Effect of diluents on fusion temperature of the crystalline regions in plain and tanned cowhide

摘要: Melting (shrinkage) phenomena in plain cowhide were investigated by measuring the temperature at which contraction first occurred specimens containing varying amounts of ethylene glycol, formamide, phenol, and water as diluents. Similar measurements made on had been tanned with formaldehyde a vegetable tannin contained diluent. In all cases was found to increase diluent concentration decreased general accord theory melting-point depression. The melting crystallites undiluted found, extrapolation data each system zero content be about 145°C. temperatures cowhide, however, depended tanning agent employed. A value 120°C. obtained for vegetable-tanned 151° formaldehyde-tanned cowhide. former verified experimentally direct measurement. This evidence decrease crystallite stability indicates that acts observations reduces availability amorphous regions diluents either through type crosslinking and/or reduction number active sites. accounts observed elevation commonly measured shrinkage hide after tanning. addition, agents can markedly modify mechanical properties acting plasticizer or stiffening agent. heats fusion, ΔHu, diluted phenol 2200, 1600, 1800 cal./mole, respectively. However, hide, ΔHu 7200 cal./mole. values hide. Entropies ΔSu, (assuming two bonds per residue freed melting) 2.6, 1.9, 2.2 cal./deg./bond, respectively, while water, 8.5, 9.2, 9.5 cal./deg./bond. order bring entropy systems into agreement other it is necessary assume eight are melting.