Plasticizers Distributive mixing

The first step in processing is usually powder mixing in a high speed, intensive mixer. PVC resin, stabilizers, plasticizers, lubricants, processing aids, fillers, and pigments are added to the powder blend for distributive mixing. 

The action of mixing plastic compound can be distributive and/or dispersive. They are not physically separated. In dispersive mixing, there will always be distributive mixing. However, the reverse is not always true. In distributive mixing, there can be dispersive mixing only if there is a component exhibiting a yield stress and if the stresses acting on this component exceed the yield stress. 

Finally, the mixing process has a pronounced effect on plasticizer distribution and thus on the properties of plasticized mateiials. " " Preblending or multistage processes were developed to increase the homogeneity of plasticized materials. Improved mixing affects not only physical distribution of the plasticizer but also facilitates its interaction with the matrix polymer. This can be seen from the improved retention of plasticizer after extraction with various solvents. ... 

DiStribUtiVG Mixing. The extent of distributive mixing can be determined from the total shear deformation of the plastic melt in the melt conveying zone. The total shear deformation is also called the total shear strain-, it is determined by the product of the shear rate and the length of time that the fluid is exposed to the shear rate. For instance, if the plastic melt is exposed to a shear rate of 100 s for 15 s, the resulting shear strain is 100 x 15 = 1500. The units of shear strain are dimensionless. The shear rate is determined by the velocity profiles in the extruder. 

Ghebremeskel A, Vemavarapu C et al (2007) Use of surfactants as plasticizers in preparing solid dispersions of poorly soluble API selection of polymer-surfactant combinations using solubility parameters and testing the processability. Int J Pharm 328(2) 119-129 Gogos C, Liu H (2012) Laminar dispersive and distributive mixing with dissolution and applications to hot-melt extrusion. In Douroumis D (ed) Hot-melt extrusion pharmaceutical applications. Wiley, New York, pp 261-284... 

Figure 2.17 Erwin s experiments using Couette flow with repeated orientations. Reproduced with permission from G.M. Gale, Distributive Mixing in Plastics Extrusion, Rapra Technology Members Report No.46, Rapra Technology, Shrewsbury, UK, 1980, Figure . 1980, Rapra Technology)...

---