Preparation and characterization of fibres from a thermotropic liquid crystal polyester with non-coplanar biphenylene units |
| |
| Authors: | Farshad Motamedi Ulrich Jonas Andreas Greiner Hans-Werner Schmidt |
| |
| Institution: | 1. Materials Department, College of Engineering , University of California , Santa Barbara , California , 93106 , U.S.A.;2. Materials Department, College of Engineering , University of California , Santa Barbara , California , 93106 , U.S.A.;3. Fachbereich Chemie , Johannes Gutenberg-University , 6500 , Mainz , Germany;4. Fachbereich Physikalische Chemie-Polymere, Phillipps-University Marburg , Hans Meerwein Stra?e Geb H, 3550 , Marburg , Germany |
| |
| Abstract: | Abstract Fibres were prepared from the nematic melt of poly(2,2′-dimethyl-4,4′-biphenylene phenylterephthalate). The phenyl substitution in the terephthalic acid moiety in combination with the non-coplanar biphenyl moiety prevent crystallization of this thermotropic polyester. Oriented fibres were prepared by two different methods. Similarly to other thermotropic liquid crystal polymer fibres, chain orientation can be achieved by an elongational flow in a down draw process. This polyester also allows tensile deformation of the spun fibres around the glass transition temperature. In both routes similar degrees of orientation and mechanical properties were obtained. Tensile moduli in the order of 40–45 GPa and tensile strengths up to 550–650 MPa were obtained. The orientation function values were determined to be in the order of 0·8–0·9. A comparison with other unsubstituted thermotropic liquid crystal polyesters at the same level of orientation revealed that the moduli are the same, although the substituents increase the chain diameter. This result may be attributed to an increase of the apparent shear modulus due to an interlocking mechanism of the rigid lateral substituents. |
| |
| Keywords: | |
|
|
