Optothermal properties of fibers. I. Relations between optical properties and change of the density and mechanical loss factor for annealed polyester fibers

Abstract

SYNOPSISPolyester (Egyptain manufacturers) fibers were annealed in the temperature range 80-190°C for time intervals from 1 to 10 h. The density of the annealed fibers was measured by a system based on the theory of vibrating strings. The fiber diameter was also determined, using the laser forward diffraction technique. Refractive indices and birefringence for annealed fibers at different temperatures and constant time, 1 h, were measured by the polarizing interference microscope. The behavior of fiber density and the mechanical loss factor at different annealing temperatures and times were discussed at different optical parameters. The results obtained clarify the effect of annealing time and temperatures on the optical, density, and mechanical loss factor behavior of polyester fibers. Microinterferograms are given for illustration. 0 1995 John Wiley & Sons, Inc. I NTRO DUCT10 NBirefringence is a measure of the total molecular orientation of a system; it is an excellent property to use for the study of orientation in polycrystalline polymer. The birefringence measurement is thus a rapid and powerful tool for the study of morphological characteristics of deformed polycrystalline polymers. Since birefringence is a measure of the total molecular orientation of the two-phase system, its examination in conjunction with other physical measurements (X-ray, density, mechanical loss factor, etc.) yields considerable insight into the characteristics of the bulk polymer.' One of the important parameters characterizing the crystalline structure of polymers is the degree of crystallinity. The relationship between the degree of crystallinity and the density of the polymer has great influence on the viscoelastic properties of crystalline polymers.' Also, it is known that annealing at different conditions leads to a change in the density and loss tangent, etc.2Long bundles of poly(ethy1ene terephthalate) (PET, manufactured in Egypt) make up a crystalline ~~ * To whom correspondence should be addressed.Journal of Applied Polymer Science, Vol. 56, 1355Vol. 56, -1366Vol. 56, (1995 0 1995 John Wiley & Sons, Inc.CCC 0021-8995/95/101355-12 polymer that is among the most convenient ones to s t~d y .~ It can be prepared in both the amorphous and the crystallized states within a broad range of values of the degree of cry~tallinity.~ The dynamic mechanical loss modulus is a measure of the energy dissipated by the polymer as a consequence of molecular relaxation processes in the noncrystalline region of the polymer. ' In this work, the density of polyester fibers, with different annealing conditions, was measured to estimate the variation due to the annealing process and, on the other hand, to describe how these variations may lead to understanding of the molecular structure response to the applied annealing process. An interferometric method and a resonance technique are used to determine the optical parameters, density, and mechanical loss factor. The relations among the density, mechanical loss factor, and optical parameters we...

The Activation Energy and Some Structural Parameters of Thermally Treated Polypropylene Suture Fibers

“…The experimental values of the refractive indices and polarizabilities were used to calculate the polarizability of the monomer unit at different temperatures by suitable equations given elsewhere [2,8,9].…”

“…These optical properties provide parameters that characterize the structure of the polymer on the molecular level. It is well known that birefringence is one of the most sensitive indicators of the anisotropy in polymers fibers; i.e., the degree of macromolecular orientation [3][4][5][6][7][8][9][10]. So, oriented polymers exhibit important changes on heating and produce thermal stress which may be an interesting method of characterizing fibers.…”

Optothermal properties of fibers?20?relation between physical structure and mechanical properties of cold drawn polypropylene fibers

“…The totally duplicated image of the fiber obtained with Pluta polarizing interference microscope, discussed in detail elsewhere,15–17 was used to calculate the mean refractive indices n a ‖ and n a ⟂ of PP fibers.…”

“…The mean values of the refractive indices of the fiber and the total mean birefringence were calculated from the totally duplicated and nonduplicated images of the fiber using Pluta interference microscope 17–19…”

Optothermal properties of fibers. X. Temperature dependence of the skin?core structure of nylon-6 fibers

“…[3][4][5][6][7][8][9] The The study of optical anisotropy in polymer fibers most available technique for changing the polyplays an important role in the knowledge of the meric structure is the annealing and quenching molecular arrangement within these fibers.…”