Structural Viscosity in Some Lyophilic Sols. II. Rubber Sols

The relative viscosities of sols of natural and purified rubber in benzene were measured at varying pressures, using the overflow viscosimeter. Deviations from Poiseuille's law to varying extents were found in all cases, with regions of structure and turbulence at various pressures. The limiting concentrations above which structure is evident and Poiseuille's law is not obeyed were found to be in agreement with those calculated by Staudinger on the basis of his theory of the relation between the viscosity and molecular weight of polymeric molecules. Exposure to ultra-violet light was found to decrease considerably the viscosity of a sol of purified rubber.