Mixing, degassing, storage
Plastisols are almost always stored before processing. The plasticizer tends to swell the resin and the viscosity increases the more so as the temperature rises.
A more active plasticizer causes a higher viscosity.
Rheology
For a defined resin and extender, rheology is affected by the plasticizer type and level, fillers, and parameters independent of the formulation such as temperature, mixing procedure, storage time and conditions.
Apart all these elements, the viscosity is affected by the shear rate and the strain amplitude.
According to the resin and recipe, plastisols can have very different rheology behaviours:
* Practically Newtonian rheology over the entire shear range.
* Slightly pseudoplastic rheology.
* Dilatant behaviour
At room temperature, plastisols are liquid, but as the plastisol is heated, fusion and gelation take place, and the material is converted into a tough, homogeneous mass with a wide range of physical properties.
PVC pastes make-up 4-9% of the total PVC market.