Melt Rheology of Blends of Semi-Crystalline Polymers; Part II, Dynamic Properties of Poly(Ethylene Terephtalate) — Poly(Amide — 6,6) Molten Blends

  • L. A. Utracki
  • G. L. Bata
Part of the Polymer Science and Technology book series (PST, volume 20)


Melt rheology of poly(ethylene terephthalate) , PET, poly(amide -6,6), PA, and their blends were investigated at 240, 260, 280 and 300°C on Rheometrics Mechanical Spectrometer in a dynamic mode within the frequency range from 10-1 to 102 (rads/sec). Dynamic viscosity, storage and loss shear moduli were recorded.

First, the isothermal rate of the overall thermal degradation process for each sample was determined, from which the activation energy of the process, ED, as a function of the composition was computed. The determined values of ED)( - + 2) = 30 and 47 (kcal/mole) for PET and PA respectively are in agreement with the literature values. The rates of degradation as well as ED’s of the blends were found to be larger than those calculated from the properties of PET and PA by using an additivity rule.

Next, substracting the degradation effect from the recorded rheological signals, the true flow curves result. The dynamic viscosity, η*, and the dynamic measure of the primary normal stress difference coefficient, ψ*, as functions of the frequency, œ , were computed for each temperature, T, and composition, c. It was found that at T ≥ 260°C the addition of small amounts (c ≤ 10 wt%) of PA lowers the viscosity in full range of co . This effect was not observed at 240°C, i.e. for supercooled blends . Similar behaviour is observed for ψ ; here, however, the minimum occurs at a lower concentration, c ≃ 5%. As in the case of η*, the depression of ψ* due to PA presence is strongest at the highest temperature, 300°C, where ψ* is about ten-fold lower than that for PET. Regarding the structure of the blends, it has been observed that molten sample containing 5% PA was transparent, and that containing c > 10%, milky. The ATR-FTIR data shows that at least up to 30% PA, the continuous phase is made up of PET.


Polymer Blend Neat Polymer Thermal Degradation Process Molten Sample Phenylene Oxide 
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Copyright information

© Plenum Press, New York 1983

Authors and Affiliations

  • L. A. Utracki
    • 1
  • G. L. Bata
    • 1
  1. 1.Industrial Materials Research InstituteNational Research Council of CanadaMontrealCanada

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