Effect of polyvinyl pyrrolidone on the dimensional stability and leachability of copper from wood treated with ammoniacal copper formulations

Two major problems associated with treated wood are poor weathering charact eristics and leachability of the biocidal components. In this study, the po ssibility of using polyvinyl pyrrolidone (PVPy) to improve the weathering p roperties by imparting water repellency and also to reduce the leachability of copper from ammoniacal systems was explored. The addition of high- and low-molecular-weight PVPy to ammoniacal copper carbonate and ammoniacal cop per berate formulations imparted considerable water repellency to pressure- treated wood. Mixed results were obtained when the treated wood was subject ed to a simulated weathering cycle, but in most cases a high degree of wate r repellency was retained. Wood treated with PVPy alone exhibited reasonabl e water repellency, but higher values were obtained when it was combined wi th the ammoniacal copper systems. The addition of this polymer to boric aci d and didecyldimethylammonium chloride formulations also imparted good wate r repellency to dip-treated wood. The effect of PVPy on the leachability of copper from wood treated with amended formulations of ammoniacal copper ca rbonate was also examined and found to be very effective in reducing the de pletion of this element when the treated wood was exposed to wet soil.