Hydrocysts

Figure 4.23. Different possible flow modes in rotary processing of polyester resin 1 - quasi-solid rotation 2 - stable hydrocyst 3 - rotation in an annular (ring-shaped) layer, 4 - cascade flow. [Adapted, by permission, from I. L. Throne, I. Gianchandani, Potym. Eng. Sci., 20 (1980), 913.]...

Figure 10.25. Hydrocysts and bad distributions in a PVC plastisol processed by rotational molding.

The rates of gelation and fusion processes of PVC plastisols are more critical in the operations involving simultaneous heating and flow of plastisol, such as present in rotational molding. It is because inappropriate plastisol viscosity (dilatant or too viscous plastisol) and a fast gelation process may alter required distributions of material, formation of bubbles and hydrocysts ° (see for example Figure 10.25). 

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