Polymer fibers, drawn

Although they have an endless variety of properties, polymers can be divided into three general categories, based on their form and resistance to stretching. These are plastics, fibers, and elastomers. Plastics differ in form from fibers whereas plastics exist as blocks or sheets, fibers have been drawn into long threads. Unlike plastics or fibers, elastomers can be stretched without breaking. Polyethylene packaging films and polyvinylchloride (PVC) pipe are examples of plastics. Orion carpets are made from polymer fibers, and mbber bands are elastomers. Some polymers, such as Nylon, can be formed into both plastics and fibers. 

Figure 11.14 Effect of applied strain on the 002 d-spacing of a PTT fiber drawn at 3.3 x measured by WAXD [76], Reprinted from Polymer, 42, Wu, J., Schultz, J. M., Samon, K. M., Pangelinan, A. B. and Chuah, H. H., In situ study of structure development in poly(trimethylene terephthalate) fibers during stretching by simultaneous synchrotron small- and wide-angle X-ray scattering, 7141-7151, Copyright (2001), with permission from Elsevier Science...

Figure 5. Polymer L X-ray diffraction pattern obtained from fibers drawn from the melt and cooled in air. Wide-angle pattern.

FIGURE 17.18 X-ray PF8 polymer fiber diffraction patterns, reported by Grell et al. (fiber c-axis vertical) after the following processes (a) fiber drawn from liquid crystalline melt (b) same fiber as (a), after thermalcrystallization (140 C for 1 h) (c) fiber exposed to saturated toluene vapor (40 C for 3 d) (d) same fiber as (c) after subsequent annealing (135 C for 1 h). (Reprinted from Grell, M., Bradley, D.D.C., Ungar, G., Hill, J., and Whitehead, K.S.,... 

A fringed-micellar structure was proposed in 1930 for the sttuctures of colloids and gels [19]. By adding the possibility of chain-folded crystals, as illustrated in the center of Fig. 5.42, all three limiting macroconformations are combined. Semicrystalline polymers, thus, are a system consisting of folded-chain crystals, intercrystalline amorphous, and possibly extended-chain subsystems (see Fig. 2.80). The latter are expected particularly in fibers drawn to large extension. Most samples have a macroconformation somewhere within the triangle of Fig. 5.42. 

Polymer fibers have a broad range of applications from carpets to ballistic protection. Fibers are typically fabricated through extrusion, with common process variations designated as wet spinning, dry spinning, melt spinning, and gel spinning. After extrusion, the fibers can be drawn in an intermediate or solidified state to achieve the desired final diameter and crystalhnity. 

Uniaxial iyii-ne- ak-se-9l (ca. 1828) adj. Of one primary axis and refractive index such as a drawn polymer fiber (e.g., drawn polyamide). 

Donald et al. [2] reported banded structures formed by several thermotropic polymers oriented by shear at temperatures above their softening points. Similar structures were also noted in fibers drawn from polymers with rigid backbones above the softening points. Viney et al. [3] point out that the banded structures observed in shear are due to the variation in the direction of the long molecular axis with respect to the direction of shear. Evidence obtained by both optical microscopy and electron diffraction measurements supports this view. Donald and Windle [4] studied the banded structure by electron microscopy and commented that The near sinusoidal variation in the direction of the principal axis of the refractive index ellipsoid is indeed reflecting the variations in the molecular orientation. Their transmission electron microscopy indicates that the transition from... 

Fig. 5.32. The hierarchical morphology exhibited by fibers [11], In the case in which rigid, rectilinear polymers are drawn from mesophases, an extended-chain crystal habit is adopted, with the chains ranning parallel to the fiber axis (left inset). In conventional flexible polymers, the semicrystalline folded-chain crystal habit exists (right inset).

---