The Carbonization And Application Of Chemicals Containing Deoxybenzoin And Phosphorus

In this paper,it will be focused on the synthesis and carbonization mechanism of two deoxybenzoin and phosphorus containing materials?4,4-bishydroxydeoxybenzoin-polyphosphonate?BHDB-PPN?andBis?2,6-dimethyl-4-?2-phenylacetyl?phenyl?phenylphosphonate?BDPP??and its applications as flame retardants and carbon material in polymer industry.It was successfully synthesized and characterized of BHDB-PPN and BDPP.BHDB-PPN was polymerized through the condensation reaction between 4,4'-bishydroxydeoxybenzoin and phenylphosphonic dichloride and its chemical structure was confirmed by the IR and NMR spectra.It was indicated from the TGA and DTG that BHDB-PPN shows 50%char yield rate at800 ^oC and demonstrated a two-step degradation model.The GC-Mass analysis demonstrated that these two-step decompositions were related to the release of phenol and benzene respectively.BDPP was successfully prepared through an economic synthesis route with two steps.At first,2,6-dimethylphenol reacted with phenylacetyl chloride to form 1-?4-hydroxy-3,5-dimethylphenyl?-2-phenylethanone?HDP?;then,HDP continued to react with phenylphosphonic dichloride to form BDPP.The chemical structure of BDPP was confirmed by the NMR spectrum;TGA and Microscale combustion calorimeter demonstrated that BDPP exhibited an 26%char yield rate at800 ^oC,an initial thermal degradation temperature of 344 ^oC and a heat release capacity of 161J/?gK?.It was proposed of a new thermal degradation model and charring mechanism of BHDB-PPN through the TG-FTIR analysis of degraded products.The proposal degradation model demonstrated that that the radical termination reaction of benzyl group played a critical role in the high char yield rate.The benzyl group radical obtained from the cleavage of carbonyl-methylene C-C bond was more thermal-dynamically stable and declined to couple with other free radical to form a big framework which was going to form the char by cross-linking,de-hydrogen and de-oxygen reactions and then to increase the char yield rate of BHDB-PPN and BDPP significantly.It was found of a new method to increase the char yield rate of BHDB-PPN.The introduction of 1%and 2%aluminium diethlyphosphinate?AlPi?to BHDB-PPN increased 8%and10%char yield rate of BHDB-PPN at 800 ^oC respectively.The increase of char yielded rate might be attributed to the reaction among the degraded products from AlPi and BHDB-PPN to form stable intermediates which increased the activation energy of cleavage of P-C bond in the BHDB-PPN and reduced the release of benzene to the gas phase.The diethlyphosphinate radical degraded from AlPi might react with the intermediates decomposed from BHDB-PPN to form new phosphorus rich chemical structure.On one hand,the exposed P-C bond in the intermediate radical might be protected by the formed di-phosphorus containing chemical structure through radical termination reaction and became more difficult to break during the heating process;on the other hand,phosphorus was inclined to form more stable di-phosphorus or poly-phosphorus contained structure which might expedite the charring process of BHDB-PPN and then reduce the release of benzene to the gas phase.It was found that AlPi/BHDB-PPN blend was an effective flame retardants package in Poly?butylene terephthalate??PBT?resin.Thanks to the synergistic flame retardant effect between AlPi and BHDB-PPN,the PBT/AlPi/BHDB-PPN blend showed a robust UL 94 V0 rating without dipping and low hear release rate which were attributed to the chemical reaction between AlPi and BHDB-PPN favored the formation of char layer significantly.The PBT/AlPi/BHDB-PPN blend also exhibited high mechanical performance due to the good miscibility between BHDB-PPN and PBT resin.It was therefore concluded that AlPi/BHDB-PPN flame retardant package was a good candidate for industrial application in PBT composite.BDPP not only exhibted a good flame retarded property in Poly?trimethylene terephthalate??PTT?resin but also improved the melt stability and processing capability of PTT/BDPP blend.The introduction of 5.0%BDPP to PTT resin increased the LOI from 22.5%to 25.0%and showed about a 24.0%reduction of total heat release?THR?in comparison to neat PTT.The char yield rate and cone calorimeter analysis indicated that the improvement in flame retardant properties might be attributed to the synergistic char formation mechanism occurred in the condensed phase and flame inhibition mechanism in the gas phase.PTT resin with 5.0%BDPP addition not only exhibited a 30%decrease in melt viscosity without the reduction of molecular weight but also demonstrated a significant melt stabilization at high temperature in comparison to PTT resin.The filtration analysis revealed that 5.0%BDPP achieved a good dispersion in the PTT matrix resin.Benefited from the reduction of the melt viscosity and improvement of melt stability,the PTT/BDPP?95/5?blend could be processed as fiber at lower temperatures to achieve better tensile strength and elongation compared to neat PTT fiber.Carbon material prepared from BHDB-PPN and BHDB-PPN/AlPi were introduced to PTT resin to improve the electrical conductivity of the PTT blend.It was found that the char yielded from BHDB-PPN at 600^oC was mainly consisted of graphite sp² carbon material.The introduction of 1%AlPi to BHDB-PPN worked to increase specific surface area?BET?of the carbon material because of the formation of some nano-scale porous structures.This might be attributed to the introduction of AlPO₄ which was generated from AlPi during the carbonization process and embedded as defects in the continueous graphite net.Carbon material prepared from BHDB-PPN/AlPi?99/1?(C_BHDB-1)was introduced as an electricallly conductive additive into PTT resin and demonstrated a better electrical conductivity in PTT resin in comparison to commercial electrical conductive carbon black due to the improved BET.It was prepared of a PTT blend with high toughness and low volume resistivity through the introduction of a dynamic cross-link toughener and the C_BHDB-1 carbon material with high BET.It was found that the introduction of EMMA-GMA/EMAA-Zn?4/1?increased the toughness and electrical conductivity significantly in PTT/C_BHDB-1HDB-1 blends.On one hand,this cross-link toughener with rich epoxy groups was proved to be an effective impact modifier in PTT/C_BHDB-1 blend,which was because the zinc ion in elastomer catalyzed the reaction between epoxy and end groups of PTT resin to promote the interfacial compatibilization between PTT matrix and the toughener phase and to form homogeneous dispersed size of elastomer phase;on the other hand,as the exist of chemical cross-links and the high melt viscosity of the cross-link EMMA-GMA/EMAA-Zn?4/1?toughener,the C_BHDB-1 was inclined to disperse in the PTT continueous phase alone during the twin screw extrusion and injection molding,which helped to increase the electrical conductivity efficiency of C_BHDB-1 in the PTT blends.