PHOTON-MIGRATION MEASUREMENT OF LATEX SIZE DISTRIBUTION IN CONCENTRATED SUSPENSIONS

Frequency-domain measurements of photon migration were conducted in co ncentrated polystyrene suspensions to assess their use for on-line par ticle sizing in undiluted process streams. Using a numerical inverse a lgorithm, particle-size distributions (PSD) and volume fractions of th ree latex suspensions with differing distributions were recovered from phase-shift measurements at 15 or less visible wavelengths. Compariso n to dynamic light-scattering measurements show excellent agreement. S ince it is the propagation characteristics of multiply scattered light instead of the amount of light detected that is employed to solve the inverse problem, the measurement technique provides a self-calibratin g (and therefore especially suitable) method for on-line process monit oring of PSD in the chemical-based industries.