Study On Preparation And Properties Of Transparency Flame Retardancy PMMA

Polymethyl methacrylate?PMMA?is a polymer with excellent optical property which commonly known as“plexiglass”.It is widely used in various fields such as aerospace,daily lighting,fiber optic communication for its excellent electrical insulation,wear and weather resistance properties.However,PMMA is extremely flammable with really high PHRR in Cone Calorimeter?1058 k W/m²?.Besides,neat PMMA has severely dripping behavior during the combustion process,which would cause serious fire risk and threat the safety of people and belongings.Therefore,it is of great significance to study flame retardancy PMMA.Blending the flame retardants with PMMA is a commonly used modify method to obtain flame retardancy PMMA.However,the transparency and the mechanical properties of PMMA were usually sacrificed for adding these flame retardants,which greatly limit the application of PMMA in optical field.The chemical copolymerization is another method which has a relatively small impact on the transparency and mechanical properties to modify PMMA.However,it often requires a series of complex chemical reactions to connect the flame retardancy element and unsaturated double bonds in one material,and it also has high economic cost which greatly limits its industrial application Therefore,developing PMMA which not only containing transparency and flame retardancy properties,but could also be operated easily are currently unresolved issues,and they are also huge challenges for flame retardancy PMMA in research.In this paper,the transparency and flame retardancy PMMA blends and copolymers were prepared by bulk polymerization.And the resultant PMMA could not only have good flame retardancy,but also possess excellent transparency.The following works have been done:1.The halogen-free flame retardant triethyl phosphate?TEP?which has good compatibility with methyl methacrylate?MMA?with cheap cost was introduced into PMMA matrix by bulk polymerization to obtain a novel kind of transparency and flame retardancy PMMA/TEP blends.The combustion behavior,mechanical properties,and optical properties of the PMMA/TEP blends were studied.The results show that the introduction of TEP has a good flame retardancy effect on PMMA,and do not affect the transmittance of PMMA.The Limiting oxygen index?LOI?of PMMA/TEP blends could be increased to 21.9%,when 20 phr of TEP was introduced,and the transmittance of PMMA/TEP blends in the visible wavelength range could be reached more than 90%,which is equivalent to that of neat PMMA.The toughness of the PMMA/TEP blends increased and the tensile strength,vicat softening temperature?VST?of PMMA/TEP blends decreased with the increasing of TEP content,since TEP playing a plasticize effect in the blending system.When the content of TEP is 15 phr,the blends has a LOI of 21.7%,a tensile strength of 43.1MPa,and a VST of 72.3?,and its transmittance in the visible wavelength range is higher than 90%.In this amount,the flame retardancy,optical,mechanical,and thermal properties of the blends can all fulfill the need of use.2.The added flame retardancy molecular TEP could not be connected to the PMMA molecular chain by chemical copolymerization because it don't contain unsaturated carbon-carbon double bonds,which resulting in the non-durable flame retardancy property of PMMA.On this basis,the flame retardant 2-hydroxyethyl methacrylate phosphate?HEMAP?was further selected as a reactive monomer to take participate in the copolymerization with MMA and a series of P?MMA-co-HEMAP?copolymers with different flame retardant contents were synthesized by radical polymerization.The results show that the LOI of the 30 phr HEMAP increased from 17.8%to 24.5%,the PHRR and Total Heat Release?THR?of the 30 phr HEMAP were significantly reduced by 40.0%and 36.2%,respectively.When 30 phr TEP is added,the PHRR and THR of the PMMA/TEP blends only decreased by 16.5%and 29.7%,respectively,indicating that the introduction of HEMAP into the PMMA matrix has an excellent flame retardant effect compared to TEP.In addition,the optical and mechanical properties of the P?MMA-co-HEMAP?copolymers were also studied.The results show that,the addition of HEMAP has no negative influence on the transmittance of the copolymers,and its transmittance in the visible light wavelength range was still maintained above 90.0%,which will not affect its application in the field of optical transparency.With the increasment of HEMAP,the tensile strength of P?MMA-co-HEMAP?copolymers increased firstly and then decreased.When a small amount of HEMAP was introduced,it could form a cross-linked structure in the bulk copolymerization system to improve the tensile strength of the P?MMA-co-HEMAP?copolymers,however,if there is too much HEMAP,it would play a plasticize effect in the system,and then resulting in the decreasment in copolymers'tensile strength.In addition,HEMAP has a toughening effect on PMMA.The impact strength of 30 phr HEMAP copolymer could be increased to11.1k J/m²,which is 45.1%higher than that of neat PMMA.Besides,the HEMAP could significantly improve the anti-static properties of P?MMA-co-HEMAP?copolymer.And the surface resistance of the 20 phr HEMAP could be reduced down to 10¹⁰?which could achieve anti-static effect.This is due to the phosphate groups in HEMAP,which could absorbe moisture in air to form a conductive film on the surface of the copolymer,which reduced the surface resistance of the copolymers.3.The tensile strength of the binary copolymer was decreased withplenty HEMAP,and the flame retardancy property achieved by pure phosphorus flame retardant need to be further improved.On the basis,a series of P?MMA-co-HEMAP-co-DMAA?terpolymers was prepared using HEMAP,N,N-dimethylacrylamide?DMAA?and MMA as monomers through exploring the best molar ratio of phosphorus and nitrogen in terpolymer?HD?.The optical property of the terpolymers was tested,and it was found that the transmittance of the terpolymer in the visible light wavelength range remained above 90.0%,and its haze was less than 4.0%.The LOI of the 30 phr HD terpolymer could be increased to 25.0%,which was 41.2%higher than that of neat PMMA,indicating that the HD could greatly improve the flame retardancy of PMMA.What's more,since HEMAP and DMAA were both multifunctional monomers,and they made the crosslinking structure of the system more perfect,so the introduction of HD could enhance the tensile strength and impact strength of the terpolymer,which further expanding its application range.