Dynamic mechanical and vibration damping properties of polyurethane compositions

Abstract

AbstractA series of polyurethane compositions with varying comonomer ratio and structure, polyblends with epoxy resin, and filled systems with mica and calcium carbonate were prepared. The dynamic mechanical properties of the compositions were measured at 110 Hz using a Rheovibron. The vibration damping properties were measured using a Brüel and Kjaer damping modulus apparatus with steel strips as substrate, the polyurethane compositions as coatings, and, when used, a constraining layer of aluminum or epoxy. The damping curves by the two techniques were similar in shape. Furthermore, the damping properties of the compositions in both extensional and constrained layer configurations could be estimated from the dynamic mechanical properties. The width of the damping region in terms of the temperature range was used as a criterion for effectiveness. Very wide ranges of temperature, and hence frequency, fell within the damping region which was broadened to as much as −40–60°C by the use of bulky backbone chain polymers, by polyblending with epoxy, and by filling with mica. Mica in an extensional mode configuration could be considered as equivalent to a constraining layer for purposes of calculation. The data agree well with the general view that extensional mode damping requires a high loss modulus and constrined mode damping a high loss factor, in both cases being more effective if the storage modulus were also high.