Study On Flame-retardant Functional Lignocellulosic Fiber Prepared By Mechanochemical Method And Fire Safety Properties Of Its Fpuf Composites

Lignocellulosic fiber(LF)is the largest reserve of biodegradable and renewable biomass on earth,with many aromatic structures and rich hydroxyl groups,showing excellent high carbonization performance,and has become one of the most potential next-generation of environmental flame retardants.However,realizing the fire safety design of flexible polyurethane foam(FPUF)with lignocellulosic fiber-based flame retardant(LF-FR)has become a complex problem in flame-retardant polymers.Recently,the development of the mechanochemical method has made it possible to realize the nano and flame-retardant functionalization of LF,and provided technical support for the design of LF-FR for flame-retardant surface treatment.This work synthesized a new kind of flame-retardant functionalization LF-FR(LFPN)by the aqueous ball milling method.And the FPUF@LFPN composite was prepared by LFPN flame-retardant coating.At the same time,a series of composites based on FPUF@LFPN were prepared using multi-element synergism and surface design,which further improved the comprehensive fire safety performance of the FPUF@LFPN composite.In addition,the mechanism of LFPN-based composite flameretardant coating was revealed by exploring the relationship between composition,structure,and property.The main research contents and conclusions are as follows:1.Phosphorous-nitrogen functionalized lignocellulosic fiber-based flame retardant(LFPN)was prepared by aqueous ball milling using LFPN and ammonium polyphosphate as raw materials.LFPN presents a short rod-like nanofiber structure covered by nanoparticles,and its surface is rich in phosphorus and nitrogen elements.Meanwhile,LFPN has good carbonization and water dispersion stability,suitable for flame-retardant surface treatment of porous polymers.2.LFPN flame-retardant coating was used to finish the surface of FPUF by the polyelectrolyte-assisted deposition method.It is found that the loading capacity of LFPN can be increased to 21.7% within 20 minutes,and the compression resistance of FPUF can be significantly improved.FPUF@LFPN composite has a 269.3% increase in char residue at 700 ℃,a 110.6% increase in its fire performance index(FPI),and can pass the vertical flammability test.In addition,the mechanism of gas-condensed dual phase and chemical-physical coupling flame-retardant action for FPUF@LFPN.3.The FPUF@LFPN@ZIF-67 composite was constructed by in-situ polymerization and deposition of ZIF-67 nanoparticles on the surface of FPUF@LFPN.ZIF-67 nanoparticles can significantly improve the smoke suppression,toxicity reduction,and compression resistance of the FPUF@LPFN composite.The peak smoke release rate(p SPR),average specific extinction area(Avg-SEA),and average carbon monoxide yield(Avg-COY)of the FPUF@LFPN@ZIF-67 composite were reduced by42.2%.57.4% and 51.5% compared with the FPUF@LFPN composite.In addition,coupling analysis of pyrolysis products and combustion products revealed the mechanism of smoke suppression and toxicity reduction based on “inhibition” and“catalysis”.4.The biomimetic multifunctional coating composed of layer dihydroxides derived from metal-organic frame materials and low surface energy silanes(MOFLDH@HDTMS)was constructed using the sacrificial template and covalent grafting method.The composite coating not only reduces the fire risk of FPUF and improves the compression resistance of FPUF but also has excellent coating durability.FPUF@MOFLDH@HDTMS composite has significantly lower p HRR,p SPR,and Avg-COY than FPUF,and its water contact angle is up to 153.3°,maintaining its original performance even after destructive testing,showing the excellent comprehensive fire safety performance.