Preparation Of Phytic Acid Metal Salt And The Synergistic Effect With IFR For The Flame Retardant Performance Control Of PLA

Polylactic acid(PLA)is a new type of material with excellent biodegradability and biocompatibility,and is used as packaging materials,biomedicine,and other fields.However,the limiting oxygen index(LOI)of PLA is only 18-21%,and its application in aircraft interiors,electronic appliances and other fields was limitted by its flammable characteristics limit.Therefore,in order to maintain the environmently friendly nature of PLA,the development of halogen-free environmentally friendly flame retardants for flame-retardant modified PLA has always been a research hotspot.The traditional intumescent flame retardant(IFR)have excellent halogen-free and non-toxic flame retardant effects.But in order to achieve excellent flame retardant effect requires a large concentration of IFR.Meanwhile due to the poor compatibility of IFR and the material,it will inevitably affect other properties of the material.Therefore,the flame retardant efficiency of traditional IFR needs to be improved urgently.At present,the major direction of IFR development is to improve the overall flame retardant efficiency by the synergist.Therefore,it can improve the flame retardant properties of the material at a lower concentration.Firstly,different phytic acid metal salts were prepared by reacting phytic acid with metal ions that catalyzed the carbon formation of IFR.The synergistic effect of phytic acid metal salt and IFR on flame retardant is used to modified PLA.The study shows that when the total amout of the flame retardants is 15 wt%;and the addition of nickel phytate,barium phytate and aluminum phytate is 4 wt%,2 wt%and 2 wt%,respectively,it can make PLA achieve the UL-94 V-0 level,and the LOI of PLA was increased to 31.6%,31.0%and 30.6%respectively.Secondly,since nickel phytate can minimize the amount of IFR and maintain the best flame retardant performance,the flame retardant PLA process was studied and the flame retardant mechanism was revealed.The study found that when the total amount of nickel phytate and IFR is 15 wt%,as the amount of nickel phytate increases,the LOI of the flame retardant modified PLA increases first and then decreases.The LOI of PLA/4Ni/11IFR composites with 4 wt%nickel phytate and 11 wt%IFR reached the maximum,31.0%and also reached UL-94 V-0 level.At the same time,the cone calorimetry analysis showed that the the peak heat release rate(PHHR)and total heat release(THR)of PLA/4Ni/11IFR were 138.6 kW/m2 and 51.7MJ/m2,which were decreased by 62.4%and 10.2%respectively compared to Virgin-PLA.Its residue char was increased from 0.1 wt%to 12.6 wt%.The nickel phytate and IFR shows excellent synergistic effect on flame retardancy.The study of its flame retardant mechanism shows that during the combustion process,the nickel and phosphorus of PLA/4Ni/11IFR will play a role in catalyzing the crosslinking of IFR into carbon in the condensed phase.These residue char have a high degree of expansion and been more perfect,they can play an excellent role in flame retardant of the condensed phase.In addition,thermogravimetric infrared analysis shows that the presence of nickel phytate makes the crosslinking of IFR more efficient and faster.During the combustion process,a large amount of incombustible gas and phosphorus-containing products are released to play part of the gas-phase flame retardant effect.Finally,in order to further improve the flame retardant efficiency of nickel phytate synergy IFR,The flame retardant system(PA-Ni@N-APP)was prepared through the combination of nickel phytate,meglumine and ammonium polyphosphate(APP)in self-assembled method.It was used to improve the flame retardancy PL A.Research shows that when 14 wt%was added to PLA,its LOI can achieve 31.5%and also reach V-0 level;its PHHR and THR have decreased by 50.0%and 55.9%,respectively.The PA-Ni@N-APP has excellent flame retardant performance.The result of its flame retardant mechanism shows that during the combustion process,the nickel phytate contained in PA-Ni@N-APP can more effectively promote the cross-linking of N-APP to carbon.On the one hand,the residue char have a higher degree of expansion and been more perfect,which enhances the flame retardant effect of the residue char to isolate heat and gas transfer;On the other hand,the cross-linking of N-APP will produced a large amount of incombustible gases and phosphorus-containing products.These products can dilute or quench the free radicals in the combustion chain reaction.The gas-phase flame retardant effect make the overall flame retardant effect very excellent.