Recycling of Commercial E-glass Reinforced Thermoset Composites via Two Temperature Step Pyrolysis to Improve Recovered Fiber Tensile Strength and Failure Strain

Ryan S Ginder,Soydan Ozcan

doi:10.3390/recycling4020024

Ryan S Ginder, Soydan Ozcan

Open Access

https://doi.org/10.3390/recycling4020024

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Abstract

Economic and regulatory pressures on the global composites industry have encouraged the research and development of technology for the recycling of fiber reinforced polymer composites. Although significant advancements have been made in the recycling of carbon fiber composites, more progress is needed in the recovery of glass fibers, which make up the overwhelming volume of the composites market. In this study, wind turbine blades and automotive sheet moulding compound (SMC) were subjected to a two temperature step pyrolysis. This multistep process yielded improvements in the recovered E-glass fiber’s tensile strength, by as much as 19%, and strain to failure, by as much as 43%, over a single high temperature step pyrolysis. Despite these gains, pre-pyrolysis fiber measurements indicate that pre-existing damage may inherently limit the quality of glass fiber recoverable from pyrolysis without any post processing.

Highlights

Introduction70% of these composites are made with thermosets [1]
Over 9 million tons of glass fiber reinforced polymer composites were produced globally in 2015 [1].Roughly 70% of these composites are made with thermosets [1]
As pyrolysis cannot recover fiber strength that the input material did not possess, these results suggest that pre-existing fiber damage may be more of a limiting factor in the recycling of glass fiber composites than damage introduced during fiber reclamation

Summary

Introduction

70% of these composites are made with thermosets [1] As such, they are quite resilient in service but do not lend themselves towards recycling like other engineering materials (e.g., metals and thermoplastics). In a low or no oxygen environment, composite scrap is heated to thermally break down the resin phase, resulting in recovered fibers, fillers, char, and hydrocarbon gases and oils [2]. This process has proved fairly successful in the recovery of carbon fiber through a variety of reactor designs and has reached the point that commercial quantities are becoming available on the open market [3,4,5]. The resulting hydrocarbon gases can contain significant portions of hydrogen, methane, carbon monoxide, and carbon dioxide, while the resulting oils tend to be rich in aromatic compounds; exact compositions can be quite complex and vary with different resin mixtures, additives, temperatures, and atmospheric compositions [2]

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