Abstract
AbstractA rheological study has been performed to characterize the low molecular weight butyl polymers using a couette coni‐cylindrical viscometer. The bulk viscosity was determined as a function of temperature, weight‐average molecular weight, viscosity‐average molecular weight, and shear rate. The temperature dependence of the viscosity, while adequately represented by the Williams, Landel, and Ferry equation, is best described by an Arrhenius equation for the temperature range investigated. The viscosity is shown to vary with the 3.5th power of the weight‐average molecular weight above a critical molecular weight and to the 1st power below this molecular weight. Although the ratio of the weight‐average molecular weight to the number‐average molecular weight usually affects the flow properties of polymers, this was not true for the polymers investigated. The bulk viscosity was found to be independent of the molecular weight distribution for the temperature and shear rate range studied. It has been shown that a definite relationship exists between the bulk viscosity and the viscosity‐average molecular weight as determined by dilute solution viscosity. A mathematical model has been developed to relate these two parameters as a function of temperature and shear rate.
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