Preparation and properties of halogen-free and phosphorus-free environment-friendly flame-retardant system for polyamide microfiber synthetic leather
Objective As an excellent substitute for natural leather,microfiber synthetic leather(MSL)is widely used in aerospace,high-speed rail,domestic decoration and other fields because of its excellent performance such as air permeability and wear resistance.However,MSL is composed of flammable polymers like polyamide,polyester,and polyurethane.When it burns,serious droplet melting occurs,endangering personal safety.As a result,it is critical to endow MSL with flame-retardant properties.Method In order to solve the flammability of polyamide microfiber synthetic leather(PA/MSL),layer by layer self-assembly technique was applied using biological polysaccharide carrageenan(KC)as anion component,and polyethylenimine(PEI),(3-aminopropyl)triethoxysilane polymer(APTES)and their mixtures as cationic components.The influence of different components on the flame retardation of PA/MSL was investigated.Results Compared with the control sample,the modified MSL presented some additional characteristic peaks responding to KC,PEI and APTES in the infrared spectra.In addition,the surface of the modified MSL was covered by the flame-retardant coating.Meanwhile,S and Si elements with uniform distribution were detected in the modified MSL,which were from the KC and APTES,respectively.The results indicated that the flame-retardant coating was successfully assembled on the surface of MSL.The flame-retardant performance of the modified MSL were analyzed by vertical flammability test(VFT)and limited oxygen index(LOI).KC/PEI and KC/APTES were found to improve the flame retardant performance of MSL with LOI values of 24%and 26%.Furthermore,the modified MSL by ternary self-assembly systems(KC/APTES/PEI)presented perfect flame retardancy with LOI value of 37%,and self-extinguishing behavior could be achieved without melt-dropping in VFT.The thermal stability of the modified MSL was analyzed through thermal degradation.Compared with control sample,the carbon residue of the modified MSL was increased to 14.2%at 800℃in nitrogen gas atmosphere.The carbon residue of modified MSL by KC/APTES and KC/APTES/PEI showed characteristic peaks belonging to Si-O-Si bonds,indicating the formation of silicon-carbon chemical compounds.Meanwhile,silicon or sulfur elements were maintained in the char residues.The combustion behavior of control sample and modified MSL were studied by cone calorimetry test.The total heat release and total smoke release of modified MSL did not decrease as compared to the control sample.Still,the increased TTI demonstrated that the assembled coating had some effect on increasing the flame-retardant performance of the MSL.Conclusion The influences of different cationic and anionic components on the flame retardant and anti-dripping properties of PA/MSL were investigated using layer by layer self-assembly technology.The flame-retardant performance and thermal stability properties of modified MSL were analyzed.The results showed that all flame-retardant coatings significantly improve its carbon formation capacity.Meanwhile,the ternary self-assembly systems(KC/APTES/PEI)greatly improved the flame-retardant performance of PA/MSL and the LOI values increased to 37%with self-extinguishing behavior and anti-drip phenomenon.This study presented a facile method to prepare flame-retardant MSL with non-phosphorous flame-retardant coating,which promotes the green development of flame-retardant materials.
microfiber synthetic leatherflame retardantanti-drippingbio-polysaccharide carrageenanlayer by layer self-assemblypolyamide
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