According to this research, the polyurethane-based composites outperformed epoxy and vinyl ester samples in is terms of fatigue and fracture toughness properties. They also exhibit faster demould than resins currently used in wind turbine blade manufacture.
In addition, the polyurethane systems contain low, or no, volatile organic compounds (VOCs) and use sustainable raw materials from renewable resources.
The results of the study were detailed in a presentation at the SAMPE Tech 2011 conference and exhibition on 17-20 October in Fort Worth, Texas, USA. The paper, Polyurethane Composites for Wind Turbine Blades, was authored by Dr Usama Younes, principal scientist with Bayer MaterialScience LLC, and Frank Bradish, a researcher with Molded Fiber Glass Research Company.
Bayer notes that while glass reinforced polyurethane composites have been used for many years to make parts used in agricultural equipment, heavy-duty construction equipment and watercraft, they were designed for fast throughput and are known for fast gelling and fast demould properties. This made them unsuitable for the manufacture of very large wind turbine blades, which require polyurethane systems with lower viscosities and longer gel times.
However, the studies performed by Younes and Bradish demonstrate that new polyurethane products have been developed and adapted to current large blade manufacturing processes and retrofitted into existing designs at minimal cost.