Glass fibre sizing, a critical thin coating applied during glass fibre manufacturing, significantly influences the quality and performance of the final composite products. This sizing is integral not only to the fibre's processability and profitability but also to optimizing the fibre/matrix interface in composites. Recognizing the necessity to enhance our understanding of fibre sizing and its impact on this interface, this thesis aims to provide a thorough study of the glass fibre thermoplastic interface, focusing on the role of different sizing components in the interphase performance of glass fibre-reinforced thermoplastics.
A pivotal aspect of this study is the development of a novel laboratory-based coating method, using the spin coating technique, designed to closely mimic the properties of industrial sized fibres. This method was assessed against traditional dip coating for the lab research and industrial sizing techniques, examining variables such as Loss of ignition (LOI), surface chemistry, adhesion, and surface morphology. Findings indicate that spin coating not only achieves an LOI% similar to industrial standards but also allows for precise control over LOI% by adjusting the spinning speed. This method yields a thin coating layer, crucial for achieving the desired thicknesses. The research evaluates the efficacy of silane variations, i.e., γ-aminopropyltriethoxysilane (APS), γ-glycidoxypropyltrimethoxysilane (GPS), and γ-methacryloxypropyltrimethoxysilane (MPS), in the performance of glass fibre-reinforced thermoplastics. The interfacial shear strength (IFSS) of fibres sized with different components was measured using microbond tests with thermoplastics like Homo-Polypropylene (PP), Maleic Anhydride Grafted Polypropylene (MAPP), Polyamide 6 (PA6), and Polybutylene Terephthalate (PBT). The study also investigates the impact of pH levels and APS solution concentrations (as the most compatible silane for thermoplastics [1]) on IFSS. Results demonstrate a general increase in IFSS with APS sizing across the studied matrix systems, though pH level variations showed minimal impact. The PP-compatible sizing was selected for investigation, as PP is one of the most widely used thermoplastics due to its excellent corrosion resistance, ease of processing, and low cost [2]. The effect of the PP film-former and full-sizing (PP film former + APS) was also examined to understand the interfacial properties of the sized
fibre with PP and MAPP matrices. The study revealed that using the film former alone does not enhance the IFSS in comparison to the bare fibre. Nonetheless, a combination of silane and the film former leads to an increase in IFSS for both PP and MAPP matrices. In summary, this thesis provides a comprehensive exploration of glass fibre thermoplastic
interfaces, emphasizing the critical role of sizing in optimizing stress-transfer capability and overall performance in glass fibre-reinforced thermoplastics. The findings highlight the spin coating technique's potential in laboratory research and the pivotal role of silane coupling agents and film former in fibre sizing, setting the stage for developing more realistic sizing in the laboratory and providing efficient and effective sizing formulations for advanced composite materials.
| Date of Award | 18 Nov 2024 |
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| Original language | English |
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| Awarding Institution | - University Of Strathclyde
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| Sponsors | University of Strathclyde |
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| Supervisor | Liu Yang (Supervisor) & James Thomason (Supervisor) |
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