Behavior and properties of neat and filled gelatins

The purpose of this study was to determine the mechanical properties and the atomistic structures of various gelatin hydrogels as a preliminary to using these in bioengineering applications. The hydrogels were investigated as neat materials and as particulate-reinforced composites both in the as-formed state and following cross-linking with formaldehyde and/or glutaraldehyde. The compressive modulus obtained using alumina particulates as the reinforcement was found to be enhanced significantly more than expected on the basis of considering a gel matrix to be similar to a thermoplastic one. From the electron paramagnetic resonance of a Cu(2+) probe ion implanted in these materials it was determined that the variation in the compressive moduli with Bloom indices results from a gradation in the relative weightings of two discrete coordination configurations. The cross-linking led to different coordinations following the formaldehyde vs. the glutaraldehyde treatments.