The composites materials industry is currently experiencing a period of intense growth in new application development due to the potential which light-weight high performance composite materials have to reduce the carbon footprint of many industries. Composite materials have been highly successful in such applications due to the synergy of combining two, or more, dissimilar materials to obtain a better performance than the sum of the individual components. Glass fibre has been particularly successful as the reinforcement in these composites. Today glass fibre products account for more than 95% of fibre reinforcements used in the composites industry, primarily due to their highly attractive performance to price ratio. Possibly the most critical component involved in the manufacture of glass fibres and their composites is the fibre sizing. Sizing is a thin surface coating of mainly organic materials applied to nearly all types of man-made fibres during their manufacture. Given the well-recognized critical importance of sizing in all aspects of the profitability, processibility and performance of glass reinforced composites and consequently to the ultimate success of the composites industry, it is surprising (perhaps even astonishing) to note the lack of a proportionally sized body of fundamental and applied research publications on this subject. There can be few examples of such a large materials industry (global annual production well in excess of 10 million tons of fibre reinforced composites) where the manufacturing and performance of those materials are so critically dependent on such a small component that is so narrowly understood. The research and development of glass fibre sizing is inextricably linked to the intellectual property concerns of glass fibre manufacturers and consequently information on the nature of the technical challenges facing sizing developers is not openly available to the technical community.
Despite these challenges there has been quite some work published in and around the subject of glass fibre sizings over the years. Given the importance of sizings to the continuing success and growth of the composites industry this review has collected and summarized a large proportion of the widely dispersed literature which is openly available around glass fibre sizings. The review should beneficial to academic researchers embarking on, or already working on, fundamental research in the area of glass fibre sizings and interfaces in glass reinforced composites. However, industrial readers from the composite materials supply chain and those engaged with end-use applications using glass reinforced polymers should also find the contents highly useful in improving their insight and understanding of this critical aspect of composite materials.