Composites: Part A 61(2014)201-208 Contents lists available at ScienceDirect campsites Composites: Part A ELSEVIER journalhomepagewww.elsevier.com/locate/compositesa The properties of glass fibres after conditioning at composite recycling Cross Mark temperatures J.L. Thomason, L Yang, R. Meier University of strathclyde, Department of Mechanical and Aerospace Engineering, 75 Montrose Street, Glasgow G1 IX). United Kingdom ARTICLE INFO A BSTRACT Results are presented on E-glass fibr 600°. Thermal 6 December 2013 to 70% strength de dane- coated fibres in revised form 28 February 2014 were relatively stable up to 250C but exhibited a precipitous drop at higher conditioning temperatures. Available online 12 march 2014 Unsized fibres exhibited a linear decrease in strength with increasing conditioning temperature. Little onditioned fibres. A simple analysis of the cumulative fibre strength probability resulted in more useful understanding than the Weibull method. The modulus of both fibre types increased linearly with onditioning temperature. Evidence was found of a slow time-dependent reduction of glass fib E Heat treat storage in an uncontrolled environment The results are discussed in terms of the changes g and bulk glass structure during heat conditioning and the role of the glass fibre water e 2014 Elsevier Ltd. All rights reserved. 1 Introduction to its original state. 7. Consequently, recycled fibres have a very poor performance to cost ratio, and in most cases are considered The disposal of end-of-life composite products in an environ- unsuitable for reprocessing and reuse as a valuable reinforcement mentally friendly manner is one of the most important challenges of composites. a breakthrough in this field could enable suck currently facing the industrial and academic composites commu- recycled glass fibres(gfS)to compete with pristine materials in nity. It is projected that by 2015 the total global production of com- many large volume composite applications. The development of posite materials will significantly exceed 10 million tons which, at an economically viable process for regenerating the properties of d- of-life, will occupy a volume of over 5 million cubic meters. thermally recycled glass fibres would have major technological Glass fibre reinforced composites account for more than 90% of societal, economical, environmental impacts. The reuse of these ll the fibre-reinforced composites currently produced. About materials could result in a huge reduction in the environment. 0% of this volume employs thermosetting matrix materials pro- impact of the glass-fibre and composites industry where the ducing composites(grP) that are difficult to recycle in an efficient replacement of pristine glass fibre products by rgF products would anner. The perspectives on this issue have been recently high- equate to a global reduction in COz production of 400,000 Tons/ lighted due to the accelerating growth in the use of such composite annum from reduced melting energy requirements alone Further materials in transportation and wind energy sectors[1-6.A num- more, such a development would also reduce the need for an ber of processes are available for recycling such composites [1, 7]. annual landfill disposal of 2 million Tons of composites. These f these possible routes, thermal recycling is probably the most developments would clearly be in line with the growing societal echnologically advanced and has been piloted in the UK and and environmental pressure to reduce the use of landfill disposal Denmark. However, nearly all options deliver recycled fibres increase the reuse of valuable raw materials resources, and reduce (which make up approximately 60% by weight of the composites) the release of Coz to the atmosphere that suffer from a lack of cost competitiveness with pristine first- Processing temperatures in the production of glass fibre are sig- pass materials. a key factor in this equation is the huge drop in nificantly higher than GRP recycling temperatures. Nevertheless, the performance of recycled glass fibre(80-90%)in comparison earlier work has indicated that the room temperature tensile strength of glass fibre can be significantly reduced by annealing at temperature as low as 150C[ 8. More recent studies have also ng author.Tel:+4401415482691;fax:+4401415525105. confirmed that room temperature glass fibre strength can be re- ss: james. thomason@strathacuk (L Thomason). ress: Technische Universitat Munchen, D-85748 Garching, German duced by exposure to temperatures in the 300-600C temperature 0.101 1359-835Xo 2014 Elsevier Ltd. All rights reserved.The properties of glass fibres after conditioning at composite recycling temperatures J.L. Thomason ⇑ , L. Yang, R. Meier 1 University of Strathclyde, Department of Mechanical and Aerospace Engineering, 75 Montrose Street, Glasgow G1 