Institutional Repository
Technical University of Crete
Technical University of Crete
EN
|
EL
| URI: | http://purl.tuc.gr/dl/dias/64576DAC-DCFA-4C28-8E1F-452EE631426A | ||
| Year | 1986 | ||
| Type of Item | Peer-Reviewed Journal Publication | ||
| License |
|
||
| Bibliographic Citation | A. D. Gotsis and D. G. Baird, "Primary normal-stress difference for two liquid crystalline copolyesters", Rheolog. Acta, vol. 25, no. 3, pp. 275-286, May 1986. doi:10.1007/BF01357954 https://doi.org/10.1007/BF01357954 | ||
| Appears in Collections |
The primary normal-stress difference,N 1, was determined in both steady and transient shear flow experiments for thermotropic copolyesters of 60 and 80 mole% p-hydroxybenzoic acid (PHB) and polyethylene terephthalate (PET).N 1 was observed to be negative for the 80 mole% system at low shear rates and temperatures below 332 °C (a tensile stress, e.g. σ11 is taken here to be positive). At higher shear rates and for temperatures above 332 °C,N 1 was found to be positive. Values ofN 1 for the 60 mole% pHBA/PET system were always positive over the same range of shear rates. Although it is not certain as to the origin of the negative values, a probable cause is small density changes upon the inception of flow as well as the existence of a solid phase or some texture development in the melt. However, it is shown that it is thermodynamically admissible for liquid crystalline fluids to exhibit negative values ofN 1.
Copyright © DIAS 2013
