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Viscoelastic properties of a 60 mol% para‐hydroxybenzoic acid/40 mol% poly(ethylene terephthalate) liquid crystalline copolyester. I: Effect of temperature history
Author(s) -
Hayase S.,
Driscoll P.,
Masuda T.
Publication year - 1993
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.760330209
Subject(s) - copolyester , viscoelasticity , materials science , rheology , polymer , ethylene , hysteresis , polymer chemistry , glass transition , hydroxybenzoic acid , chemical engineering , composite material , organic chemistry , polyester , chemistry , catalysis , physics , quantum mechanics , engineering
In this paper, the rheology of a 60 mol% para‐hydroxybenzoic acid (PHB)/40 mol% poly(ethylene terephthalate) (PET) copolyester (herein referred to as PHB60/PET40) produced by Unitika Co., Japan, was investigated using viscoelastic property temperature sweeps. In addition to the large‐scale hysteresis (super‐cooling) of viscoelastic properties that has also been seen with other PHB‐based materials, in which it is possible for several PHB linkages to occur side by side along the polymer backbone (most notably the PHB60/PET40 polymer produced by Tennessee Eastman), smaller‐scale viscoelastic transitions, one present in heating, and believed to be associated with the partial isotropization of liquid crystalline material, and the other apparent on cooling, occurring at a lower temperature than the first and thought to be associated with the opposite process, were observed. When overall mol% PHB composition along individual chains is considered, the well‐defined appearance of the additional smaller‐scale rheological transitions seen here is believed to be due to a unimodal composition distribution, rather than a bimodal distribution of which there is increasing evidence in the Tennessee Eastman materials. This difference is believed to be caused by differences in the preparation technique used for the Unitika version of the polymer.