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Errors that result from thermal degradation during shear measurements on some molten polymers
Author(s) -
Gregory D. R.,
Wampler F. C.
Publication year - 1985
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760250609
Subject(s) - materials science , polymer , rheology , degradation (telecommunications) , polyester , shear (geology) , polymer degradation , composite material , shear rate , thermal , thermodynamics , telecommunications , physics , computer science
Shear sensitivities of molten polymers may be determined from measurements made on individual samples subjected in one test to a series of either increasing or decreasing shear rates. Many polymers, including polyesters, degrade when molten. If the effect of degradation is significant, and is ignored during data analysis, a significant error could result. The magnitude of the error depends directly on the magnitude of the reaction rate constant for degradation, which differs from polymer to polymer and which increases as temperature increases. In rheological characterization of molten polymers, one should know or determine the degradation behavior of the polymer being investigated and then account for it in the data analysis. Experimental results for poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) are presented and discussed. Ways to account for degradation in shear sensitivity measurements are also presented.