Dependence of Gelation and Fusion Behavior of Poly(vinyl chloride) Plastisols upon Particle Size and Size Distribution

Abstract

Poly(vinyl chloride) (PVC) plastisol is a suspension of small particles of PVC resin in plasticizer. The processing of plastisol typically involves flow at room temperature during coating or mold filling, and gelation and fusion as the plastisol is heated to form the final product. This paper explores the effect of the particle size distribution on the gelation and fusion behavior. For this purpose a commercial PVC resin was air-classified into fractions of different particle size. Samples were then reconstituted to have known particle size distributions. Particular emphasis is placed on the effect of the fine particle fraction on the material behavior. The progress of gelation and fusion were followed by measurement of the viscoelastic properties as a function of treatment temperature using a mechanical spectrometer. Characteristic changes in the viscoelastic behavior were associated with changes in morphology, observed with a scanning electron microscope, enabling qualitative discrimination of the gelation and fusion processes. The larger fraction of fine particles gave higher values of G′ and G″. It seems that the fine particles promote the interparticulate bonding, when the particles start fusing together.