Optical properties of extended-chain polymers under stress

Rafael G. Ramirez; Richard K. Eby

doi:10.1117/12.218192

1 September 1995 Optical properties of extended-chain polymers under stress

Rafael G. Ramirez, Richard K. Eby

Proceedings Volume 2554, Growth and Characterization of Materials for Infrared Detectors II; (1995) https://doi.org/10.1117/12.218192
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

Abstract

Birefringence and x-ray diffraction experiments have been carried out on Kevlar 49^R fibers under tensile stress to monitor structure changes under the stress field. The origin of the observed birefringence is discussed in some detail. Results from theoretical calculations using semi-empirical molecular orbital techniques are presented and contrasted to the experimental observations. The calculations involved the estimation of chain polarizability and were performed under simulated stress conditions using the AM1 Hamiltonian in MOPAC. Polarizability is then used to calculate the birefringence as a function of tensile stress, by using existing internal field theory. This theoretical approach is applied to predict the optical properties of highly oriented extended-chain polyethylene, as well as those for poly(p' phenylene therephtalamide); the latter being the base polymer in Kevlar fibers. Results reveal reasonable birefringence predictions when compared to available experimental results in the literature. Also, it is found that the contribution from orienting crystallites under the stress field, to the measured birefringence in Kevlar fibers, is only a small fraction of the total. However, the calculations predict a significant contribution from deformation (extension) at the molecular level.

Citation Download Citation

Rafael G. Ramirez and Richard K. Eby "Optical properties of extended-chain polymers under stress", Proc. SPIE 2554, Growth and Characterization of Materials for Infrared Detectors II, (1 September 1995); https://doi.org/10.1117/12.218192

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