Composite polymethacrylimide foam wave absorption material

Abstract

The invention discloses a composite polymethacrylimide foam wave absorption material which is prepared by the following steps: (1) performing surface treatment on a wave absorber, namely uniformly mixing the wave absorber and a surfactant with a solvent, ultrasonically processing, drying to remove the solvent, and breaking and grinding to obtain a wave absorber subjected to surface treatment; (2) preparing expandable polymethacrylimide resin particles; (3) preparing the composite polymethacrylimide foam wave absorption material. The material is good in wave absorption performance, heat resistance and mechanical property, can be used for avoiding the defects of complex process, material waste and the like caused by a process that the material is machined to obtain a complex shape, can absorb electromagnetic waves to prevent electromagnetic wave interference, can be applied to the aspects of medical appliances, household appliances, electronic products, high-rise buildings, communication equipment, measurement equipment and the like, also can be used for stealth of various aircrafts, and has wide application prospect in the civil or military field.

Description

technical field [0001] The invention relates to a polymethacrylimide composite foam wave-absorbing material. Background technique [0002] Polymethacrylimide foam (PMI) is a cross-linked, uniform pore size distribution foam with excellent structural stability and high mechanical strength. Polymethacrylimide foam has higher specific strength, specific modulus, heat resistance and heat and humidity resistance than other polymer foam materials, as well as better high temperature creep resistance and dimensional stability. Its outstanding heat resistance and excellent creep resistance at high temperatures enable it to withstand the high temperature curing process conditions of thermosetting resin composite materials such as epoxy and Shuangma, and can realize one-time co-curing molding of foam sandwich and prepreg, It can be widely used in the manufacture of composite material foam sandwich structures. In addition, due to the high closed cell rate, uniform pore size distributi...

AI Technical Summary

Problems solved by technology

[0005] Chinese patent application No. 200710159605.5 discloses a kind of expandable particles for the production of polymethacrylimide foam materials, due to the nature of this type of polymer, the foam particles cannot form a tight bond during the foaming process , only loose foam particles can be obtained without overall mechanical strength; while there is no wave absorbing agent added inside the PMI particles, only the wave absorbing agent is added in the gaps of the PMI foam particles, and the types of wave absorbing agents added in the gaps are very few, resulting in its absorption Wave frequency range and absorbing efficiency are low

In addition, without surface treatment of this type of wave absorbing agent, the wave absorbing agent cannot be evenly dispersed on the surface of PMI foam particles, which affects the actual application effect of this type of wave absorbing material

[0006] The Chinese patent application with the application number 201010180775.3 uses crushing and sieving to obtain resin particles, resulting in the production of a large amount of resin powder with very fine particles. Since the foaming agent contained in the fine particles is more likely to overflow from its surface, the fine particle resin The expansion rate of the powder is very low, too fine powder cannot be foamed, and the specific surface area of ​​the particles is large, and more binders are needed to obtain functional foam, which increases the density of the foam and also causes a large amount of fine particle resin powder. waste

[0007] The Chinese patent application with the application number 200810031468.1 uses the method of using functional powder additives in the polymerization raw material mixture. Due to the chemical characteristics, viscosity characteristics, density characteristics of the raw materials, and the characteristics of free radical polymerization, the types of additives, The amount used is limited, resulting in limited absorption of functional foams obtained in this way

Similarly, it does not carry out surface treatment on this type of absorbing material, and it cannot make the absorbing material evenly dispersed in the PMI system, so that the absorbing performance of each part of the PMI foam material is greatly different, which limits the use of this type of absorbing material. Practical Applications of Wave Materials

[0008] Chinese patent application CN200910102124.X discloses a preparation method of a wave-absorbing PMI foam sandwich structure composite material. This preparation method has the following defects in the actual use process: first, the added wave-absorbing agent has not been surface-treated, and the absorbing When the wave agent is added in a small amount, the wave-absorbing performance is poor; when it is added in a large amount, it often has a great influence on the polymerization reaction, which makes the foamable foam material not evenly foamed or even normally foamed.

In actual use, the foam materials synthesized by this method often have defects such as insufficient foaming, easy settlement, poor mechanical properties, poor wave-absorbing performance, and low wave-absorbing strength.

Moreover, there are fewer types of absorbing agents added, which only have absorbing properties in certain frequency ranges, and do not have wider frequency absorbing properties.

The wave-absorbing performance of the foam sandwich structure is not uniform, and most of the wave-absorbing agent is concentrated on a certain interface, and the test results in different directions are quite different. If the structure is cut and tested, it will be found that the The absorbing performance is also very different

[0009] It can be seen from the above that polymethacrylimide foam materials with good mechanical properties and good wave-absorbing properties are relatively scarce at present.