Study On Combustion Properties Of Thermoset Resins And Silica Sols Modified Wood

Wood modification can raise value and prolong the service life of the wood. As a result, the pressure for the lack of wood can be reduced. The study of modified wood usually focuses on the effects on physical properties and mechanical strength, dimensional stability, and resistance to decay and weathering erosion, but little on the combustion behavior. In this work, Scots pine sapwood (Pinus sylvestris L.) and beech wood (Fagus sylvatica L.) were treated with different concentration of phenol formaldehyde (PF), melamine formaldehyde (MF) resins, AlCl3-modified and non-modified silica sols (Levasil 200E and Levasil 200S) by vacuum-pressure impregnation. The dimensional stability and combustion performance of the modified wood were analyzed and evaluated.Two kinds of thermoset resins (PF and MF) exhibit a proper impregnation for pine and beech wood. Weight percent gain (WPG) of the PF treated wood is approx.54%(pine) and 38%(beech). The WPG of MF treated wood is approx.47%(pine) and 31%(beech). The WPGs of treated wood with two kinds of silica sols are considerably different from pine and beech. The WPG of pine ranges from 10 to 40%, while 5 to 20%for beech wood. Compared with untreated wood, the water absorption rate of PF treated wood decreases by 86.5%(pine) and 54.8%(beech), and the maximum water absorption swelling ratio falls by 8.7%(pine) and 12.3%(beech). Anti-swelling efficiency (ASE) of PF treated wood is 54.1%(pine) and 45.7% (beech) respectively. The water absorption rate of MF treated wood declines 71.2%(pine) and 48.9%(beech), and the ASE of MF treated wood is 20.4%(pine) and 15.6%(beech). According to the experimental result, modification with PF and MF are efficient strategies to improve the dimensional stability of wood. The ASE of Levasil 200E treated wood is less than 0 and the ASE of Levasil 200S treated wood is 13.2%(pine) and 5.8%(beech). Besides the moisture absorption rate of Levasil 200S treated wood decrease approx.1.7%to 3.5% compared source material. Only silica sol Levasil 200S treatment can enhance the dimensional stability of wood.Thermogravimetry shows that treatments with PF and MF reduce the pyrolytic rate, thereby thermally stabilizing the wood. The bench-scale cone calorimetry indicates that the treated wood requires longer time to ignite and yields more char than the untreated control. Treatments with PF do not substantially change the heat release of wood but lead to considerably increase in CO and smoke production. The new compounds in the smoke have been identified to be phenol and its derivatives coming from incorporated PF resin as evidenced by pyrolysis/gas chromatography/mass spectrometry. Treatments with MF cause greater heat release due to complete combustion; however, the smoke production is significantly suppressed. Findings demonstrate that MF treatment can reduce the fire risk of wood; however, high CO concentration and dense smoke production caused by PF-treated wood during combustion may cause potential harm.The bench-scale cone calorimetry indicates that the modification of silica sol Levasil 200E and 200S can improve the fire-retardant performance of the wood. The heat release, smoke production, and CO2 yield were considerably retarded during combustion. In addition, the effect of the woods treated with the silica sol Levasil 200S was more apparent compared to the wood that treated with Levasil 200E. The thermogravimetric results showed that only treatments with Levasil 200S can reduce the rate of wood pyrolysis, and treatments with Levasil 200E did not change the pyrolysis temperature of wood polymers. The pyrolysis products of treated wood with Levasil 200S were affected in a certain extent compared to the wood that was untreated. These findings suggested that aluminium oxychloride in Levasil 200S can lower the fire risk of the treated wood.