Functional Modification Of Aramid Ⅲ Fiber And Study On The Microwave Absorbing Properties Of The Products

Absorbing material refers to the electromagnetic wave incident to the absorber into heat energy or other forms of energy,in the military stealth and civil electromagnetic radiation has a wide range of applications.Polypyrrole（PPy）,a member of the conductive polymer family,has become a kind of lightweight absorbing material due to its excellent electromagnetic loss ability,outstanding lightweight characteristics and easy preparation.At present,in the field of stealth design of military aircraft,ballistic missiles and other airborne weapons,not only the strong absorption efficiency of absorbing materials is required,but also the improvement of their lightweight and mechanical properties is increasingly required.Although PPy is an excellent lightweight absorbing material,it cannot be applied in the field of stealth design of space flight weapons requiring mechanical and mechanical properties.Based on this,many research teams have carried out research on the synthesis of PPy on the surface of fiber materials.Among fiber materials,aramid Ⅲ fiber（F3 fiber）has excellent mechanical properties,dielectric properties and heat resistance,which is very conducive to being used as a structural stealth composite material.Therefore,F3 fiber can be functionalized and PPy can be synthesized on the surface of F3 fiber,which is highly likely to obtain composite absorbing materials with excellent absorbing performance,lightweight and outstanding mechanical and mechanical properties,which will accumulate preliminary foundation for further promoting the application of such composite products in the field of space flight weapons and equipment.In this paper,PPy and Fe₃O₄ were used as functional particles and F3 fiber as matrix material,and PPy/F3 and Fe₃O₄-PPy/F3 products were prepared by simple in situ polymerization and one-step polymerization respectively,and the electromagnetic wave absorption properties of the products were mainly studied.The results are as follows:（1）The in-situ synthesis method was used to realize the loading of PPy on the surface of aramid Ⅲ fibers（F3）,and the PPy/F3 product was obtained.The effect of reaction temperature on the wave-absorbing properties of composite fiber products was discussed.The results show that with the increase of the reaction temperature,the absorbing properties of the products show a trend of increasing first and then decreasing.Its minimum reflection loss is-20 d B at 13.5 GHz,the matching thickness is 3 mm,and the corresponding effective absorption bandwidth is 7.3 GHz.（2）In the previous chapter,the PPy/F3 prepared at a temperature of 25℃has the best absorbing performance.Therefore,in this chapter,the temperature was selected as25℃,and the PPy/F3 product was prepared by the in-situ synthesis method.The influence of the concentration of Py monomer on the absorbing properties of the composite product was discussed 0.04 mol/L.On this basis,the effect of the dopant（PTSA）concentration on the absorbing properties of the composite product was investigated,and the dopant concentration to obtain the optimal absorbing properties was 0.04 mol/L.The results show that under the optimal synthesis process in this experiment,the prepared PPy/F3 fiber product has the most excellent wave absorption performance,the minimum reflection loss is-27 d B at 15.9 GHz,and the matching thickness is 3 mm,corresponding to the effective The absorption bandwidth is 6.4 GHz.（3）Through the work in the first two chapters,it is found that although PPy/F3 has excellent wave absorbing ability,there may be a problem of poor impedance matching between a single PPy load and the F3 surface.Therefore,a one-step method is used to introduce Fe₃O₄into PPy/F3.In the product system,Fe₃O₄-PPy/F3 was prepared.The effect of ammonia concentration on the wave-absorbing properties of composite products was discussed.The results show that compared with the PPy/F3 in the previous two chapters,it is found that when Fe₃O₄ nanoparticles are introduced into the PPy/F3 product system,the loss ability of the product to electromagnetic waves is significantly improved,and Fe₃O₄-PPy/F3 can achieve less than-10 d B.The reflection loss value,when the addition amount of ammonia water is 20 m L,the prepared product has the best absorption performance,the minimum reflection loss reaches-44.4 d B at13.4 GHz,the matching thickness is 3.5 mm,and the corresponding effective absorption bandwidth is 7.3 GHz.