Research On 1-9GHz Thermoplastic Wave Absorbing Material

Wave-absorbing materials have been widely used in modern aerospace,fighter stealth and electromagnetic anti-jamming of electronic equipment.However,with the popularity of wave-absorbing materials,when they are used in some equipment with high power and high working environment temperature,the designability,mechanical properties,temperature resistance and weather resistance of traditional wave-absorbing materials can not meet the requirements.Thermoplastic materials have become an ideal matrix for composite wave-absorbing materials because of their excellent properties,but at present,the preparation technology of thermoplastic composite wave-absorbing materials is not complete and needs to be further improved.In order to solve the above problems,the preparation process of carbonyl iron powder / polyether ether ketone（CIPs/PEEK）was optimized by analyzing the effects of extrusion parameters and filler content on the dispersion uniformity and thermal properties of the composites.The oxidation problem of carbonyl iron powder in the preparation of composites was solved by coating method,and based on Maxwell-Garnett formula,the corresponding relationship between CIPs/PEEK and CIPs/Paraffin（paraffin）was found,which simplified the characterization of electromagnetic parameters of CIPs/PEEK.Finally,from the point of view of filler content,material thickness and multiabsorbent composite,the electromagnetic parameters of thermoplastic composites are optimized to achieve efficient wave absorption in 1-9GHz.The specific work are as follows:（1）The crystallization behavior and melting index of different grades of polyether ether ketone samples were analyzed,and the sample grades suitable for experimental research were selected.The effects of mass fraction and particle size of carbonyl iron powder on the microwave absorbing properties of 1-9GHz composites were studied,which laid a foundation for the study of electromagnetic properties of thermoplastic composites.（2）The effects of extrusion speed and extrusion temperature on the packing uniformity of thermoplastic composites were analyzed.It was found that the cavity and agglomeration of the masterbatch were reduced when the rotational speed was 30r/min and the extrusion temperature was 370℃-375℃.Under these conditions,the effects of carbonyl iron powder content on the extrusion state,melting index,thermal stability and density of CIPs/PEEK were studied.It was found that the increase of carbonyl iron powder content would lead to the decrease of CIPs/PEEK melting index,the decrease of initial decomposition temperature and the increase of internal cavity in the masterbatch.（3）The corresponding relationship between CIPs/PEEK and CIPs/Paraffin is found by Maxwell-Garnett formula,which simplifies the characterization process of CIPs/PEEK electromagnetic parameters.After the carbonyl iron powder was coated with silane coupling agent,the oxidation weight gain of carbonyl iron powder was reduced to4% in the temperature range of 365-390℃.Effectively improve the working temperature point of the composite.Finally,the absorbing properties of the composites in the 1-9GHz frequency band are controlled by mixing a variety of absorbing fillers.In a word,the preparation process of thermoplastic composites and the waveabsorbing properties of 1-9GHz were deeply studied in this thesis.The extrusion process of CIPs/PEEK was optimized,the characterization process of electromagnetic parameters of CIPs/PEEK was simplified,and the working temperature and oxidation resistance of CIPs/PEEK and wave-absorbing properties of 1-9GHz were improved.