The Effect Of Inorganic Acid Modified Nanoparticles On Intumescent Flame Retardant Polylactic Acid

Polylactic acid(PLA)is a kind of biodegradable linear polyester,because of it's excellent mechanical properties(high tensile strength and rigidity),good biocompatibility,and ease of fabrication,it is widely used in medical,construction,3D printing and other fields.However,due to the structure of polylactic acid itself,it is easy to burn,and there is a heavy melt dripping during combustion,seriously limiting its application areas.In this paper,the synergistic flame retardant method was used to modify the flame retardants by modifying the nano-particles with inorganic acid.It was used in PLA to improve the flame retardant efficiency.This paper mainly includes the following three parts:1.A novel sulfamic acid intercalated MgAl-LDH(SA-LDH)was prepared by intercalating NH3SO3-into MgAl-LDH through acid-base reaction.The results of characterizations showed that sulfamic acid successfully intercalated into LDH,and the interlayer space of LDH was enlarged.Then it was introduced into PLA resin in association with intumescent flame retardant(IFR)by melt blending to prepare flame-retardant biodegradable PLA composites.The results showed that the composite sample containing 19.0 wt%IFR and 1.0 wt%SA-LDH achieved the maximal LOI value of 48.7%,passed the UL-94 V-0 rating,and significantly decreased the peak heat release rate from 306.3 kW/m2 of neat PLA to 58.1 kW/m2.2.The MgAl-LDH modified by phosphotungstic acid(PWA-LDH)was prepared by the method of reconstruction using the memory effect of LDH.The analysis showed that the phosphotungstic acid is successfully intercalated into LDH.It was applied to the intumescent flame retardant poly(lactic acid)(PLA)composites.The results showed that the PLA/IFR/PWA-LDH composite exhibited excellent flame retardancy and thermal stability,when the total amount was 20%(18%APP/PER,2%PWA-LDH),PLA composite material reached the maximal LOI of 48.3%and UL-94 V-0 grade.The char residue was increased significantly.The char morphology observation revealed that PWA-LDH was beneficial to form dense and compact char layers.The dense char played an important role in hindering the flammable gases and heat exchange by providing a good flame shield for the underlying polymeric substrate to protect PLA matrix.3.The phosphotungstic acid particles were combined with silicon species by hydrogen bond and immobilized in mesoporous framework of silica by fasculation to obtain the product PWA-SiO2.The results exhibited that PWA-SiO2 has a good effect on flame retardant and smoke suppression.the peak heat release rate of PLA/IFR/PWA-SiO2 composite decreased from 306.3 kW/m2 to 42.7 kW/m2,and the total heat release decreased from 41.0 MJ/m2 to 6.9 MJ/m2,and there was little smoke release in the initial stage of material combustion,so PWA-SiO2 was a favorable smoke suppressant.