Dynamic mechanical and rheo-optical studies of collagen and gelatin.

Abstract

AbstractThe frequency dependence of dynamic mechanical properties of rat tail tendon (RTT), enzyme‐solubilized collagen membranes (ESC), AKM‐23 dialysis membranes, and gelatin film have been measured at 110, 11, and 3.5 Hz from ‐ 160 to 220°C. RTT and AKM‐23 are devoid of a rubbery region; there are as many as six mechanical loss transitions. Gelatin and ESC membranes behave as rubbery materials above room temperature; only three tan δE peaks can be resolved for these materials. Strain birefringence was used to measure the crystalline and amorphous contribution of orientation induced by strain. Both the birefringence and the strain optical coefficient are sensitive to the amount of water in a sample. The effect of chemical swelling agents and of annealing on birefringence are described. Stress relaxation data on gelatin film were analyzed with the rubber elasticity theory to give the average number of chains per unit volume, the specific polarizability, the stress‐birefringence ratio and the average molecular weight between hydrogen bonds were calculated. The intrinsic amorphous birefringence for “wet” gelatin film is 1.25 × 10−2; it is estimated to be about 6 × 10−2 for “dry” gelatin film.