Papers by Author: Edith Mäder

Abstract: Surface defects cause the measured tensile strength of glass and other brittle materials significantly lower than their theoretical values. Here, we describe an on-line process to ‘heal’ surface flaws and functionalise surface properties. A nanometer-scale hybrid coating layer based on styrene-butadiene copolymer with mutiwalled carbon nanotubes (MWCNTs) and/or nanoclays, as mechanical enhancement and environmental barrier layer, is applied to alkali-resistant glass fibres (ARG). The nanostructured and functionalised traditional glass fibres with low fraction of nanotubes or nanoclay (1 wt% in sizing) show significant improvement in both mechanical properties and environmental corrosion resistance. We introduce a healing efficiency factor and conclude that the coating modulus, thickness and roughness are responsible for the mechanical improvement of fibres. Furthermore, we show that the hybrid coating layer is essential for enhanced interfacial adhesion strength of the glass fibre reinforced cement composites.

Abstract: The high performance of poly p-phenylene-2,6-benzobisoxazole (PBO) fibre in mechanical properties and environmental resistance provides great potential applications as reinforcement fibres for composites. However, poor adhesion between PBO fibre and matrix is found because of the chemically inactive and/or relatively smooth surface of the reinforcement fibre. Here, we report the surface modification of PBO fibres by O2 and NH3 plasma treatments. The surface energy and roughness are increased for both sized and extracted fibres after plasma treatments. The sized fibre shows marginal improvement in interfacial adhesion and no change in fibre tensile strength because of the barrier effect of the sizing layer. For the extracted fibre, the plasma treatments cause reduction in both interfacial adhesion and the tensile strength, which is sensitive to plasma treatment conditions as revealed by a bimodal Weibull statistical distribution analysis. The fibre surface roughness is increased and more surface flaws are induced, which could result in coarse interface structures when the treated fibre surface has no adequate wetting and functional groups.

Abstract: A unique melt spinning equipment for E-glass is compatibly combined with a melt spinning extruder to manufacture commingled yarns. The in-situ commingling enables to combine homogeneously both glass and polypropylene filament arrays in one processing step and without fibre damage compared to commingling by air texturing. Best composite performance is achieved with a sizing for glass fibres consisting of aminosilane and maleic anhydride grafted polypropylene film former, which enable a good strand integrity with the polypropylene yarn. The results of fundamental research on variation of technological processing conditions like diameter ratios, draw ratios, variation of cooling conditions and arrangements of intermingling are reported for glass fibre/polypropylene systems.