Preparation Of Poly(Lactic Acid)/HCCP-derivative Composite And Its Flame Retardant Properties

The PLA is a kind of renewable environment-friendly polyester,which has good mechanical properties,biodegradability and biocompatibility,and is expected to reduce environmental pollution caused by traditional petroleum-based polymer materials.Because PLA is easy to burn,which limits its application in some fields.So it is of great significance to modify the PLA,which can wide its application.In this paper,HCCP derivative(PZM)flame retardant with phosphazene(-P=N-)and benzene ring units was synthesized with hexachlorocyclotriphosphazene(HCCP)and 4,4'-diaminodiphenyl ether(ODA).The PZM and ammonium polyphosphate(APP)were added into PLA as the flame retardant(FR).The effects of FR with different proportion and component on the thermal stability,flame retardancy and crystallization properties of the PLA were studied,The mechanism of flame retardant was discussed.The main work is as follows:(1)The molecular structure and thermal stability of the PZM were characterized by FTIR,XRD,XPS and TGA,respectively.The results showed that the synthesis was successful and the PZM had good thermal stability.The carbon residue rate at 700? is 72.4%.(2)The flammability and thermal stability of PLA-FR composites were investigated by LOI,UL-94 and TGA,respectively.The results showed that the addition of the PZM and the APP reduced the initial degradation temperature and the maximum degradation temperature of the PLA,and increased the carbon residue at 600?.When the content of the APP/PZM was 15wt%,the UL-94 of the PLA flame retardant composite reached V-0,and the droplet phenomenon was relieved.The LOI of PLA/10wt%APP/10wt%PZM(PLA-9)increased from 20% of neat PLA to 28.2%.(3)The results of CONE showed that the PHRR,THR,TSR and av EHC of PLA flame retardant composites decreased.Among them,PLA-7 had the best flame retardant effect.It compared with neat PLA,PHRR decreased by 27.2%,THR decreased by 33.6%,TSR decreased by 83.6%,and EHC decreased by 16.9% of PLA-7.The microstructure of carbon layer was observed with SEM,it is found that due to the synergy between APP and PZM,the carbon layer of the PLA flame retardant composites is more compact,continuous and firm,with the functions of heat insulation,oxygen isolation,smoke suppression and drip prevention.(4)TG-FTIR results showed that the flame retardant mechanisms of PLA/APP /PZM system was attributed to solid phase flame retardantance.(5)DSC test results showed that the addition of the PZM improved the crystallization rate of PLA and shorten the crystallization time.