Y. Ma, D. Kim, M-S Wu, L. Bai, X. Gao, B. Qing, J. He, X. Lib, S.R. Nutt, B. Liang
Adesso Advanced Materials Inc.,
Keywords: recycling, processing, thermoset, recyclable resin, carbon fiber composite, vacuum assisted resin transfer molding (VARTM)
Summary:Wind energy has become an increasingly important renewable energy source. In 2015 alone, the U.S. wind industry installed wind turbines generating 8,595 MW, a 77 % increase over 2014 , and the market growth is expected to continue. According to the Global Wind Energy Council (GWEC), since the 1980s, wind turbine blades have increased eight-fold, surpassing 60 meters in length, to harvest more energy as a green solution to meet global energy demand . Such demand and size increases require development of lighter structures, particularly those based on fiber-reinforced polymers (FRPs). The average lifespan of wind turbine blades is 20-25 years. With increased use of FRPs in the wind power industry, within the next 25 years, 225,000 tons per year of FRP-based rotor blades are projected to be eligible for recycling worldwide . Thus, production of future wind turbine blades will require more efficient materials processing, reliable performance, and FRPs that are recyclable. The focus of this project is development of such FRPs, which offer major economic and environmental benefits. In this project, we address these goals by developing and demonstrating a recyclable epoxy resin based on patented ‘cleavable’ curing agents (Adesso)  which can be chemically separated from the fiber reinforcement and subsequently recycled under moderate pressure and temperature to yield small polymers. Thermochemical and thermomechanical properties of a prototype resin system were evaluated to develop in-process cure kinetics and viscosity models. Based on these models, a Vacuum Assisted Resin Transfer Molding (VARTM) process was demonstrated to manufacture lab-scale FRPs. Lastly, the turbine blades will be recycled using an aqueous-organic mixture and the quality of recycled fibers will be tested. This project demonstrates efficient and sustainable technology that provides insight into (a) optimizing in-process manufacturing of wind turbine blades, and (b) effective recycling for both production waste and end-of-life wind turbine blades.