Study On Preparation And Flame Retardant Properties Of Loof Ah Flame Retardant Composites

Loofah（LF）is a fibrous network structure material obtained from loofah after treatment.It has the characteristics of high strength,high permeability,non-toxic,low price,degradable regeneration,wide source and natural three-dimensional filamentous network structure.It is widely used in many fields,such as packaging,sound and heat insulation,building and home decoration,adsorption materials and so on.However,the limiting oxygen index（LOI）of untreated LF is only 16%,and there is thick smoke during combustion,which has great fire risk.Therefore,the research on flame retardant modification of LF fiber is of great significance to improve the application safety of LF fiber and its functional materials and promote its high-value development and utilization.In this paper,LF was used as the base material.Melamine,phosphoric acid and silica aerogel（SA）were used as flame retardants.LF was treated by impregnation,baking,sol-gel and microwave grafting respectively.The physicochemical properties and properties of the materials were studied.The main contents and results were as follows:（1）LF fiber flame retardant composite（LFR）was prepared by impregnation baking method and flame retardant modification of LF with melamine.Orthogonal design and range analysis were used.By investigating the mass concentration of melamine（ρ_m,g/L）,loofah complex bath ratio（LBR）,reaction temperature（T_r,°C）and reaction time（t_r,h）.The preparation conditions were optimized with adsorption rate（AR）and LOI as reference values.The optimum conditions are as follows:ρ_m is6.0 g/L,LBR is 1:100,T_r is 80.0°C,t_r is 2.0 h.The results of thermogravimetric（TG）,micro calorimeter（MCC）,scanning electron microscope（SEM）and smoke density test show that the flame retardant properties of the flame retardant composites prepared under the optimum conditions have been effectively improved.Loi was 27.5%.The vertical combustion level rises to V0 level.The peak heat release rate（PHRR）and total heat release（THR）decreased by 36.3%and 56.7%respectively compared with LF.The smoke suppression ability of the material has also been improved.（2）Using cheap water glass to produce SA in the cavity of LF fiber by sol-gel method,the flame retardant composite LF@SA with different SA ratios was prepared by changing the dilution ratio of sodium silicate.The heat release properties,microstructure of residual carbon,thermal stability and flame retardant and smoke suppression properties of LF@SA were studied.The results show that the introduction of SA can not only effectively improve the flame retardant and smoke suppression performance of LF,but also benefit from many cavities in LF fiber and excellent water absorption,which greatly enhances the loss resistance of flame retardant in the material.Prepared when the dilution ratio of water glass is 1:4 LF@SA2,its flame retardant and smoke suppression level is the best,compared with other samples,LF@SA2 With the lowest THR(6.8k J·g^-1)and PHRR(136.2 W·g^-1).LOI increased to 31.2%,and the smoke transmittance increased from 5.51%of LF to 98.07%,showing excellent flame retardant and smoke suppression ability.（3）Flame retardant composite LF-P-M was prepared by microwave grafting with melamine and phosphoric acid.The group composition of LF-P-M was characterized by infrared spectroscopy（FT-IR）and X-ray photoelectron spectroscopy（XPS）,which proved that the material was successfully prepared.Taking the grafting rate as a reference,the optimal microwave irradiation time was determined as 1 min for a single time and20 min for a total time.The test results of LOI,MCC,TG,SEM and smoke density show that the flame retardant performance of LF-P-M3 prepared under the best reaction conditions has been effectively improved.Compared with LF,PHRR and THR of LF-P-M decreased by 29.0%and54.5%respectively,and the generation time of flue gas was delayed by 470s.In addition,the material LF-P-M modified by flame retardant grafting has strong loss resistance and can still maintain its flame retardant performance after repeated washing.