Biodegradation of chemically modified gelatin films in soil

Gelatin films that had been chemically modified (crosslinked with formaldehyde, glyoxal, glutaraldehyde, hexamethylene diisocyanate, butadiene diepoxide, or diepoxyoctane) were tested for their biodegradability by soil burial testing in a laboratory environment under temperature and humidity control. The relationship between weight loss and time of biodegradation showed a linear behavior for all the samples, but the rate of biodegradation showed a dependence on the type of crosslinking agent. The most stable films were those crosslinked with aldehydes, and these biodegraded by the 10th day. The samples crosslinked with hexamethylene diisocyanate and diepoxides completely biodegraded by the fourth and sixth days, respectively. It was shown that the rate of biodegradation depended on the density of crosslinking, which was calculated by a modified Flory-Rehner equation. The biodegraded samples showed considerable changes in the fingerprint region of FTIR spectra, and, thus, these spectra could be used for evaluation of the soil burial biodegradation of chemically modified gelatin samples. (C) 2000 John Wiley & Sons, Inc.