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Hydroacoustic transducers are devices capable of converting mechanical energy from acoustic waves into electrical energy, and vice versa, through piezoelectric elements connected to electronics that need to be protected from contact with the water. This tightness is provided by the encapsulation of the transducers with elastomers. The use of fillers and chain extenders are known to promote a barrier for water diffusion, but it would inevitably change the other properties of the elastomer. Thus, this work aims to evaluate the effects of filler and chain extender addition on the properties of polyurethane elastomers (PUR) for this application. Thermogravimetric, thermomechanical, glass‐rubber transition temperature, hardness, and dielectric loss analyses are performed. It is observed an increase in the dielectric loss, hardness, and thermal stability with the addition of mineral fillers and carbon black. The addition of chain extender promoted a greater hardness in the final elastomer, but has no measurable effects on the dielectric loss, and decreased the thermal and dimension stability with temperature. Glass‐rubber transition temperatures remain in the range from –78 to –80 °C, which is in the acceptable range for the application as encapsulants.

O objetivo deste trabalho foi a obtenção de Materiais Absorvedores de Radar (RAMs) para a faixa de freqüência de 2,6 a 4,0 GHz (banda S). A carga magnética adicionada na proporção de 80% em peso à matriz de policloropreno consistiu de uma ferrita de Ni-Zn. O compósito, com espessura de 6 mm, apresentou um bom desempenho como RAM para toda a faixa de freqüência analisada com absorção de microondas superior a 96,9% (-15 dB) e com absorção máxima de 99,5% (-25 dB) em 3,2 GHz, viabilizando sua aplicação como revestimento externo em plataformas militares, segundo o ensaio de névoa salina.

No abstract