microscope and X-ray diffraction analysis revealed the best results in terms of homogeneity and uniformity of the ZnO nanostructures for the longest growth time, i.e., 5 h for basalt fabrics and 120 minutes for single basalt fibres. The presence of ZnO nanostructures induced a hydrophobic behaviour with contact angles up to 116° for 4- and 5-h growth processes. Fibre/matrix adhesion was characterized by single fibre pull-out tests, showing a 16% increase in interfacial strength. ZnOs added also photocatalytic properties to basalt fibres, enabling a selective removal of organic pollutant equal to 37%. [ABSTRACT FROM AUTHOR]

Abstract In order to improve the fibre-matrix interaction in carbon fibre reinforced composites the polycarbonate (PC) matrix polymer was modified by the introduction of ethyl-3,5-dihydroxybenzoate as reactive sequences in the polycarbonate backbone. This promising strategy can be considered as an alternative approach to the modification of the carbon fibre surface to control and tailor the adhesion between carbon fibres and polymer matrix. The modification of the polycarbonate demonstrated improved adhesion to carbon fibre in pressed films, which was observed with microscopy-ATR-FTIR and SEM when compared to unmodified polycarbonate. Single fibre pull-out testing subsequently confirmed the improved adhesion, demonstrating higher interfacial shear strenght for the functionalized polycarbonate. [ABSTRACT FROM AUTHOR]

In this paper, we report on the use of amorphous lignin, a waste by-product of the paper industry, for the production of high performance carbon fibers (CF) as precursor with improved thermal stability and thermo-mechanical properties. The precursor was prepared by blending of lignin with polyacrylonitrile (PAN), which was previously dissolved in an ionic liquid. The fibers thus produced offered very high thermal stability as compared with the fiber consisting of pure PAN. The molecular compatibility, miscibility, and thermal stability of the system were studied by means of shear rheological measurements. The achieved mechanical properties were found to be related to the temperature-dependent relaxation time (consistence parameter) of the spinning dope and the diffusion kinetics of the ionic liquids from the fibers into the coagulation bath. Furthermore, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical tests (DMA) were utilized to understand in-depth the thermal and the stabilization kinetics of the developed fibers and the impact of lignin on the stabilization process of the fibers. Low molecular weight lignin increased the thermally induced physical shrinkage, suggesting disturbing effects on the semi-crystalline domains of the PAN matrix, and suppressed the chemically induced shrinkage of the fibers. The knowledge gained throughout the present paper allows summarizing a novel avenue to develop lignin-based CF designed with adjusted thermal stability. [ABSTRACT FROM AUTHOR]

In this paper, the oxy-fluorination process and the influence of different concentrations of fluorine and oxygen in the gas phase on the physicochemical properties of polyacrylonitrile(PAN)-based carbon fibers are described. The properties of the treated carbon structures are determined by zeta potential and tensiometry measurements. In addition, changes in surface composition and morphology are investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Adhesion properties are characterized by the single fiber pull-out (SFPO) test. Furthermore, changes in intrinsic properties are described by means of tensile and density measurements. After a primary desizing effect by oxy-fluorination, an increased number of oxygen-containing surface functional groups could be detected, which led to more debonding work in SFPOs with an epoxy-based matrix. It was also shown that the polar surface energy grows with rising fluorine concentration in the reaction gas mixture. In addition, a minor increase of ~10% in the maximum strength of PAN-based carbon fibers is detected by single fiber tensile measurements after oxy-fluorination with a fluorine content of 5% in the reaction mixture. [ABSTRACT FROM AUTHOR]

To achieve good mechanical properties of carbon fibre-reinforced polycarbonate composites, the fibre-matrix adhesion must be dialled to an optimum level. The electrolytic surface treatment of carbon fibres during their production is one of the possible means of adapting the surface characteristics of the fibres. The production of a range of tailored fibres with varying surface treatments (adjusting the current, potential, and conductivity) was followed by contact angle, inverse gas chromatography and X-ray photoelectron spectroscopy measurements, which revealed a significant increase in polarity and hydroxyl, carboxyl, and nitrile groups on the fibre surface. Accordingly, an increase in the fibre-matrix interaction indicated by a higher interfacial shear strength was observed with the single fibre pull-out force-displacement curves. The statistical analysis identified the correlation between the process settings, fibre surface characteristics, and the performance of the fibres during single fibre pull-out testing. [ABSTRACT FROM AUTHOR]

The surface of carbon fibre was rapidly modified by reductive electrochemical deposition employing a range of diazonium salts. Three sets of fibre were generated possessing pendant amine, carboxylic acid, and lipophilic amide ( N -hexyl amide) groups and the effect of these surface chemistries on interfacial shear strength (IFSS) was examined in epoxy resins. Surface grafting of the fibres was studied by X-ray photoelectron spectroscopy, and physical characterisation of the modified fibres showed that our treatments had no detrimental effects on Young's modulus and tensile strength. IFSS increases of 172% and 30% (relative to control fibres) were observed for the amine and lipophilic amide functionalised, respectively. Molecular dynamics simulations of the lipophilic amide suggests IFSS enhancement via soft-soft interactions. Surprisingly, the IFSS of fibres that exhibited carboxylic acid groups at the surface were indistinguishable from that of the untreated control fibres. When applied to polypropylene grafted with maleic anhydride, the amine grafted fibres showed a 67% increase relative to control fibres, attributed to covalent cross-linking between the fibre and maleic anhydride co-monomer. [ABSTRACT FROM AUTHOR]