Study On The Modification Of Chinese Fir By Silica Sol To Enhance Wood's Fire-resisting Property

As a natural resource, wood is environmentally friendly, renewable, beautiful, and with excellent mechanical properties .And now it has regained people's attention in construction industry. In our country, natural wood resources are increasingly protected, so fast-growing plantations, as the replacements, have been playing an increasingly important role in the industries of wood-based panels, doors and windows, furniture, etc. For the wood is an easily ignited material, fire-retarding treatments of the fast-growing plantations is of great significance.At present, wood retardants can be classified into three main categories as organic retardant, inorganic retardant and resin-based flame retardants. Organic retardants can provide good fire-resisting properties, while they are expensive, and release toxic gases while burning. Inorganic retardants are non-toxic, while with poor performances on anti-loss and relatively low fire-resisting efficiency. As to the resin-based retardants, they work together with inorganic retardant, and can highly enhance the anti-loss performance, this kind of retardants have just been put into industrial production. Studies will be focused on developing retardants with the properties of low toxicity and smoke suppression, high fire-resisting, using nano-technology. Scholars at home and abroad tried to modify wood's property with sol. Studies on Purple linden and alder by Qiujian found that, compared to the material, wood / SiO2 aerogels composite materials have a much better fire-resisting property. In general, there are few reports about treating wood with sol as a retardant.In the experiments of the study, finished sol is used for impregnating fir, the most important fast-growing artificial fir tree in south China. And we get Wood / SiO2 xerogel composite materials after drying. Influence on impregnation effects of the these factors, such as soaking time, pressure, material difference and initial moisture content of samples, are studied. Wood samples are taken combustion tests to analyze the modification of fire retardant by the treatment of silica sol; A more comprehensive evaluation of wood treatment with silica sol is made by taking more tests on mechanical properties, anti-corrosion, dimensional stability, moisture absorption and anti-extraction value of the samples.Study results show that:1)according to 0.5～4h drug-loading rates, drug-loading rate and the depth of drug-loading increase over time, and 0.5h is relatively a suitable soaking time; material differences of samples from the same species of wood can significantly affect the treatment results; soaking experiments with pressure under 0.5MPa show that, soaking pressure has an obvious effect on the impregnation, drug-loading rate increase significantly with pressure; the initial moisture content of the samples, if it is under the air-dry moisture content (14% -17%),will have little effect on the final the drug-loading rate.2) SEM results show that, basic structure of wood does not change after the modification, inside wood cell walls and cell cavities and conduits are filled by sol.3) Tests by Cone Calorimeter shows that the modification of silica sol apparently improves the fire-retardant performance of the wood. In terms of mechanical properties, corrosion protection, moisture absorption and dimensional stability, it has only a slight role of enhancement; Samples modified by silica sol owns a perfect Anti-loss performance.