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An Ultrasonic Technique for Characterization of Biodegradable Polymers
An ultrasonic technique was used to measure material property change during hydrolytic degradation of a biodegradable copolymer, 50/50 poly(D,L-lactide-co-glycolide). Six groups of 3 copolymer buttons were immersed in 60℃ distilled water for 0, 1.5, 3.0, 6.0, 10.0 and 24.0 hours. A longitudinal wave generated by a 20MHz transducer and a pulser/receiver card was directed per-pendicularly to copolymer disk at 20℃. The reflected signals coming back to transducer were recorded and saved through a data acquisition board. The longitudinal wave speeds and attenuation coefficients of the disks undergoing various exposures to a water bath were calculated by the cross-correlation method nand fast Fourier transformation (FFT) of the digitized waveform data. The wave speed decreased by a factor on one third and the attenuation coefficient increased up to four times within 24 hours in the 60℃ water bath. The results suggest that the ultrasonic technique provides a useful method for the study of hydrolytic degradation of poly(D,L-lactide-co-glycolide) in a non-destructive manner.
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