In EMC test chambers, microwave chambers, absorbing materials play a key role in suppressing reflections and reducing interference. Two base materials are widely used: PU (polyurethane) foam and EPP (expanded polypropylene). Compared to traditional PU materials, EPP absorbers feature comprehensive structural and performance upgrades：

1.Excellent moisture resistance

EPP boasts an extremely low water absorption rate. It will not undergo hydrolysis or powder over time—even in high-humidity environments—ensuring long-term stability of electromagnetic performance and a clean lab environment.

2.Superior Weatherability

PU materials tend to yellow and harden over long-term use, whereas EPP offers superior weather resistance.

3.Low-carbon shedding

PU absorbers are commonly made by impregnation, Over long-term use, vibration, or cleaning, it can shed as dust, which degrades electrical performance. In EPP absorbers the absorbing agent is generally combined with the base material during the molding process. It is distributed more evenly and bonded more firmly, so electromagnetic performance declines more slowly.

4.Lower Total Cost of Ownership

The extended lifespan significantly reduces ongoing maintenance hassle and frequency of material replacement, delivering long-term economic value to clients.

Selection Guidance

Each material has its strengths. PU absorbers feature a mature manufacturing process, lower cost, and good broadband performance, and they can serve for many years in dry, stable chamber environments. EPP absorbers are better suited to high-temperature and high-humidity conditions, or complex operating environments. When selecting an absorber, also consider flame-retardant rating, operating frequency range, and installation method.