Stress relaxation studies of chemically crosslinked gelatin films

Abstract

AbstractStress relaxation, carried out in 85 : 15 methyl alcohol–water mixture at 60°C., of gelatin films crosslinked with oxystarch or difluorodinitrobenzene may be represented by the sum of three exponential rates of stress decay. Fresh formaldehyde‐crosslinked films relax rapidly and only require two such terms. The second term is shown to be due to the breaking of crosslinks. All excepting 10% of the broken crosslinks do not re‐form in unstressed positions as the formaldehyde is easily able to diffuse out of the layer. This 10% is suggested as being due to crosslinks involving a histidine residue. A large percentage of the broken oxystarch crosslinks do re‐form because the oxystarch is not easily able to diffuse out of the layer.