1XJ, United Kingdom article info Article history: Received 6 December 2013 Received in revised form 28 February 2014 Accepted 1 March 2014 Available online 12 March 2014 Keywords: A. Glass fibres B. Mechanical properties E. Heat treatment E. Recycling abstract Results are presented on E-glass fibre properties after thermal conditioning up to 600 C. Thermal conditioning led to up to 70% strength degradation. Tensile strength and failure strain of silane-coated fibres were relatively stable up to 250 C but exhibited a precipitous drop at higher conditioning temperatures. Unsized fibres exhibited a linear decrease in strength with increasing conditioning temperature. Little significant strength regeneration was obtained from a range of acid and silane post-treatments of heat conditioned fibres. A simple analysis of the cumulative fibre strength probability resulted in more useful understanding than the Weibull method. The modulus of both fibre types increased linearly with conditioning temperature. Evidence was found of a slow time-dependent reduction of glass fibre modulus during storage in an uncontrolled environment. The results are discussed in terms of the changes in surface coating and bulk glass structure during heat conditioning and the role of the glass fibre water content. 2014 Elsevier Ltd. All rights reserved. 1. Introduction The disposal of end-of-life composite products in an environ￾mentally friendly manner is one of the most important challenges currently facing the industrial and academic composites commu￾nity. It is projected that by 2015 the total global production of com￾posite materials will significantly exceed 10 million tons which, at end-of-life, will occupy a volume of over 5 million cubic meters. Glass fibre reinforced composites account for more than 90% of all the fibre-reinforced composites currently produced. About 60% of this volume employs thermosetting matrix materials pro￾ducing composites (GRP) that are difficult to recycle in an efficient manner. The perspectives on this issue have been recently high￾lighted due to the accelerating growth in the use of such composite materials in transportation and wind energy sectors [1–6]. A num￾ber of processes are available for recycling such composites [1,7]. Of these possible routes, thermal recycling is probably the most technologically advanced and has been piloted in the UK and Denmark. However, nearly all options deliver recycled fibres (which make up approximately 60% by weight of the composites) that suffer from a lack of cost competitiveness with pristine first￾pass materials. A key factor in this equation is the huge drop in the performance of recycled glass fibre (80–90%) in comparison to its original state [1,7]. Consequently, recycled fibres have a very poor performance to cost ratio, and in most cases are considered unsuitable for reprocessing and reuse as a valuable reinforcement of composites. A breakthrough in this field could enable such recycled glass fibres (RGFs) to compete with pristine materials in many large volume composite applications. The development of an economically viable process for regenerating the properties of thermally recycled glass fibres would have major technological, societal, economical, environmental impacts. The reuse of these materials could result in a huge reduction in the environmental impact of the glass-fibre and composites industry where the replacement of pristine glass fibre products by RGF products would equate to a global reduction in CO2 production of 400,000 Tons/ annum from reduced melting energy requirements alone. Further￾more, such a development would also reduce the need for an annual landfill disposal of 2 million Tons of composites. These developments would clearly be in line with the growing societal and environmental pressure to reduce the use of landfill disposal, increase the reuse of valuable raw materials resources, and reduce the release of CO2 to the atmosphere. Processing temperatures in the production of glass fibre are sig￾nificantly higher than GRP recycling temperatures. Nevertheless, earlier work has indicated that the room temperature tensile strength of glass fibre can be significantly reduced by annealing at temperature as low as 150 C [8]. More recent studies have also confirmed that room temperature glass fibre strength can be re￾duced by exposure to temperatures in the 300–600 C temperature http://dx.doi.org/10.1016/j.compositesa.2014.03.001 1359-835X/ 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +44 01415482691; fax: +44 01415525105. E-mail address: james.thomason@strath.ac.uk (J.L. Thomason). 1 Current address: Technische Universität München, D-85748 Garching, Germany. Composites: Part A 61 (2014) 201–208 Contents lists available at ScienceDirect Composites: Part A journal homepage: www.elsevier.com/locate/compositesa