Preparation And Properties Of A Transparent Flame Retardant Poly(unsaturated Phosphate)

Transparent polymer materials have been widely used in biological medicine,electronic packaging,interior decoration,and food packaging because of its outstanding advantages including light weight,easy processing,high transmittance,good thermal stability and so on.However,the flammability of transparent polymer materials has caused great loss to people’s living environment and property safety.This problem can be solved by adding flame retardants to these materials.At present,the halogen flame retardant materials with the largest output are facile to release toxic substances such as hydrogen halide,dioxins when decomposed,which are easy to pollute the environment.The phosphate ester flame retardant materials have attracted much attention,owing to its unique structure of P=O and P-O-C which have great flame retardancy,and nontoxic,low-smoke when decomposed.In this paper,a novel transparent and flame-retardant polymer material was prepared by bulk polymerization with synthesizing unsaturated phosphate monomers containing C=C bond.Then a series of crosslinked copolymers were obtained by modifying the mechanical properties of methyl methacrylate（MMA）and styrene（St）,respectively,and their properties were discussed in detail.The contents of the study are as following:An unsaturated phosphate monomer（UPE）containing C=C was synthesized with triethyl phosphate（TEP）,ethylene glycol（EG）andα-methacrylic acid（MAA）as raw materials.A series of UPE（UPE-1,UPE-2,UPE-3,UPE-4 and UPE-5）were prepared by changing the proportion of MAA.The structure and molecular weight of intermediate trihydroxyethyl phosphate（THPE）and unsaturated phosphate monomer containing three C=C（UPE-3）were studied by Fourier transform infrared spectroscopy（FTIR）and liquid chromatography-mass spectrometry（LC-MS）.The results showed that the stretching vibration absorption peak of C-O-C appeared in UPE-3 at 1299 cm^-1,and the absorption peak of P-O-C spectrum changed obviously.The molecular weight of UPE-3 was 434,which was consistent with the theoretical value.These were confirmed that the esterification reaction was completed successfully.A series of UPE monomers were studied to prepare a series of polyunsaturated phosphate esters（PUPE）（corresponding to PUPE-1,PUPE-2,PUPE-3,PUPE-4 and PUPE-5）by bulk polymerization.The structure and properties of PUPE series were tested via FTIR analysis,gelation degree test,solid ultraviolet absorption spectroscopy analysis,thermogravimetric analysis（TGA）,dynamic mechanical analysis（DMA）,mechanical property test,limiting oxygen index（LOI）test,vertical combustion test（UL-94）,micro cone calorimetric（MCC）analysis and scanning electron microscope（SEM）test.The results displayed that:PUPE with cross-linked structure could be obtained by bulk polymerization of UPE.The initial decomposition temperature(T_0.1)of PUPE exceeded 230℃,the char residue rate of PUPE-3reached 29.07 wt%at 700℃.With the increase of MAA content,the tensile strength of PUPE increased and the impact strength decreased,the transparency of PUPE remained above 90%,the tensile strength,impact strength and transparency of PUPE-3 were 14.62 MPa,30.53KJ·m^-2 and 92.31%,respectively.The LOI value and UL-94 of PUPE were higher than 28%and reached V-0 rating,among the LOI value of PUPE-3 was 32.0%,and its peak heat release rate（PHRR）and heat release capacity（HRC）were 118.2 W/g and 126 J/K·g.A series of crosslinked copolymers（poly（UPE-co-MMA））with different MMA content were prepared by copolymerization of MMA and UPE.The structure and properties of poly（UPE-co-MMA）were tested by FTIR analysis,gelation degree test,solid ultraviolet absorption spectroscopy analysis,TGA,DMA,mechanical property test,LOI test,UL-94 test,MCC analysis and SEM test.The results shown that:The poly（UPE-co-MMA）with cross-linked structure could be obtained by copolymerization of MMA and UPE.With the increase of MMA content,the T_0.1 of poly（UPE-co-MMA）increased,but the char residue rate was reduced to 24.63 wt%from 29.69 wt%of PUPE at 600℃.The tensile strength of poly（UPE-co-MMA）increased to 26.95 MPa from 14.62 MPa of PUPE while the impact strength decreased from 30.53 KJ·m^-2 to 19.26 KJ·m^-2,the transparency remained above 90%.With the increase of MMA content,the LOI value of poly（UPE-co-MMA）decreased to 28.2%from29.0%of PUPE,PHRR slightly increased,while UL-94 combustion grade remained V-0 level.A series of crosslinked copolymers（poly（UPE-co-St））with different St proportion were prepared by introducing St into PUPE.The structure and properties of poly（UPE-co-St）series were tested by FTIR analysis,gelation degree test,solid ultraviolet absorption spectroscopy analysis,TGA,DMA,mechanical property test,LOI test,UL-94 test,MCC analysis and SEM test.The results revealed that:The poly（UPE-co-St）with cross-linked structure could be gained by copolymerization of St and UPE.With the increase of St content,the T_0.1 of poly（UPE-co-St）increased,but the char residue rate decreased from 30.47 wt%of PUPE to21.77 wt%at 600℃.The tensile strength of poly（UPE-co-St）increased from 17.84 MPa to37.53 MPa,the impact strength was not obvious change,but the transparency decreased from92.3%to 89.8%.The LOI value of the crosslinked copolymer decreased from 29.0%to 24.5%with the increase of the ratio of St,and the combustion grade was reduced from V-0 to V-1rating.