Particle sizing of flocculated latex particles by physisorption of nitrogen

Physisorption of N at 1 specific pressure is used to det. the sp. surface area of a flocculated polystyrene (I) latex by applying the Brunauer, Emmett and Teller (BET) theory. Assuming that a flocculated sample of polymer latex is composed of distinct spherical latex particles (i.e., there is no coagulation of particles), the vol.-surface-av. diam. can be calcd. The resulting diams. are compared to sizes obtained using a disk centrifuge sedimentometer, which fractionizes the particles by sedimentation. The diams. from both techniques were in good agreement, showing that physisorption of N, which is a simple technique, can be used to det. sizes of flocculated latex particles. This agreement also shows that flocculation of the I latex produced sep. nonporous spherical particles. When flocculation of a latex occurs above its glass transition temp., coagulation will occur. While other particle sizing techniques can produce particle size distributions, the physisorption of N only gives the vol.-surface-av. diam. However, 1 advantage of the physisorption of N is that it covers a broad range of particle sizes compared to most other technique