Polybutadiene latex particle size distribution analysis utilizing a disk centrifuge

Polybutadiene (I) latexes prepd. by emulsifier-free emulsion polymn. and having particle diam. 50-300 nm for both unimodal and bimodal particles size distributions were analyzed by the line-start (LIST) method in a Brookhaven disk centrifuge photosedimentometer. A special spin fluid was designed to be able to sediment I since the d. of the polymer is 0.89 g/cm3 and is thus less dense than its suspending medium. D. and viscosity gradients were created simply by adding 5 different mixts. of EtOH, water, and emulsifier in d. sequence to the spinning disk. Coagulation problems caused by dilg. I latexes with EtOH were overcome by using the nonionic surfactant Triton X-100. Good agreement in the av. particle size and distribution as well as polydispersity was obtained between transmission electron microscopy and disk centrifuge data. The anal. time for I latex particle sizing thus was reduced from several days to approx. 1 h