Rheological observation of gelation and fusion process of poly(vinyl chloride) plastisol

This paper begins with a brief description of the history of development of PVC plastisol. It, then, presents technical background on the nature of PVC plastisol, covering subjects of particle size distribution and nature of agglomerates, viscosity aging and deagglomeration, rheology of suspension, gelation and fusion, and thermodynamic interaction between polymer and plasticizer. The main part of the paper concerns rheological observation of the gelation and fusion process of PVC plastisol, as the title of the paper indicates. This is a summary of recent work by the authors plus their new work on the effect of plasticizer type. The first half is the investigation of gelation and fusion mechanisms with use of a model plastisol system. Viscoelastic measurements, thermal analyses on the behavior of glass transition, and the scanning electron microscopic examination of the particulate structure were used to support the investigation. The last half considers the effect of the material variables on the gelation and fusion behavior; molecular weight, extractable additives (emulsifiers), agglomerates and fine particles, size of primary particles and plasticizer type are covered. Among these material variables, the plasticizer type has by far the largest influence on the gelation behavior. The observed solvent power is not necessarily in agreement with the thermodynamic interaction parameters found in the literature. It is indicated that a further systematic investigation is necessary to elucidate the nature of the plasticizer–polymer interaction.