Homogeneous Nucleation from Polymer Solutions

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Authors: John H. Jennings
Page Range: 311-319
Published in: Polymers Research Journal, Volume 8 Issue 4 (2014)
ISSN: 1935-2530

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There have been various attempts since the two papers by (Han and Han) to predict the rise in superheat due to addition of polystyrene in solvents including toluene, benzene and cyclohexane. Calculation of the nucleation rate is a cumbersome way to attack the problem. The papers other than (Jennings) focus on getting a value for the nucleation rate J. In Jennings’ formulation a simple vector calculus argument eliminates the need to calculate J. Each curve for (Jennings and Middleman) data is more or less a line and the object is to calculate the slope of the lines in the (w2, T) plane where w2 is the weight fraction polystyrene in cyclohexane and T is temperature Kelvin. All lines meet at the point (0,Tl) where J is equal for all 4 molecular weights and Tl is the limit of superheat of pure cyclohexane at 1 atm. This paper shows how Jennings’ approach is simple and gives a beautiful effective equation. In expanded form I am proposing a new equation for the limit of superheat T, by extending the limiting equation published by (Jennings) because the data are lines. Because they are lines the limiting slope would be the true slope. The additional temperature rise in the superheat limit is inversely proportional to MW polymer and directly proportional to weight fraction polymer in the solution. It is a semi-empirical argument. One would believe that experiments with polystyrene in cyclopentane, n-hexane and n-heptane would give the same lines in the data as cyclohexane in the experimental setup used by (Jennings and Middleman).

Keywords: processing technologies, thermal properties, polymer solution, nucleation