Arthur K. Doolittle

Bio: Arthur K. Doolittle is an academic researcher. The author has contributed to research in topics: Viscosity & Newtonian fluid. The author has an hindex of 4, co-authored 5 publications receiving 1885 citations.

Studies in Newtonian Flow. II. The Dependence of the Viscosity of Liquids on Free‐Space

Abstract: In this paper it is shown that the viscosity of the liquid normal paraffins can be accurately defined as a simple function of relative free‐space except for values in the neighborhood of the freezing points of each compound A novel method of extrapolating the specific volumes of this family of compounds to absolute zero is described which permits the calculation of reliable values of the relative free‐space from density dataAn expression of the same form as the author's function, but in which temperature rather than free‐space is the primary variable (the so‐called Andrade equation), fails to reproduce the viscosity of n‐heptadecane over the same range of temperatures within the limits of the known accuracy of the measurements

Studies in Newtonian Flow. I. The Dependence of the Viscosity of Liquids on Temperature

Abstract: It is shown that the Walther and Andrade equations, while very satisfactory for moderate ranges of temperature, are not adequate to define the dependence of the viscosity of liquid normal paraffins on temperature over extended ranges. One method of developing a viscosity‐temperature relationship is presented that gives equations defining this dependence with satisfactory validity. The purpose of this paper is to show that the precise dependence of the viscosity of liquids on temperature is complicated. This is in contrast to the relatively simple relation for the precise dependence of the viscosity of liquids on free‐space which will be presented in subsequent papers.

Studies in Newtonian Flow. III. The Dependence of the Viscosity of Liquids on Molecular Weight and Free Space (in Homologous Series)

Abstract: The free‐space concept, previously applied to variation resulting from a change in temperature only, is here adapted to a case where both temperature and molecular weight vary. The molecular weight range of the n‐paraffins illustrative of this case is limited to m=100 through m=240. Over this range of molecular weights the family of lines represented by lnη=B(ν0/νf)+lnA intersects the vertical axis at very nearly a common point. By assuming a common intercept and representing the slopes of this family of lines in terms of molecular weight, an expression defining viscosity as a function of molecular weight and free space is deduced. This expression reproduces the ``selected data'' satisfactorily over the molecular weight range mentioned. Its greater significance as a step in the development of a far more useful function will become apparent in the succeeding paper.

Studies in Newtonian Flow. IV. Viscosity vs Molecular Weight in Liquids; Viscosity vs Concentration in Polymer Solutions

Abstract: This is the final installment in the current series entitled ``Studies in Newtonian Flow.'' In this paper, the molecular weight—free‐space function applicable to n‐paraffins m=100 through m=240 at various temperatures is further generalized to apply to homologous series of all Newtonian liquids at constant temperature. The resulting molecular weight function thereby loses some fidelity, and the slopes and intercepts no longer have physical significance. The generalized logarithmic decrement equation nevertheless reproduces viscosity data over extended ranges of molecular weight (at constant temperature) far better than expressions previously proposed. The equation is extended to apply to mixtures of liquids and finally to polymer solutions.

Molecular Transport in Liquids and Glasses

Abstract: We have derived, by using simple considerations, a relation between the diffusion constant D in a liquid of hard spheres and the ``free volume'' vf. This derivation is based on the concept that statistical redistribution of the free volume occasionally opens up voids large enough for diffusive displacement. The relation is D=A exp[−γv*/vf], where v* is the minimum required volume of the void and A and γ are constants. This equation is of the same form as Doolittle's [J. Appl. Phys. 22, 1471 (1951)] empirical relation between the fluidity φ of simple hydrocarbons and their free volume. It has been shown [Williams, Landel, and Ferry, J. Am. Chem. Soc. 77, 3701 (1955)] that the Doolittle equation also can be adapted to describe the abrupt decrease in molecular kinetic constants with decreasing temperature that accompanies the glass transition in certain liquids. Our result predicts that even the simplest liquids would go through this glass transition if sufficiently undercooled and crystallization did not oc...

Mechanical properties of solid polymers

Abstract: A concise, self-contained introduction to solid polymers, the mechanics of their behavior and molecular and structural interpretations. This updated edition provides extended coverage of recent developments in rubber elasticity, relaxation transitions, non-linear viscoelastic behavior, anisotropic mechanical behavior, yield behavior of polymers, breaking phenomena, and other fields.

Studies in Newtonian Flow. II. The Dependence of the Viscosity of Liquids on Free‐Space

Abstract: In this paper it is shown that the viscosity of the liquid normal paraffins can be accurately defined as a simple function of relative free‐space except for values in the neighborhood of the freezing points of each compound A novel method of extrapolating the specific volumes of this family of compounds to absolute zero is described which permits the calculation of reliable values of the relative free‐space from density dataAn expression of the same form as the author's function, but in which temperature rather than free‐space is the primary variable (the so‐called Andrade equation), fails to reproduce the viscosity of n‐heptadecane over the same range of temperatures within the limits of the known accuracy of the measurements

Colloquium : The glass transition and elastic models of glass-forming liquids

Abstract: Basic characteristics of the liquid-glass transition are reviewed, emphasizing its universality and briefly summarizing the most popular phenomenological models. Discussion is focused on a number of alternative models which one way or the other connect the fast and slow degrees of freedom of viscous liquids. It is shown that all these ``elastic'' models are equivalent in the simplest approximation.