(78a) Larry Duda's Career Interest in Diffusion in Polymers Begins at Dow

Larry Duda hired into Dow in 1963. Larry and Marge were newly weds and proceeded to have 4 children in 3 1/2 years. Actually Larry and Jim Vrentas were hired at the same time, both had just received their Ph.D.'s for the University of Delaware. Larry worked for Art Metzner and Jim for Bob Pigford. Larry began working with Doug Leng in the area of membrane separations. This work focussed on using membranes to seek solutions for some of industry's toughest separation problems. Soon there was another challenge. Dow was making polystyrene using a large diameter stirred tube polymerizer. Apart from the mechanical problems this presented, it also let to poor temperature control and a broad residence time distribution. Larry Duda and Jim Vrentas were asked to consider the feasibility of a tubular polymerizer with no moving parts. The problem was would the shear stresses created by the flow be sufficient to keep the wall region clean? This in turn required diffusional information on polymer chains entering the main stream and monomer diffusing into the wall region. That led to the building of the McBain-Bakr balance and the interferometer wedge, an insitu method of determining local concentrations and how they changed over time. When Larry left Dow for Penn State, he was encouraged to take the elaborate McBain balance with him. The paper gives other examples of experiments and mathematical analyses.