Effect of temperature on the volume of leather and collagen in water

Abstract

The coefficients of cubical expansion of 10 tannages of leather and tendon collagen have been measured by using water as the confining liquid. The results, calculated for dry leather of density 1.560 g/ml, show that an average coefficient of 540X10~/°C applies for collagen and all leathers except chrome-vegetable leather, the coefficient of this tannage being 340X 10~/°C. These averages have a reproducibility indicated by standard deviations of 13X10-/°C and 37X10-/°C, respectively. The or transition temperature is a band rather than a sharp point on the temperature scale. During apparent shrinkage, an increase in real volume of approximately 1 percent occurs. This increase in volume is irreversible, but the thermal expansion below the transition range is nearly completely reversible. The rate of expansion during transition of collagen follows the law of a firstorder reaction. The results are interpreted as indicating that the shrinkage does not occur at a characteristic temperature but is a rate process. The transition may be pictured as a change of state possibly coupled with a reaction.