Fluorescence measurements of the diffusion coefficient for butylated hydroxyanisole in low-density polyethylene

Measurement of the diffusion coefficient (D) of butylated hydroxyanisole (BHA) in low density polyethylene at 31°C was made by two techniques. (1) Measurement of diffusion rate in the absence of solvent was made by use of a film stack with BHA-loaded discs on top and bottom. After a given diffusion time, the films were separated and the BHA extracted from the films into 1 -propanol. The fluorescence of the solutions provided values of BHA concentration as a function of film position in the stack, from which the value 3.4 (SD 0.3) × 10^?9 cm² s^?1 for D was calculated. (2) Fluorescence monitoring, under oxygen free conditions, was used to measure rate of BHA extraction from a film into 1 -propanol at 31°C, and gave the value 3.8 × 10^?9 cm² s^?1 for D which agrees well with the value determined by measurement in the absence of solvent.