Distribution, concentration and bonding factors affecting the performance of water repellents applied to wood
The -effects of water repellent solution concentration, distribution of various components and wood-w9ter repellent bond type were studied using Corsican pine'(Pinus, nigra) and European beech'(Falas*sylvatica) wood. The -resin component protects treated wood by forming an impermeable coating on cell lumina., whilst the wax gives protection by hydrophobic action. Increased concentration and treatment severity cause deeper penetration and increased loading and provide better protection. Water repellents are distributed in highest concentration at the treate; end and in gradually decreasing amounts inwards. Weathering rapidly reduces the effectiveness of the coating action, because in the absence of hydrophobes water is able to gain rapid access to all treated capillaries. However, hydrophobic treatments continue to provide protection to inner wood even after end grain degradation, because water is able to penetrate treated cells only to the depth of the degraded zone. Loss of water repellent effectiveness in the surface zone due to weathering occurs even though hydrophobic substances remain. This is almost certainly associated wi. th degrade of wood structure and wooddeposit bond. Pine specimens were treated with alkylchlorosilanes and alkylene oxides and double treated with an epoxide and a resin-wax water repellent to study the performance of chemically bonded treatments. Both silane and epoxide treatments proved to be resistant to exposure. Silanes provide initial water repellency similar to that provided by resin-wax and are far more resistant to weathering. Loss of effectiveness of silane treatments is attributed to wood degrade enhanced by the effect of HC1 produced in the reaction. Stabilization obtained by epoxides is extremely resistant to exposure. Reduced water absorption, due to OH-group blocking and cell-wall bulking, but no water repellency is shown by epoxy-treated wood. The full potential of water repellents applied to stabilized wood was not realized due to problems encountered in applying resinous solutions to epoxy treated wood.