Synthesis Of Biobased Flame Retardant And Study On Its Flame Retardant PLLA

Polylactic acid（PLLA）is a biopolymer of starch-fermented lactic acid polymerization.It has excellent degradability and is widely used in various fields,so improving its flammability has become an urgent need.Chito-oligosaccharide（COS）is a kind of alkaline amino oligosaccharide,and it is the only oligosaccharide containing amino with a positive charge in nature.In this paper,based on the biomass raw material,flame retardant was prepared,mixed,and filled in PLLA,and its effect on the flame retardant property of PLLA was studied1.In this part,the green flame retardant COPD was synthesized by a two-step reaction using COS,4-hydroxybenzaldehyde（PHBA）,and 9,10-dihydro-9-oxygen-10-phospho-10-oxide（DOPO）as raw materials.Infrared,ultraviolet,and ¹H nuclear magnetic resonance spectra（¹HNMR）proved the synthetic products.COPD was blended with PLLA solution to prepare the thin film material.The effect of the blending ratio on flame retardancy and the mechanical properties of the materials was studied.When the COPD/PLLA blend ratio is20/80,the limiting oxygen index（LOI）can be increased to 25%,and the UL-94 grade of flame retardant COPD can be V-1.The heat release rate（HRR）,total heat release rate（THR）,and effective heat release rate（EHR）of cone calorimetry were all reduced.During combustion,the good carbon reinforcing the ability of the material can cooperate with the gas phase process to realize the flame retardant effect.Due to poor compatibility,the dispersion of COPD in the PLLA matrix is limited,thus affecting the mechanical properties of the material.2.In this part,the structure of the flame retardant was adjusted,and the multipoint flame retardant COMD containing N,S,and P elements was synthesized from COS,4-methyl sulfonyl benzaldehyde and DOPO,which was used for flame retardant PLLA toughened with low molecular weight PEG.The product was characterized by ¹HNMR and thermogravimetric analysis（TGA）.COMD was blended with PEG/PLLA solution to prepare thin films.PEG does not affect flame retardant.When COMD content is 20wt%,LOI is 25.5%,UL-94 reaches V-0,HRR,and THR are reduced.During combustion,many elements produce corresponding non-combustible gases such as NH₃,CO₂,and phosphor oxygen free radicals to dilute the concentration of combustible gases.In COS,a large number of elements such as C,P,and S form corresponding sulfonic acid and phosphorus compounds to form a carbon layer to isolate heat.Under the joint action of the gas phase and condensation phase,a good flame retardant effect is achieved.This provides a new way to promote the application of PLLA.