Studies On Flame Retardancy And Combustion Properties Of Typical Decorative Textiles In Tibetan Historical Buildings

Due to the culture of Tibetan Buddhism,Tibetan historical buildings display mysterious and particular historical values.The large amounts of hanging decorative textiles with various clear patterns and lustrous colors are the direct carriers of such religious values.However,the flammability of these fabrics poses great potential safety hazards on such particular values.In this paper,based on the requirement for both flame retardancy and religiousness of typical hanging decorative textiles in Tibet historical buildings,high efficient,environment-friendly,transparent,convenient and novel flame retardant methods are explored.Firstly,the pyrolysis and burning properties of typical textiles were measured;secondly,the compositions of typical textiles were identified to confirm the base fabrics;thirdly,a series of transparent inorganic oxide sols were prepared via sol-gel technique and used to finish cotton and PET fabrics by dipping-drying,the flame retardant effects and mechanisms of such finished fabrics were studied;fourthly,various base forming metal salt solutions were prepared to finish cotton and PET fabrics by dipping-drying,the flame retardant effects and mechanisms of such finished fabrics were studied;finally,sols,metal salts and traditional flame retardants of high efficiency were selected to compound finish cotton and PET fabrics successively,the synergistic effects between them was investigated.The main work in this paper is summed up as follows:(1) Limiting oxygen index,vertical burning,cone calorimeter,simple burning using small ignition source and thermal gravimetric analysis methods were used to measure the pyrolysis and combustion properties of typical hanging textiles sampled from the Potala Palace.The results show that most of them are flammable fabric with LOI values lower than 20.0;they degrade at lower temperature and lead to less char residues;in the cone calorimeter test,they show high burning rates(ignition time values are usually lower than 60s) and high heat release rates(higher than 50kW/m²). Therefore,the demand for flame retardancy is very high.(2) The fiber compositions of typical hanging textiles were identified via thermal gravimetric analysis,simple burning,optical microscope projecting and Fourier Transition Infrared Spectrum(FTIR) methods.It is found that cellulose fibers (viscose and cotton),manmade polymer fibers(PET＜terylene＞,PA＜nylon＞and PP) and protein fibers(silk and wool) are applied most widely.Hence,cotton and PET fibers are selected as flame retardant bases.(3) A series of inorganic oxide sols like SiO₂,TiO₂,SnO₂ and Fe₂O₃ were prepared via sol-gel technique.They were used to finish cotton and PET fabrics via dipping-spraying.Flame retardant effect was determined via limiting oxygen index method and the pyrolysis and combustion properties of finished fabrics were measured by thermal gravimetric analysis and micro-calorimeter methods.Flame retardant mechanism was explored via dynamic FTIR and scanning electronic microscope(SEM).The results show that inorganic oxide sols play limited role in flame retarding cotton and PET fabrics.Theâ–³LOI values of finished cotton and PET fabrics lie only in 0.0-3.0 and 0.0-2.2 respectively.Finished fabrics cannot reach the B2 rating(LOI≥26.0) recommended by the department standard GA 504-2004 (Flame-retardant decorative textile).SnO₂ sol shows the best flame retardant capacity on cotton fabrics.Its primary mechanism is to catalyze and maintain the dehydration and char-forming reactions.(4) A series of solutions of base forming metal chlorides,sulfates,nitrates and acetates were prepared and used to finish cotton and PET fabrics via dipping-drying. Flame retardant effect was determined via limiting oxygen index method and the pyrolysis and combustion properties of finished fabrics were measured by thermal gravimetric analysis and micro-calorimeter methods.Flame retardant mechanism was explored via dynamic FTIR and scanning electronic microscope(SEM).The results show that metal salts show high flame retardant effect on cotton fabrics in the descending order of metal chlorides,sulfates,acetates and nitrates.Their finished fabrics show/kLOI values of 1.3-15.3,0.4-14.4,0.0-6.5 and 0.0-3.0.Cotton fabrics finished by FeCl₃·6H₂O,MgCl₂·6H₂O,ZnCl₂ and Al₂(SO₄)₃·18H₂O can reach the B1 rating(LOI≥32.0) recommended by GA 504-2004 standard.The peak heat release rate values can be reduced by 67-90%and the amounts of char residues can be increased by 4.01-8.12%.The high flame retardant efficiency of such metal salts lie in their durative catalyzing dehydration and char-forming reactions.However,there are only limited role in flame retarding PET fabrics since B2 rating cannot be reached.Their flame retardant effect is descended in the order of metal chlorides,sulfates,nitrates and acetates.Theâ–³LOI values finished by such salts are 0.5-5.7,0.0-3.9,0.0-3.5 and 0.0-2.2.(5) Sols,metal salts and traditional flame retardants showing high flame retardant effects were selected to compound finish cotton and PET fabrics via dipping-drying method.Flame retardant effect was determined via limiting oxygen index method and the pyrolysis and combustion properties,of finished fabrics were measured by thermal gravimetric analysis and micro-calorimeter methods.The synergistic effect can be determined if theâ–³LOI_{复合整理} is higher than all ofâ–³LOI traditional flame retardants,â–³LOI sols andâ–³LOI metal salts.It was found that cotton fabrics finished by the complex systems of(Boric Acid/Borax) and MgCl₂·6H₂O,ZnCl₂ and SnO₂ sol,MgCl₂·6H₂O and SnO₂ sol,and CuSO₄·5H₂O and SnO₂ sol can reach B1 rating.The highest values forâ–³LOI,peak heat release rate reduction and char residue amplitude are 20.6-21.5(SnO₂ sol/MgCl₂·6H₂O),95%(CuSO₄·5H₂O/SnO₂ sol) and 9.67%(SnO₂ sol/CuSO₄·5H₂O),respectively.The flame retardant mechanism lies in the additive effects of dehydration and char-forming capacities.However,for PET fabrics,these complex systems show limited flame retardant effects(finished fabrics fail to reach B2 rating),...