Elastomeric Polypeptides as Acoustic Absorbers for Navy Applications

摘要

Elastic protein n-based polymers comprised of repeating pentapeptide sequences, (GXGXP)(n), exhibit mechanical resonances that have been observed to date with frequency maxima near 5 MHz and 3 kHz. Because the 3 kHz resonance is in the middle of the acoustic frequency range, the purpose here is to substantiate the relevance of the 3 kHz resonance to acoustic absorption and to demonstrate means of improving mechanical properties for the sound absorption application. Previously reported loss factor data in the 100 Hz to 10 kHz range is substantiated by relevant but distinctly different measurements of loss shear modulus and loss permittivity. Furthermore cross-linking approaches are reported that result in increase elastic moduli by an order of magnitude to 4 x 10(exp 6) Pa at 20% strain and that increase break stress by two orders of magnitude to 1. 3 x 10(exp 7) Pa while exhibiting break stain values of several hundred per cent.