SynopsisPlastisols of poly(viny1 chloride) (PVC) are suspensions of fine resin particles in plasticizer with about a 50% resin volume fraction. Typically, the gross particle size ranges from about 15 to 0.2 Frn and smaller, where the common practice of spray drying these resins dictates that the size ranges include agglomerates as well as the ultimate particles. In this work we have related the particle size distribution to the dynamic mechanical behavior with model plastisols prepared from various particle-size fractions of a commercial resin. This relationship, together with the microscopic observation of the particle dispersions, provided an interpretation of the plausible mechanisms of the viscoelastic response. The morphological observation of the particle aggregates, the changes Of the particle size distribution during the aging, and the above viscoelastic study have established that deagglomeration is the dominant cause of the increase of viscosity during aging.

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Data on the solubility and diffusion of vinyl chloride monomer (VCM) in PVC resin powders have been combined with published solutions of Fick's diffusion equation to yield predictions of the amount and rate of loss of residual VCM (RVCM) from rigid PVC pipe under storage and service conditions. The principal factors controlling VCM migration are the initial VCM content, thickness of the PVC section, temperature, and the age of the PVC product. Analytic solutions are presented for RVCM loss from freshly extruded pipe (uniform VCM concentration) into either the storage environment or the pipe contents. From these solutions, estimates are made for the real-world situation of closed-system service following variable storage periods. The validity of this approach for rigid PVC pipe in water-service is supported by reasonable agreement between its predictions and experimental laboratory data on the VCM content of water stored in PVC pipes. Both the predictive model and experimental data indicate that PVC pipe containing 5 1 mgikg (1 part per million) residual VCM will result in VCM concentrations in water of less than 0.002 mgikg under any expected service conditions.

A detailed study was made of the thermal behavior of poly(vinyl chloride) (PVC) homopolymers, whose chain length and structure were independently manipulated. Normal PVC polymerizations are made at temperatures, the selection of which determines the polymer chain length. In the case of PVC, this choice of temperature also determines its syndiotacticity, and so, its glass transition temperature, and in many ways, its processibility. The ability to understand how to control chain structure and length in PVC is critical in designing polymers for selected specific end use conditions. The thermal spectrum is known to be one measure of how polymers will perform. This study reveals how such controlled chain length/structure PVCs are characterized by thermal methods, and how one can separate individually the effects of syndiotacticity and molecular weight on thermal properties of poly(vinyl chloride).

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