Preparation Of DOPO Derivatives Flame Retardant And Study On Flame Retardant Properties Of Poly(Lactic Acid) Composites

Poly(lactic acid)(PLA)is an environmentally friendly biodegradable material.Because of its good biocompatibility and biodegradability,it has become one of the most promising candidates to replace traditional petroleum-based materials.However,PLA has been greatly restricted in many application fields due to its flammability and poor crystallization ability.Therefore,it is of great significance to improve the flame retardant and crystalline properties of PLA.In this paper,4,4'-diaminobenzophenone(DABP)and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)were used as starting materials to synthesize and characterize a DOPO derivative(CP)that containing phosphorus and nitrogen.Secondly,CP and ammonium polyphosphate(APP)were blended and their effects on the combustion behavior,thermal stability,flame retardancy and crystallization properties of PLA were analyzed.The results of the study are as follows:The flame retardant CP was successfully synthesized by Fourier transform infrared spectroscopy(FTIR),wide-angle X-ray diffraction(WAXD)and X-ray photoelectron spectroscopy(XPS),and the microscopic morphology was flocculent by scanning electron microscopy(SEM).The thermal stability,flame retardancy and combustion behavior of PLA flame retardant composites were tested by vertical burning test(UL-94),limiting oxygen index(LOI),thermogravimetric analysis(TGA)and cone calorimetry test(CONE).The results showed that the LOI value of PLA/5%CP/10%APP reached 35.2%,and it had good thermal stability.At the same time,the UL-94 of the composite materials with CP and APP reached the V-0 level.The combustion parameters of PLA/5%CP/10%APP were the lowest,and the flame retardant effect was the best.The carbon residue after cone calorimetry was characterized by energy dispersive spectroscopy(EDS),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR)and Raman spectroscopy(LRS),The results show that with the increase of flame retardant,the elements of P and N in the carbon layer gradually increase,and the carbon layer gradually becomes dense from loose;FTIR showed that PLA/5%CP/10%APP formed a phosphorus-rich carbon layer after combustion;LRS showed that PLA/5%CP/10%APP had the highest degree of graphitization and the best thermal stability.The gaseous products of PLA and its composites were characterized by thermogravimetric-infrared(TG-IR)and pyrolysis gas chromatography/mass spectrometry(PY-GC/MS).The results showed that incombustible gas was generated during the combustion,and free radicals such as PO· and HO· and other free radicals produced by PLA further inhibited the degradation of PLA.Differential scanning calorimetry(DSC)showed that PLA/5%CP/10%APP had the best crystallization properties.