Synthesis Of Novel Intumescent Flame Retardants Based On ?-cyclodextrin And Their Application In PLA

Polylactic acid(PLA)has attracted more and more attentions from academia and industry because of its renewable and degradable properties.Its application has extended from the initial packaging materials to the electronic,automobile and other fields.The flammability of PLA limits its application,as well as causes the fire risk indirectly or directly.Therefore,the study of combustion and flame retardancy of PLA is urgent and necessary.It is important to fonn a protective carbonaceous layer on the surface of the matrix during the combustion process for the intumescent flame retardant system(IFR).IFR mainly consists of a carbon source,an acid source and a blowing agent.Not only does cyclodextrin have the simple and thermal stable structure,but also it has many hydroxyl groups which dehydrate during combustion,thus help to form the protective carbonaceous layer.So,cyclodextrin is a promising carbon source to be explored and studied.Moreover,cyclodextrin is produced from renewable resources instead of fossil fuels,which may provide us a new method of flame retardant green plastic using biomass materials.In this paper,a novel intumescent flame retardant that integrates all the three sources was synthesized by using(3-cyclodextrin(CD)and phosphorus-nitrogen flame retardant(PAB).The flame-retardant PLA composites(PLA/CD-nPAB)were prepared by melt blending.The effects of CD content in the IFR on the thermal stability and flame retardancy of PLA composites were studied.The results show that the addition of CD-nPAB improves the thermal stability and flame retardancy of PLA.In addition,the suppress effect of smoke was enhanced with the increase of the mole percent of CD.Combining the results of TG-IR and CONE,we know that CD helps the matrix to form a porous carbon layer during combustion.What's more,CDs may have the ability of capture some small molecules of aliphatic hydrocarbons.Then,?-cyclodextrin was modified by phenylphosphonic acid dichloride(BPOD)to obtain PCD,which was blended with ammonium polyphosphate(APP)to prepare flame retardant PLA composite(PLA/APP-PCD).The results show that the system has excellent thermal stability and flame retardancy.Its LOI value increased from 19.7%of pure PLA to 35.1%with only 20wt%APP-PCD(5:1)added and the system obtained VO classification of UL-94 test.The synergistic effect of APP and PCD in flame retardant PLA and the ability of CDs to capture small molecules was studied by TG-IR.The effect of phosphorus modification to CD on the system was studied by comparing the CD/APP system and PCD/APP system using cone calorimetry.