Composite Materials From Chemically Modified Wood
Small pieces of wood can be mixed with a glue, heated to the temperature that can be used to bake pizza’s and pressed together in a special machine to make a very large piece of composite wood that is used to build houses. We are trying to make better composite wood by taking out part of the wood before it is baked. Hot water and pressures are used to remove chemical compounds called hemicellulose. The goal is to determine what is the right amount to remove and to measure how the composite wood is improved.
This study evaluated the influence of hot water extraction on hemicellulose removal, the change in wood properties, and finally production of OSB from the modified wood. Three red maple (Acer rubrum L.) trees were felled, debarked, and their butt logs used to produce strand dimensions were of 4 in. length and a target thickness of either 0.025”, 0.035”, and 0.045”. Two hot water extraction procedures (160 C, 90 psig) of 45 and 90 minutes duration (plus 50 minutes of preheating) treatments were used, resulting in an average weight loss of 16.4 and 17.2%, respectively. Weight loss was significantly influenced by extraction time (p=0.0011) and tree source (p=0.0001) while the influence of strand thickness was not statistically significant (p=0.1026). One OSB panel (17.6” x 12.4” x 0.5”) was manufactured for each of the 27 material combinations (2 extraction conditions, control, 3 trees, and 3 strand thickness). Panels were blended individually with a resin load of 3.2% pMDI resin, no wax, and an average density was of 41.8 pcf (test volume basis). Physical and mechanical properties were determined following ASTM D1037-99 procedures. Water absorption for both hemicellulose extraction treatments were significantly higher than the control after 2 and 24 hours and the thickness swell of the extracted panels was slightly improved after 24 hours. The modulus of rupture (MOR) was not significantly altered between the control (5,966 psi) and the 45 minutes of extraction time (6,162 psi) panels while the 90 minutes extraction time (4093 psi) was significantly lower. Internal bond strength in dry conditions from both extraction times were significantly lower than the control (117 and 37 psi), and similar results were obtained in wet condition (35 and 15 psi).
What’s New on this Project?
Panels made of Southern Yellow Pine have been made and the volatile organic compound (VOC’s) emitted during that process has been collected using a closed caul plate. The specific chemical compounds present will be analyzed using Liquid Chromatography Mass Spectroscopy (LCMS) and the absolute amounts emitted quantified.