Processing highly filled polyvinyl chloride in double-screw mixers

Abstract

As there is a limit on the effect that plasticization can have on viscosity and because of the rate of destruction of the polymeric system the manufacture of highly filled PV compositions with optimum conditions of low shear stress, freedom from attack by oxygen on the polymer composition, and a continuous technological process is proposed to guarantee constant quality in the properties of tile and linoleum. Screw type mixers must be replaced by continuous type SN double-screw mixers. Several screw designs are tested and samples subjected to differential thermal analysis and thermogravimetric analysis. The rheological properties of pastes obtained from tile and linoleum specimens were tested to obtain comparative data on the structural formation processes. The tests indicate that polyvinyl chloride processed in a double screw machine has a higher molecular weight and a more highly branched molecule than the same composition processed in a rotary mixer. A study of PVC mixtures indicate that it is suitable to plasticize highly filled PVC compositions in a double screw type SN mixer.