ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
A numerical method has been developed that takes the streamline finite difference method for modeling fully developed multilayer polymer flows and adds to it a simple means of accounting for nonisothermal conditions. In industrial practice, temperature control is often used to match material viscosities and, thereby, to avoid flow instabilities. By numerically calculating both viscosity ratios and normal stress difference ratios, the numerical method allows one to judge the relative stability of different flows and to choose an intelligent set of experiments when designing a coextrusion process. The algorithm has been successfully tested for a number of polymer melt constitutive equations in flows where the viscosity jumps no more than two orders of magnitude between fluids. Results for a rheologically well characterized polystyrene low-density polyethylene system and for an industrially interesting high-density polyethylene/Ultem system show that the common practice of matching zero-shear viscosities is overly simplistic when interface shear rate, conduction, normal stress, and flow rate effects are taken into account.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760300705
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