Effects of UV curable urethane acrylate resins treatments on the physical properties of medium-and small-diameter softwoods

摘要

This study analyzed the effects of ultraviolet curable urethane acrylate resin (UV resin) treatments on surface homogeneity, dimensional stability, and change in colors of medium-and small-diameter softwoods produced in Taiwan. The UV resins were formulated with urethane acrylate oligomer/methyl methacrylate (MMA) monomer by the weight ratio of 50/50, 60/40, 70/30, 80/20, and 90/10, and 3% of photoinitiator (benzil dimethyl ketal) by the total weight of UV resins was added, respectively. Four kinds of softwoods, including Taiwanina, China fir, Taiwan incense cedar and Japanese fir with a diameter of 10-15 cm were obtained from Hui-Sun Forest Station, Taiwan. Results show that the oligomer derived from 2-hydroxyethyl methacrylate (2-HEMA) and polymeric toluene diisocyanate (PTDI) by the molar ratio of NCO/OH = 1.0 could be readily synthesized and the prepared UV resin were also easily applied to the woods at room temperature and normal pressure. The surface hardness and moisture excluding efficiency (MEE) of woods were markedly enhanced and correlated with the increased in oligomer content of the UV resins as well as the homogeneity of softwood surfaces were also improved. According to the antiswelling efficiency (ASE), the increased in dimensional stability of woods were achieved; especially for the lower specific gravity China fir had the greatest improved efficiency of 60.68% at oligomer/MMA ratio of 80/20. In addition, a massive, colorful, and warm feeling in sense of sight on UV resintreated wood, which would appeal to most people, was also obtained.