Study On The Flame Retardant And Anti-Aging Properties Of Polyvinyl Alcohol Films By Phytic Acid-Based Complexes

Polymers are widely used in various fields such as construction,electronic devices,industrial packaging and transportation due to their easy processing,easy availability of raw materials and advantageous physical and chemical properties.However,most polymers are highly flammable,release large amounts of heat and toxic gases during the combustion process.Therefore,once polymers are attacked by flame,there will be incalculable harm to life and property safety of people.Most of the polymer plastic raw materials are derived from petroleum cracking,such as polyethylene(PE)and polypropylene(PP)are produced by polymerizing ethylene and propylene derived from petroleum cracking.With the depletion of energy,environmental pollution problems are becoming increasingly serious,the development of recyclable,green materials are particularly important.Polyvinyl alcohol(PVA)is a green,renewable,degradable and environmentally friendly polymer.However,PVA is also extremely flammable,its limit oxygen index is only about 18%,and PVA flammability is not only a significant threat to people’s lives,health and property safety,but also limit the application in many areas.Thus,the flame retardant research for PVA is widely concerned.The traditional flame retardant method is to introduce a large number of metal hydroxides,organic compounds,halogens,etc.,which can seriously weaken the biocompatibility,mechanical strength and transparency of PVA films.At the same time,some flame retardants,such as halogens,produce carcinogenic substances during combustion,which seriously threaten human health and safety.Therefore,there is an urgent need to prepare efficient,environmentally friendly and green flame retardants for PVA.The raw materials of bio-based flame retardants come from animals and plants which can be widely obtained from nature as renewable resources.bio-based flame retardants are renewable,environmentally friendly and sustainable.The use of renewable bio-based flame retardants can not only solve the problem of toxic halogen flame retardants,but also alleviate the shortage of some non-renewable raw materials,while the use of bio-based flame retardants will not reduce the biocompatibility of PVA materials,so they can be used in more fields.Therefore,it is an urgent problem to develop an efficient,green and environmentally friendly PVA flame retardant without affecting the performance of PVA itself.Aiming at the problems of reducing the mechanical strength,transparency and biocompatibility of PVA films exhibited by the current flame retardants for PVA,this study aims to design and prepare highly efficient and green flame retardants for PVA.Generally,two different bio-based flame retardants were synthesized and prepared by using phytic acid as raw material,and the flame retardants were analyzed by using different characterization means.The flame retardant PVA composites were prepared by physical mixing and their relevant properties were tested,and the research is as follows:1.Phytic acid,as a liquid organic acid that can be extracted from plants,is widely used in flame retardant,because of its high phosphorus content.However,the flame retardant effect is not ideal when using phytic acid alone as a PVA flame retardant,so phytic acid and ethylenediamine were selected to synthesize a new phosphorus-nitrogen type flame retardant PAE to enhance the flame performance of PVA materials.The test results showed that the introduction of 15 wt.% PAE gives PVA excellent fire performance,and the values of p HRR and THR of PVA/PAE-15 composites decreased significantly by 68.1% and 31.0%,respectively.from VTF test,PVA/PAE-15 composites also show excellent UL-94 V-0 grade;the char and LOI are also improved at the same time,the analysis of the char suggested a possible flame retardant mechanism: PAE can effectively stop the flame propagation in the gas and condensed phases,thus improving the flame retardant performance of PVA.In addition,the introduction of PAE in PVA also makes the tensile strength and UV shielding of PVA/PAE composites improved.2.In order to further improve the biocompatibility and UV shielding performance of PVA composites,amino acids,a common nitrogenous compound with abundant resources and low price,were selected to prepare bio-based phosphorus-nitrogen integrated flame retardants with phytic acid.Therefore,phytic acid and creatine monohydrate are selected to synthesize the flame retardant PACR to improve the fire performance of PVA materials.The results show that when 20 wt.% of PACR is added to PVA,PVA/PACR composites showed the best flame performance,and the decrease rate of its p HRR and THR values reached 92% and 68%,respectively,compared with pure PVA.They also achieve UL-94 V-0 grade,showing satisfactory flame retardant effect,and the analysis of char layer revealed that the flame retardant PACR can catalyze the formation of continuous and dense char layer to stop the transfer of heat and oxygen to the substrate,meanwhile it can release non-combustible gases during the combustion process,increasing the height of the char layer and diluting the concentration of oxygen.After adding PACR,the mechanical properties and UV absorption capacity of PVA are improved too.Application experiments show that PVA/PACR composite film can effectively stop the oxidation of food caused by UV irradiation,so PVA/PACR composite film shows great potential in the field of food packaging.