Improved plastisol flow and reduced level of plasticiser in paste poly(vinyl chloride) formulations

Adverse effects from the usage of plasticisers and diluents in the manufacture of flexible polyfvinyl chloride) (PVC) products have recently received increased environmental concern. As a consequence there is a lot of work in progress to find more environmentally friendly systems and/or systems that can reduce the consumption of organic liquids in the plastisol industry. Model systems of paste PVC resins have been prepared by blending a fine particle resin (0-2-2 (mu)m and a resin of 15(mu)m monodisperse PVC particles in different ratios. The effects of particle size and particle size distribution on particle packing and plastisol rheology were assessed in plastisols prepared from these resin blends. By optimising the blending ratio, it was possible to reduce plasticiser levels in the formulation from 50 to 30 phr and still have a satisfactory low viscosity and an almost Newtonian flow behaviour. Additional effects of the well defined and very fine particle size of the resins studied were freedom from sedimentation in the plastisols and the possibility of making very thin films. Satisfactory mechanical and physical properties for fused films and coated steel plates were maintained even at the lowest plasticiser level. Film tensile strengths were found to be reduced on increasing the relative amount of the large particle resin. However, this could be compensated for by the reduction of plasticiser level made possible by the more optimised packing. Fire, migration, and film hardness properties were all found to be improved on reducing the level of plasticiser in the formulations.