Effect of Hot-Stretching

The hot-stretching was performed at the temperature where the tensile storage modulus at 10 Hz was 10 MPa [212°C]. The stress-strain curve at a strain rate of 0.05 s is shown in Fig. 9.21. The curve is a typical one for a viscoelastic body in a rubbery region. 

The refractive indices at 588 nm along three principle axes for films with various draw ratios are illustrated in Fig. 9.22. In this experiment, the hot-stretching was performed in the x direction. 

As mentioned, the solution-cast film is randomly oriented in the film plane, i.e., = Uy, but the principle refractive index in the 

The wavelength dispersion of in-plane and out-of-plane birefringences for the stretched films is shown in Fig. 9.23. As seen 

The negative in-plane birefringence in CTA suggests that the direction of the polarizability anisotropy associated with the acetyl group is perpendicular to the main chain. This result corresponds to the previous reports [36,43, 44, 53]. 

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Figure 10. Effect of hot-stretching on subsequent room temperature Instron stress strain curves of one BPFC-DMS block polymer. 27% silicone of DPn = 36.

Source Reprinted with permission from Ozbek S, Isaac DH, Carbon fiber processing Effects of hot stretching on mechanical properties, Mater Manuf Process, 9(2), 179-197,1994. Copyright 1994, CRC Press, Boca Raton, Florida. 

KGS632). The weak band which appears as a shoulder ca. 20 cm 1 to low frequency of the main NH band in very dilute solutions and of roughly one-twentieth of its intensity has become a classical example of a hot band (64JCP(4l)3274) similar bands have been identified in substituted pyrroles. The position of the NH stretching vibration is sensitive to the number, type and position of ring substituents effects of substituents are additive and independent provided that adjacent substituents do not experience severe, mutual steric interactions. The effect of a substituent is always greater when at an a- rather than a /3-position. Frequency shifts from 3496 cm-1 are listed in Table 26. 

The preferred and also the most effective thermal stabilizers for nylon subjected to hot-stretching in tire cord manufacturing are salts and organic derivatives of copper (43-47). The copper salt is added before polymerization at concentrations that give 30- to 70-ppm Cu in the spun yarn. Alkali metal iodides or bromides are also added at 0.1-0.3% for synergism and stabilization of the... 

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