Stress-temperature curves

The methods discussed so far have been concerned with the presentation of combined creep data obtained at a single temperature. Thus, a further method is required to indicate the influence of tanperature. 

One convenient method is to combine the information available from isochronous stress-strain curves or stress-time curves obtained on the same materials at different tanperatures. For example, suppose the performance criterion for a particular application is that the total strain should be 2% in 1,000 h. Using the 1,000 h isochronous stress-strain curve for each temperature and erecting an ordinate at the 2% point on the strain axis, the individual working stresses for each temperature can be obtained. Alternatively, by erecting an ordinate at the 1,000 h point on the stress-time curve 

By a similar procedure, stress-temperature plots for other spedfictime-permissible strain combinations can be obtained. 

---

The product of the elastic modulus and thermal-expansion coefficient for the thin polymer coating, Ea, can be calculated from the stress-temperature curve by the... 

Thus, Ea of the polymer is proportional to the slope of the stress-temperature curve in thermal-expansion dominated regimes. A decrease in Ea results in a lower thermal-expansion-mismatch induced stress. Thus, a lower Ea should also endow the material with the ability to sustain a greater number of thermal cycles before fatigue-induced fracture because of a smaller cyclical stress amplitude. 

Figure 6-1. Stress-temperature curves of natural rubber. Extension ratios X are indicated on the right of the figure. [After M. Shen, D. A. McQuarrie, and J. L. Jackson, J. Appl. Phys., 38, 791 (1967), by permission of the American Institute of Physics.]...

Fig. 6. Yield-stress-temperature curves of different flexibilized EP s.

Fig. 10. Stress-temperature curves for sulfur-vulcanized natural rubber (99,103). Courtesy of the American Chemical Society.

In Chapter 18 is discussed the measurement of mechanical, electrical and optical properties of polymers. Mechanical measurements include measurement of load bearing characteristics of polymers including stress/strain curves, stress temperature curves, recovery and rupture. Also measurement of impact strength characteristics by Izod and falling weight methods and many other polymer characteristics for polymer sheet, pipe, film, powders and rubbers and elastomers. 

Figure 18.13 Interpolated stress-temperature curves of polyethylenes of different densities (2% total strain at 1000 hours). Source Author s own files)...

Figure 18.14 Interpolated stress-temperature curves for various grades of polypropylene (0.5% total strain at 1000 hours). KMT 61 and GMT 61 = polypropylene copolymers, KM 61, GM 61 and DE 61 = polypropylene copolymers.

FIGURE 2.11 Interpolated stress-temperature curves of various grades of PP (0.5% total strain at 1,000 h). DE 61 = PP copolymers. 

Figure 12 Stress-temperature curves at constant pressure and length for an amorphous polyethylene network in the unswollen state. Values of the elongation a and of the nominal stress / are calculated using the rest length and the undeformed cross-section respectively, at the highest temperature investigated (reproduced by permission of Wiley from J. E.

---