Environmental Degradation of Fiber-Reinforced Polymer Fasteners in Wood

Abstract

This paper examines the durability of fiber-reinforced polymer (FRP) nails in treated wood. The FRP nails were exposed to four conditions: (1) accelerated weathering, consisting of exposure to ultraviolet light and condensation; (2) 100% relative humidity (RH); (3) being driven into untreated wood and exposed to 100% RH; and (4) being driven into wood treated with alkaline copper quaternary (ACQ) and exposed to 100% RH. Changes in the physical, mechanical, and chemical properties were examined with weight loss, dynamical mechanical analysis (DMA), and near-infrared spectroscopy (NIR), respectively. Although fasteners exhibited changes after exposure to treated wood, the changes were not statistically different than the changes that occurred in untreated wood or in the humid environment. Under these three conditions, the fasteners gained 2–3% of their starting mass, and the storage modulus also increased by 20% after exposure. The results suggest that moisture is more important than the wood chemistry or preservative chemistry in determining the durability of FRP fasteners in wood.