Wood Protection with Beading Effect
The spruce boards shown here were coated with a water-based impregnation (top image) or coated with a waterborne stain (bottom image) and were then exposed to UV-B light for 1,000 hours. SILRES® WH was added on the right-hand board in each case. The result is a markedly hydrophobic effect.
Wood Protection Possible without Biocides
Wood-impregnating agents are especially designed to protect wood against attack by rot, fungi and insects. The risk of such damage can be mitigated by reducing the moisture content in the wood. Moreover, water-repellent agents go a long way to preserving the appearance of the wood, even though by their nature they cannot prevent UV radiation from turning it gray. The pronounced beading of water-repellent agents acts as a clear sign of effective protection.
Weatherability is the most important criterion by which the quality of water repellents for wood can be judged. Many impregnating agents, such as waxes, exhibit impressive water repellency prior to weathering. But things look very different after one or two years’ open-air weathering or 1,000 to 2,000 hours’ accelerated weathering in the laboratory. By then, organic waxes have been completely degraded, conventional silicone resins have become “chapped” and linear silicones, i.e. silicone fluids, have become extensively soiled. Not so with SILRES® WH, which bestows long-lasting water repellency – as preliminary laboratory tests show. These consisted of immersing a spruce board for three minutes in an impregnating solution composed of one part SILRES® WH and four parts water. The test sample and an untreated board were then artificially weathered in a QUV tester for 2,000 hours. Both boards turn gray due to degradation of the lignin – not even water-repellent silicones can prevent that. However, unlike the untreated board, which sucks up the water like a sponge, the impregnated test sample is still highly water-repellent – the water rolls off the surface in beads.
The water repellency of low-binder wood stains can be impressively enhanced by admixing SILRES® WH.
Technical Marketing, WACKER SILICONES