| Polydicyclopentadiene(PDCPD)is an engineering plastic prepared by ring opening metathesis polymerization of dicyclopentadiene(DCPD)with excellent mechanical properties,low density,and high and low temperature resistance,and has been widely used in the automotive industry,medical equipment,shipbuilding,spacecraft and other large parts with complex structures.However,the all-hydrocarbon composition of PDCPD makes it extremely flammable,a large amount of smoke and harmful gases produced during combustion,which limits its wide application.Therefore,introducing flame retardant elements into the molecular chain of PDCPD through copolymerization and improving its cross-linking degree is an effective way to achieve flame retardant and high performance of PDCPD.In this paper,intrinsic flame retardant PDCPD was prepared by FROMP of phosphorus-containing flame retardant norborneyl copolymer and DCPD,and the kinetics of ROMP of DCPD with the effect of the introduction of flame retardant elements on the properties of PDCPD copolymers were investigated,and as well as the flame retardant mechanism.Then,the non-covalent interaction hydrogen bonds are introduced into the copolymerization system and study the synergistic effect with the flame retardant element.The effects of flame retardant motifs with different structures and phosphorus contents on the cross-linking network structure,flame retardant and mechanical properties of PDCPD and their synergistic effects were further investigated.On this basis,silicon containing flame retardant motif was introduced into the PDCPD molecular chain to study its effect on the front-end polymerization kinetics of DCPD and the properties of PDCPD copolymer,and the strengthening effect of NB-Si motif on the carbon layer of PDCPD copolymer was investigated.The main tasks are as follows:(1)The flame retardant monomer NB-DOPO was designed and synthesized,and the effect of NB-DOPO on the FROMP kinetics of DCPD was studied by testing the polymerization heat,frontal rate and curing degree of FROMP between NB-DOPO and DCPD.It was found that the introduction of NB-DOPO monomer reduced the f FROMP rate and heat release of DCPD.TG,DMA,tensile test and LOI test systems were used to study the regulation of NB-DOPO monomer on the performance of PDCPD.It was found that the introduction of NB-DOPO into PDCPD structure could effectively improve the flame retardant performance of PDCPD,and LOI increased from 18%to 24%,but PDCPD copolymer had the problem of weak carbon formation ability.At the same time,this copolymer reduced the crosslinking degree of PDCPD copolymer and its mechanical properties were reduced.NB-OH and NB-COOH were further introduced into the copolymerization system to improve the interaction between PDCPD molecules.The results showed that the fracture strength of the copolymer was increased to 55 MPa,and the elongation at break was increased to 80%,which was about 7 times of that of PDCPD.The T_g of the copolymer was almost equal to that of PDCPD.In addition,-OH and-COOH played the role of charcoal forming agents,which improved the carbon forming ability of the material,and the LOI increased to 28%.Under the synergistic effect of NB-DOPO and hydrogen bonding,the flame retardant and mechanical properties of the material are significantly improved.(2)Furthermore,a phosphorous flame retardant monomer NB-DHP with low resistance and flexible side group was designed and synthesized,and FROMP was performed with DCPD.The effects of NB-DHP on the properties of PDCPD copolymer were studied by TG,DMA,LOI and tensile tests.It was found that the introduction of NB-DHP improved the carbon residue and flame retardancy of the PDCPD copolymer;but with the content of NB-DHP,the breaking strength and T_g of the copolymer were still thereupon,but its elongation at break increased to 97.2%,which is more than double that of PDCPD,and the toughness of the copolymer is enhanced.When NB-DHP and NB-COOH were simultaneously introduced into PDCPD,due to the synergistic effect of-COOH and NB-DHP,the carbon residue of PDCPD/NB-DHP/NB-COOH was significantly increased,and PDCPD/NB-DHP/The LOI of NB-COOH is as high as 27.2%,and the strength and compactness of the carbon layer,and the flame retardancy of the material are significantly improved.At the same time,the breaking strength of the copolymer reaches 51.95MPa,which is 10%higher than that of PDCPD,the elongation at break increases to 80.7%,and the T_g increases to 143°C(PDCPD,T_g is 154°C).The strength and toughness of the PDCPD copolymer Both are significantly improved,and the material has an excellent rigidity-toughness balance.(3)On the basis of the above research,a silane-containing flame-retardant comonomer NB-Si was designed and synthesized.After introducing it into DCPD,the intrinsic flame-retardant PDCPD material was prepared by FROMP.DMA,LOI,and tensile tests were used.studied the effect of NB-Si on the properties of copolymers,and found that the introduction of NB-Si is not conducive to the ring-opening metathesis polymerization of DCPD,which makes the degree of branching,cross-linking,rigidity and toughness of the copolymer system decrease at the same time.However,the introduction of NB-Si into the PDCPD structure can significantly improve the strength and density of the PDCPD combustion char layer,and to a certain extent improve the flame retardancy of the copolymer.Figure[46]Table[28]Reference[149]... |
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