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With the continuous improvement of the performance requirements of wave absorbing materials, polyurethane wave absorbing sponges are no longer competent in anechoic chambers in some application fields, and a class of wave absorbing materials based on rigid foam has been deeply studied. This type of absorbing material matrix includes expanded polyethylene (EPE), expanded polystyrene (EPS), expanded polypropylene (EPP) and the like. These materials have closed cells, better mechanical strength than polyurethane, and are not easy to absorb moisture and deform. The new wave absorbing material has been added with the wave absorbing agent in the raw material production stage, and then molded to obtain the product with the required shape and performance. The whole process of material preparation is mechanized, and the product properties are stable.
Select EPP as the absorbing matrix
- Excellent heat resistance: EPE has a temperature resistance of 70-80 °C, EPS is less than 80 °C, and EPP can withstand 120 °C. Moreover, the dimensional shrinkage of EPP is less than 2% when placed at 120°C for 22h.
- Excellent mechanical properties: The longitudinal and transverse tensile strengths of EPP with a density of 0.035g cubic centimeter are 0.56MPa and 0.38MPa respectively, and at a high temperature of 120°C, the bidirectional strengths are 0.07MPa and 0.035MPa.
- Excellent environmental performance: Compared with polyurethane (PU) foam, EPP does not produce isocyanate residues that are harmful to human body, and the product can be recycled; compared with polystyrene foam (EPS), it is not used in the foaming process To HCFCs or butane, there is no adverse impact on the environment after degradation; compared to polyethylene foam (EPE), the new foaming process reduces the use of chemical blowing agents and is healthier.
Design optimization using full-wave simulation
The traditional design method of absorbing materials is to use the transmission line theory to carry out the “transmission line design method”, which only calculates the normal incidence performance and does not consider the influence of the shape of the taper.
The absorbing material adopts full-band simulation, and optimizes the calculation to obtain the structure with the best absorbing performance, which ensures the electromagnetic wave absorbing performance of the absorbing material.
Absorbance measurement using spatial scanning method
The traditional “bow box method” only measures the frequency range of 2-18GHz, and neither low frequency nor high frequency can be measured, and the accuracy is low.
The absorption rate measurement of the absorbing material adopts the self-designed “7”-shaped rocker arm structure for spatial scanning measurement, which can satisfy the multi-degree-of-freedom scanning in the ultra-wide frequency band of 0.5GHz~70GHz, and the measurement accuracy is greatly improved.
- Electrical properties: EPP has a small dielectric constant and small surface reflection. The entire material is homogeneous, with sufficient attenuation inside, and the microwave frequency band has a good wave absorption effect.
- Flame retardant properties: meet the UL94 HF-1 standard.
- Oxygen Index: >27%.
- Working temperature: long-term -50-100℃, short-term 120℃.
- Environmental protection: the raw materials are non-toxic and tasteless, no harmful gas is released, and you can rest assured from the source.
- Finished product: stable in nature and RoHS compliant.
- Physical properties: One-time compression molding, accurate size; uniform appearance color, customizable color; good product stability, no deformation.
Wide range of applications
The electrical properties of the absorbing foam are measured in a compact field anechoic chamber by the RCS method, and the quiet zone of the measurement anechoic chamber is greater than 1.5 meters. The distance between the DUT and the antenna is more than 10 meters, which meets the far-field conditions. It can provide low noise and pure electromagnetic environment for various OTA measurement anechoic chambers, PIM anechoic chambers, etc.