DEGRADATION OF TRAGACANTH BY HIGH SHEAR AND TURBULENT FORCES DURING MICROFLUIDIZATION

The mechanical degradation of tragacanth during exposure to microfluidization (Microfluidizer M110T, 23-degrees-C, modified high-pressure pump) was studied. Degradation was studied at inlet air pressures of 40, 60 and 80 psi which correspond to approximate pressures within the interaction chamber of 7500, 12 500 and 17 500 psi, respectively. It was observed that as exposure time to the turbulent and shear stress forces imposed by the Microfluidizer(R) increased, intrinsic viscosity estimates decreased. Intrinsic viscosity decreases were correlated to apparent changes in the viscosity average molecular weight using the equivalent sphere model. Microfluidization-induced degradation was found to be first order in accordance with the Harrington Zimm modification of the random scission model for the mechanical degradation of polymers. At all three exposure pressures, tragacanth appeared to undergo shear degradation which required two distinct apparent degradation rate constants to describe the kinetic behavior. Plausible explanations are presented for the observed biphasic behavior.