Study On The Preparation And Performance Of Aluminum/PTFE Composite Materials

Aluminum(Al)is widely used in energetic material formulations because of its high reaction heat,yet only a limited part of the energy can be utilized during the aluminum oxidation process due to the ignition delay and insufficient combustion.Polytetrafluoroethylene(PTFE)has a high fluorine content of 75wt%and can react with aluminum forming Al F₃,improving the performance and energy effectiveness of the aluminum.Based on this,PTFE was employed as the coating material and mechanical activation-sintering method was developed to prepare Al/PTFE composites.The research mainly focused on the preparation parameters,modification effects and safety performance of the composites,which providing a strategy for its efficient application in energetic material formulations.The main research work and results were as follows:Firstly,the technical preparation route of the Al/PTFE composites was designed.The surface of Al was activated by pretreatment.Mechanical activation was then carried out to achieve the Al/PTFE composites,followed by sintering treatment aiming to modify the coating uniformity.Secondly,the influence of preparation parameters of the mechanical activation on the composite performance was studied.Four parameters,proportion,ball-to-material ratio,rotation speed and duration,were selected by designing an orthogonal experiment.By employing the maximum pressure of the combustion process as an evaluation index,the optimal parameter combination of the mechanical activation was defined:Al:PTFE ratio was 65:35,the ball-to-material ratio(BPR)was 12:1,the rotation speed was 250 rpm,and the duration was 45mins.It was also found that if no reaction was triggered within the duration,the influence degree of the four factors on performance would be ranked as follows:ratio>BPR>rotation speed>duration.Then,the effects of sintering treatment and its process parameters on the composite performance were studied.Through morphology and pressure characterization tests,it was found that the sintering treatment could effectively improve the coating uniformity of PTFE on aluminum surface,resulting in the maximum pressure and pressurization rate of the composites being increased by 12.5%and 10%,respectively.Based on this,the PTFE content and sintering temperature were further studied.The results of macro burning rate tests and molecular dynamic simulations showed that when the PTFE content was 20%?35%,the sintering treatment worked better.In addition,340°C could be employed as the appropriate temperature for PTFE sintering process.Finally,the modification effect and safety performance of Al/PTFE composites were studied.According to the analysis of microscopic morphology and macroscopic combustion performance,it was found that compared with the simple mechanical mixtures,the sample obtained by mechanical activation-sintering method exhibited better dispersibility and coating uniformity.Infrared thermal imaging and product composition analysis tests revealed that the formed Al/PTFE composites of increased contact area and shortened diffusion distance showed more sufficient combustion performance.Chemical stability test revealed that compared with the raw material,the stability of the composites was significantly improved,which providing basis and safety guarantee for the formulation application in the future.