| Fire disaster is one of the largest world-wide impact of natural disasters, which has caused tremendous life and property losses to human society. Many fires disaster occur and expansion are closely related to the wood lack of fire-resistant, so, wood flame-retardant treatment is important for the protection of life and property security of the people. But after flame retardant treatment for wood, due to the flame retardants suppressed full combustion of wood, flue gas emissions of incomplete oxidation of toxic components dominated by CO fold increase, this caused serious "secondary pollution". Therefore, when the wood treated with flame retardants, it is necessary to suppress smoke and reduce toxic at the same time, the mainly purpose is to reduce the emission of smoke and toxic gases represented by CO. Both molecular sieves and aerogel materials have large specific surface area, so they have certain adsorption, catalysis and load capacity; transition metal elements have strong catalytic oxidation ability to CO, NOx and other incomplete oxidation components, which can be commonly used in the automobile exhaust gas purification. In view of these advantages of porous materials and transition metal elements, this paper is about taking the porous material as a carrier, loading transition metal elements which can catalytic oxidation CO on the porous material, then mixing with ammonium polyphosphate(APP) to flame retardant for particleboard. Explored smoke suppression and toxic reducing effect of these two kinds of porous materials in the particle board flame retardant. What is more,in situ APP/aerogels composite flame retardant system of the process and the smoke suppression and toxic reducing effect has also been investgated.(1)APP have efficient flame retardant effect for wood particleboard, but represented by CO poison gas release sharply increased. The test results show that:total heat realease of pure APP flame retardant wood relatively blank reduced 46.9%, total smoke production reduced 55.7%, but the average yield of CO(COY) is 2.09 times relatively the blank, causing serious "secondary pollution".(2)Metal-modified zeolites-APP composite handle wood particle board not only have good flame retardant effect, but also the smoke and toxic gas emissions are greatly reduced. The test results show that:THR of iron, copper modified zeolites-APP decreased 36.8%,39.8%, TSP reduced 69.3%,72.8%, COY reduced 40.2%,44.5%. Synergy effect of molecular sieve and APP can reduce the formation of amorphous carbon, so that the carbon layer structure is stable, prevent the carbon layer burst effectively, and delaying combustion of inner layer wood, the second exothermic peak reduce significantly and the peak time delayed, which can reduce the risk of wood in the fire.(3)The flame retardant, smoke suppression and toxic reducing effect of aerogels are better than zeolites, metal-modified aerogels has excellent smoke suppression and toxic reducing effect, metallic element increased the catalytic activity of the aerogels, and the catalytic efficiency is improved. The study results show that:the average heat release rate (a-HRR) of aerogels-APP processed particle board 11.1% lower than the molecular sieve, THR 7.2% lower than the molecular sieve; iron, copper modified aerogels-APP THR relatively blank decreased 40.3%,42.1%, TSP were reduced by 73.1%,75.9%, COY were reduced by 49.3%,53.3%. Low density and high porosity properties of aerogels have positive impact on the flame retardant, smoke suppression and toxic reducing, the aerogels composites with APP ensure flame retardant efficient while achieving less smoke and low toxicity. Aerogel excellent insulation properties lead to the characteristics decomposition temperature hysteresis and weight loss rate decreased, the residual carbon surface microstructure density degree analysis showed that, carbon layer of aerogel formed denser than the zeolites, carbon layer structure is more stable, it can be effectively isolated inner layer wood from heat and mass transfer, played a very good protection for the inner layer of wood.(4)Vacuum-pressure impregnated wood treatment process conditions:under room temperature, using HCl-HF composite catalyst catalyze ammonium polyphosphate/ethyl orthosilicate(APP/TEOS)solution, n(HCl):n(HF)=1.2:1,the composite catalyst dosage is 3%, under 0.5 MPa pressure packing 7 hours, the drug loading rate can reach 20%. Studies have shown that:After catalysis, impregnation and freeze drying steps, the APP/aerogel composites has in situ generated inside the wood. Situ the APP/iron, copper modified aerogels retardant wood samples does not burn in the radiation intensity by 50 kW/m2, and compared to the blank THR decreased 86.8%,90.5%, TSP were reduced by 68.8%,71.6%, COY were reduced by 72.4%,73.1%, the wood in situ generated APP/aerogel flame retardant system has excellent flame retardant,smoke suppression and toxic reducing effect. APP present in the aerogel porous structure as a guest substance, released from it when fire disaster occur and play the role of flame retardant, the metal-modified aerogel as an adsorbent and catalyst, it can directional catalytic conversion the incomplete oxidation of toxicity component represented by CO to low-toxic or non-toxic products, to achieve the purpose of smoke suppression and toxic reducing.The main innovation of this paper is that both porous material molecular sieve and aerogel has been applied to the study of wood smoke suppression and toxic reducing in wood flame retardant, modified two porous materials with transition metal elements which have catalytic oxidation ability, the perfect combination of metal-modified aerogel and APP can achieve efficient flame retardant to wood, which also have little smoke and low toxicity at the same time, according to the study has been introduced, one set of in situ generated APP/aerogel technology and methods has been developed, and a basis for scientific and experiments has been provided for wood flame retardant techniques and theories. |
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