Investigation of the self-healing mechanism of poly (ethylene co-methacrylic acid) copolymers utilizing ultrasonic time dependent resonant spectroscopy

The ultrasonic resonant spectra of four different poly (ethylene-co-methacrylic acid) copolymers (EMAA copolymers) have been obtained using the Time Dependent Resonant Spectroscopy (TDRS) method. The spectra of these EMAA copolymers, developed by DuPont (commercially known as: Nucrel 925, Nucrel 960, Surlyn 8920, and Surlyn 8940), were analyzed. Evolution of resonances and the associated energy dissipation within the samples were observed over a period of 10 $\sim$ 50 hours. Results quantifying the influence of chemical properties (including molecular weight and ionic content), age, and damage mechanism on the self-healing response will be presented.