Powders, nonporous plastic

In order to use this unit also for catalyst particles of any shape, the standard method was modified (method lie in Table 3) in the same way as described for the determination of the thermal conductivity of nonporous plastic powders in [13]. The concept is to compare the thermal conductivity of the catalyst pellet X with the conductivity of a binary liquid mixture. If the liquid mixture can be adjusted such that it has the same conductivity as the pellet, the conductivity of a fluid/solid system A (consisting of catalyst particles and the liquid mixture) will be independent of the solid content, and... 

If, on the other hand, a system is produced by a random conglomeration of a large number of individual elements (porous or nonporous), the result will be an addition system. They also include both natural and man-made materials sand, gravel, woven fabrics, powders, fibrous materials, paper. Addition systems also include a special type of gas-filled plastics, the so-called syntactic foams. 

There are two types of suspension polymerization. Beads are nonporous polymer particles that are formed where the polymer is soluble in monomer such as PS and PMMA. Powders are porous particles where the polymer is insoluble in monomer and precipitates during polymerization. The polymer powders are composed of many small primary particles. The powder particles are opaque and have substantial internal porosities. Control of particle porosity is very important for it controls absorption rate of plasticizers such as PVC. The production of PS beads and PVC powders by suspension polymerization will be described later as outstanding industrial examples. 

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