VISCOSITY AND AXIAL RATIO OF SHELLAC

Molecular axial ratios for hard resin, soft ruin and dewaxed shellac have been calculated from viscometric data using different solvents (EtOH. PrOH and BuOH). The ratio 10.3 for dewaxed shellac has been found to be a weighted average of the values for hard resin (11.3) and soft resin (7.8).

The effect of good and bad solvents as also of solvents-precipitant mixtures on the intrinsic viscosity of shellac and the variation of this with temperature has been studied. Frain a consideration of these data in the light of Alfrey, Bartovics and Mark's theory, it has been possible to conclude that shellac molecules are not flexible.