Polyvinyl chloride stress-strain curve

FIGURE 38.2 Stress-strain curves of polyvinyl chloride-ground rubber tire (PVC-GRT) and PVC-Cl-GRT blends. (Reprinted from Naskar, A.K., Bhowmick, A.K., and De, S.K., J. Appl. Polym. ScL, 84, 622, 2002. With permission from Wiley InterScience.)... 

It is customary when evaluating plasticizers in polyvinyl chloride to compare them at concentrations which produce a standard apparent modulus in tension, as measured at room temperature. Since the stress-strain relationship is generally nonlinear it is necessary to specify a given point on the stress-strain curve as well as the rate of loading or straining. The efficiency may be expressed as the concentration of a given plasticizer necessary to produce this standaid modulus. Other properties, e g., indentation hardness, may take the place of tensile modulus. 

Figures 18.19, 18.20, 18.21 and 18.22 show creep curves, isochronous stress-strain curves, and stress-time curves, for a typical acrylonitrile-butadiene-styrene (ABS) terpolymer and a typical unplasticised polyvinyl chloride (PVC).

One way to obtain long-term information is through the use of the time-temperature-superposition principle detailed in Chapter 7. Indeed, J. Lohr, (1965) (the California wine maker) while at the NASA Ames Research Center conducted constant strain rate tests from 0.003 to 300 min and from 15° C above the glass transition temperature to 100° C below the glass transition temperature to produce yield stress master curves for poly(methyl methacrylate), polystyrene, polyvinyl chloride, and polyethylene terephthalate. It should not be surprising that time or rate dependent yield (rupture) stress master curves can be developed as yield (rupture) is a single point on a correctly determined isochronous stress-strain curve. Whether linear or nonlinear, the stress is related to the strain through a modulus function at the yield point (mpture) location. As a result, a time dependent master curve for yield, rupture, or other failure parameters should be possible in the same way that a master curve of modulus is possible as demonstrated in Chapter 7 and 10. 

Figure 12.22 Measured ratio of yield stress to temperature as a function of logarithm of strain rate for polyvinyl chloride. The set of parallel curves is calculated from Equation (12.22). (Redrawn from Bauwens-Crowet, C., Bauwens, j.A. and Homes, G. (1969) Tensile yield-stress behavior of glassy polymers. J. Polym. Sci. A2,7, 735. Copyright (1969) John Wiley Sons, Inc.)...

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