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Surface Tensions of Molten Polymers as a Function of Molecular Weight and Temperature.

Published online by Cambridge University Press:  25 February 2011

Bryan B. Sauer
Affiliation:
DuPont, Central Research and Development, Wilmington, DE 19880-0356
Gregory T. Dee
Affiliation:
DuPont, Central Research and Development, Wilmington, DE 19880-0356
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Abstract

Surface tensions of viscous molten polymers were measured with the modified Wilhelmy method. Small diameter fibers were used as vertical surface tension probes giving rise to rapid equilibration of the wetting meniscus. Noise due to thermal convection currents was suppressed by the use of a baffle tube to protect the electro-balance which allowed us to extend our studies to temperatures exceeding 400°C. The precision of the surface tension measurement at T<350°C for n≤10,000 Poise is better than 0.5%. Discussion is made of the rate of meniscus equilibration as a function fiber diameter. The surface tensions of polystyrene(PS), polydimethylsiloxane(PDMS), poly(ethylene glycol)(PEG), poly(propylene glycol)(PPG), and polyethylene(PE) were determined as a function of MW and temperature in order to compare with theoretical predictions. The Cahn-Hilliard interfacial gradient theory is used in conjunction with equation of state models using pressure-volume-temperature data as the input. Good agreement with experiment is found using one adjustable parameter which is independent of MW, for both polar and non-polar polymers.

Type
Research Article
Copyright
Copyright © Materials Research Society 1992

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