DIFFUSION MEASUREMENT OF TRITIUM LABELED POLYSTYRENE IN POLYMER BULK - EFFECT OF MOLECULAR-WEIGHT ON DIFFUSION-COEFFICIENT

The diffusion coefficients of polystyrene in polymer bulk were measured at 150°C by a radioactive tracer method over the range of molecular weight 1.10 x 1051.80 x 106 for active polymer and 4.00 xl03-1.80xl06for inactive base polymer. The effects of molecular weight on diffusion coefficients are discussed from the experimental data obtained in this work. For one-component systems, it was disclosed that Bueche’s well-known relationship of diffusion coefficient, D, with viscosity, ŋ, and temperature, T, i.e., Dŋ/T= constant, did not hold over the range of large molecular weight. As for binary systems, it was shown that diffusion coefficients at constant molecular weight of active polymer, Mp1,in inactive base polymer of molecular weight, Mr2, were proportional to Mp2-1.7 when Mp2was smaller than a critical molecular weight for diffusion, MD,beyond which diffusion coefficients were constant. It was also shown that diffusion coefficients were proportional to Mp1-1.0in the range of this work. © 1979, The Society of Chemical Engineers, Japan. All rights reserved.