Development And Application Of New Phytic Acid-based Co-flame Retardant In Polyethylene

Polyethylene（PE）is flammable with many droplets and smoke during combustion,which seriously limits its application in the safety field.Although a large number of flame retardants have been used to improve the fire safety of PE,there are still a lot of problems need to be treated,such as low flame-retardant efficiency,extensive additions,and poor compatibility.Notably,the vast majority of flame retardants are still mainly derived from non-renewable petrochemical resources.Therefore,the development of sustainable bio-based flame retardants has become the focus of environmental protection flame retardants.In this thesis,the bio-based flame retardants systems were constructed for the flame-retardant modified PE,the relationships of the structure-performance and dose-effect between the bio-based flame-retardant system and PE composites were established,also the flame-retardant mechanism was demonstrated.The main results are as follows:（1）An all-bio-based flame retardant（PATAP）for phytic acid substrate was constructed,and the optimum conditions of its preparation and its application in PE were discussed.The results showed that the optimized preparation conditions of PATAP were as follows:the ratio of phytic acid（PA）to 2,4,6-triaminopyrimidine（TAP）was 1:8,and the reaction time was conducted for 48h at 120℃.The initial decomposition temperature(T_5%)and the residual carbon content at 800℃of PATAP respectively were 252.7℃and 33.6%,implying excellent thermal stability and carbon formation ability.With 25wt%PATAP addition,the thermal degradation and combustion behavior of PE/25PATAP composite were significantly improved compared to neat PE.The residual charring content at 800℃of PE/25PATAP composite was increased by 7.1%,while the peak heat release rate（p HRR）of the composite was decreased by 47%.Unfortunately,there was little effect on the ultimate oxygen index（LOI）and UL-94 test level of PE composites within PATAP,even specially since there are some adverse effects on the mechanical properties of the composites.（2）A novel highly efficient phosphorous flame retardant（MPT）was prepared and surface-treated,and then its effect on flame retardant and mechanical properties were explored in PE applications.The results showed that the systhesized 6A-MPT had excellent thermal stability(the T_5%was337.3℃).When 18wt%6A-MPT was added,the PE/6A-MPT18 composite passed the UL-94 test V0level,increased the LOI value to 37%,and decreased the peak heat release（p HRR）and total heat release（THR）by 41%and 52%,respectively,thanking to the vapor-phase flame-retardant effect.Compared with the PE/PATAP composite,the mechanical properties of PE/MPT increased.Although the tensile strength of PE/6A-MPT18 composites was decreased by 22%,compared with that of neat PE,indicating that the PE/6A-MPT18 were still adequate for the application.（3）Synergistic bio-based flame-retardant system with fire performance enhancement was fabricated.The effects of different metal ions and synergistic flame-retardant systems were explored on PE fire performance,thermal stability,combustion behavior and mechanical properties.The results showed that the PE composite with the compound（the mass ratio of PATAP and 6A-MPT was 1:5）could pass UL-94 V2 level.What`s more,the performance of flame retardancy for PE composites with PATAP chelating metal ions was further improved.The PE/PM5-Cu,PE/PM5-Fe and PE/PM5-Zn composites all reached UL-94 V0 level,and PE/PM5-Fe exhibited great LOI value of 35%.Compared with PE/PM5,PE/PM5-Fe possessed the best thermal stability with T_5%of 315.3°C,and the reduced p HRR and THR of PE/PM5-Fe,which was attributed to its excellent ability of char formation.Finally,the PE/PM5 composite showed the best flame retardancy and mechanical properties,with a 20%increase in impact strength and 27%increase in elongation at break compared to PE/6A-MPT20,because of the good dispersion of the compounded flame retardant.