Irradiation Modification Of Polytetrafluoroethylene And Its Inorganic Composites

Polytetrafluoroethylene（PTFE）has good chemical stability,good mechanical properties and wear resistance,but its tensile strength and flame resistance is still not enough to meet the performance requirements of lithium battery reactor flame retardant partition.In this paper,γ-rays of ⁶⁰Co were used as the radiation source to improve the tensile properties and flame resistance of PTFE by irradiation modification.In addition,the properties of PTFE materials are enhanced by the addition of nano-inorganic fillers with PTFE for the preparation of composites.It is also modified by irradiation to maintain the tensile properties of PTFE composites and to improve the flame retardancy and thermal stability of the material.The PTFE materials selected in this paper are PTFE film and expanded PTFE.First,the material was modified by irradiation,and the optimum conditions for irradiation modification were sought from four aspects:irradiation atmosphere,temperature,dose and dose rate.The results showed that the tensile properties of PTFE films decreased sharply with the increase of radiation dose in air atmosphere.PTFE was dominated by irradiation degradation reactions under air atmosphere.The optimal conditions for irradiation in N₂ atmosphere are 150°C,a dose of 28k Gy and an irradiation dose rate of 14k Gy/24h.After irradiation modification,the tensile properties of PTFE film were improved,and the mechanical properties of expanded PTFE were basically unchanged and the flame resistance was improved.Secondly,inorganic nano-Al₂O₃,Si₃N₄,and Si O₂ were used to prepare PTFE films and expanded PTFE composites.For PTFE film material,the optimum addition amount of filler is 1.5wt%.Compared with the pure PTFE film the tensile properties of the composite PTFE film material with the addition of nano-Al₂O₃ and Si O₂ were reduced.The tensile strength of the PTFE film compounded with Si O₂ nanoparticles and Al₂O₃ was improved when irradiated at 150°C,28 k Gy,and 14 k Gy/24h.The tensile strength after irradiation even exceeded that of the pure PTFE film.After irradiation modification,the composite material can be improved by the addition of nanoparticles while ensuring that the mechanical properties are not affected.For the expanded PTFE material,the optimal amount of filler addition was obtained by screening at 1.0wt%.The tensile properties and the flame resistance of the materials were improved,the shrinkage rate of material area decreased after the compounding of nano-Al₂O₃,Si₃N₄ and Si O₂ with expanded PTFE at the addition amount of 1.0wt%.The flame resistance and the thermal stability of nano-Al₂O₃（1.0wt%）and Si O₂（1.0wt%）composites were improved after irradiated at 150°C,28k Gy,and 14k Gy/24h.It is suggested that the cross-linked network formed by irradiation hinders the thermal shrinkage of the composites and contributes to the maintenance of dimensional stability at high temperatures.