Volume 14, Issue 5, 01 May 1943
Index of content:
14(1943); http://dx.doi.org/10.1063/1.1714979View Description Hide Description
A series of flow and recovery tests are used as a basis for describing and interpreting the elastic,viscous, and tensile properties of a typical solid linear high polymer. Extensions of viscose rayon at 70°F and 65 percent R.H. are given under loads of 0.1 to 1.0 grams per denier (1900 to 19,000 lb. per sq. inch) for times up to 106 seconds. Recoveries at 70°F are given for times up to 106 seconds at 65 percent R.H. and also after wetting and reconditioning to remove internal strains. The data are interpreted in terms of changes in modulus, viscosity, restoring forces, viscousflow,crystallization, and internal load distribution.
14(1943); http://dx.doi.org/10.1063/1.1714980View Description Hide Description
Transient bearing temperature and friction data have been obtained for a journal bearing system operating under thick film conditions. The journal speed was varied from 1.5 to 11.0 r.p.s., and tests were made with five different lubricants. Equilibrium values of temperature and friction were determined by exponential extrapolation of data taken over time intervals of three to six hours. By inversion of the Petroff formula, average film temperatures were calculated from the friction data. These were in all cases greater than the directly measured bearing temperatures, although the excess was in general less than 10°F. The equilibrium temperature data for the various lubricants and speeds were correlated on the basis of heat balance considerations by the formula:,the film viscosity μ and temperatureT referring to equilibrium conditions, Ta denoting the ambient temperature, and N the journal speed. This relation permits the calculation of the equilibrium conditions for a journal bearing system of the type used here for any lubricant and journal speed. The asymptotic rate of approach to equilibrium was also quantitatively correlated to the final equilibrium conditions. For Gulflube 10 the equilibrium frictional force was found to increase monotonically with the journal speed, the rate of increase quickly tapering off for speeds greater than 4 r.p.s. Its value at 11 r.p.s. is only 0.14 of that to be expected if there were no fall in film viscosity. For Gulflube 30 the friction force curve rises to a maximum at 3 r.p.s. and then falls slowly for greater speeds. The value at 11 r.p.s. is here only 0.04 of that for a constant film viscosity system.
14(1943); http://dx.doi.org/10.1063/1.1714981View Description Hide Description
14(1943); http://dx.doi.org/10.1063/1.1714982View Description Hide Description
Staudinger's relation between η sp /c and the molecular weight of a chain molecule solute should theoretically apply only if the chain molecules are kinked in a purely random way. With actual solutions, one would expect the kinked chains to be more or less tightly coiled than for purely random kinking, depending on whether the average cohesive energy density between like units (solvent molecules and solute submolecules) is greater or less than that between unlike units. The tighter the coiling, the less is the specific viscosity, for a given solute molecule chain length. This cohesive energy density difference is closely related to μ1, the constant, characteristic of a given solute‐solvent system, which enters into the equations recently derived by the author for the activities of the components and for related quantities, such as osmotic pressures, solubilities, and precipitabilities. From this relationship, it has been shown that the η sp /c values for solutions of a given polymer in different solvents should, in general, be symbatic with the proportion of a poor solvent which is required to produce precipitation of a solid phase. Data from the literature on polystyrene and polybutene solutions are in agreement with this conclusion.