Melt Rheology of Blends of Semi-Crystalline Polymers; Part II, Dynamic Properties of Poly(Ethylene Terephtalate) — Poly(Amide — 6,6) Molten Blends
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.
KeywordsPolymer Blend Neat Polymer Thermal Degradation Process Molten Sample Phenylene Oxide
Unable to display preview. Download preview PDF.
- 1.Anonym., Polymer News, 7 (2): 86 (1981).Google Scholar
- 6.L. A. Utracki and M. R. Kamal, “Melt Rheology of Polymer Blends”, Paper presented at IMRI mini-symposium series “Polymer Blends -1981” Montréal, Quebec. To be published in Polymer Eng. Sci.Google Scholar
- 7.L. A. Utracki and G. L. Bata, “Polymer Alloys”, CAN-PLAST 1981, Montréal, November 1981.Google Scholar
- 8.O. Olabisi, “Polyblends” prepared for Kirk-Othmer Encyclopedia of Chemical Technology, April 1982.Google Scholar
- 8a.See also: O. Olabisi, L. M. Robeson and M. T. Shaw, “Polymer-Polymer Miscibility”, Academic Press, New York, 1979.Google Scholar
- 9.R. Simha, Paper presented at the 1st IMRI Mini-symposium on Phase Equilibria in Polymeric Systems, Montréal, 1980, NRCC spec. ed. 1981. To be published in Polymer Eng. Sci.Google Scholar
- 12.L. A. Utracki, M. R. Kamal, V. Tan, A. M. Catani and G. L. Bata, J. Appl. Polymer Sci., to be published.Google Scholar
- A. Garton, private communication.Google Scholar
- 17.C. Macosko and J. M. Starita, SPE J., 27: 38 (1971)Google Scholar
- J. -J. Hechler, private communication.Google Scholar
- 19.J. D. Ferry, “Vicoelastic Properties of Polymers”, J. Wiley & sons, New York, 2nd edition, 1970, Chs. 9 and 10.Google Scholar