Poly stress-strain curves

Anthony, Caston, and Guth obtained considerably better agreement between the experimental stress-strain curve for natural rubber similarly vulcanized and the theoretical equation over the range a = 1 to 4. KinelP found that the retractive force for vulcanized poly-chloroprene increased linearly with a — l/a up to a = 3.5. 

Figure 10.8 Stress-strain curves for 6% crosslinked poly(n-butyl acrylate) elastomer for the sample and control specimen (strain rate= lOOmm/min, room temperature). Adapted from Kushner et al. (2007). Copyright 2007 American Chemical Society.

Figure 10.4 Stress-strain curves for control and modular polymers. The curve in the bottom (—) is for the polyurethane (PU) made fiom poly(tetramethylene glycol) and...

Figure 3. Stress-strain curves of three gradient polymers and one interpenetrating network of poly(methyl methacrylate) with 2-chloroethyl acrylate at comparable strain rates of 2-3% /sec and same temperature of 80° C. The numerals in parentheses indicate concentrations (mole percent) of chloroethyl acrylate in poly(methyl methacrylate).

Notwithstanding this great variety of mechanical properties the deformation curves of fibres of linear polymers in the glassy state show a great similarity. Typical stress-strain curves of poly(ethylene terephthalate) (PET), cellulose II and poly(p-phenylene terephtha-lamide (PpPTA) are shown in Fig. 13.89. All curves consist of a nearly straight section up to the yield strain between 0.5 and 2.5%, a short yield range characterised by a decrease of the slope, followed by a more or less concave section almost up to fracture. Also the sonic modulus versus strain curves of these fibres are very similar (see Fig. 13.90). Apart from a small shoulder below the yield point for the medium- or low-oriented fibres, the sonic modulus is an increasing, almost linear function of the strain. 

FIGURE 13-44 Stress/strain curves for poly(methyl methacrylate) as a function of temperature [redrawn from an original figure by T. S. Carswell and H. K. Nason, Symposium on Plastics, American Society for Testing Materials, Philadelphia (1944)J. 

Figure 7 shows the stress-strain curves for the three polymers (23, 24). As seen from the initial slopes of the curves, the Young s moduli of these polymers are similar ( 500 MPa). In contrast, their elongations at break point are significantly different. Thus, poly(3) is rather hard and brittle, whereas poly(4a) is fairly ductile. 

Figure 7. Stress-strain curves of Si-containing poly acetylenes at 25 °C and 86% I min. (Reproduced from reference 23. Copyright 1986 American Chemical...

The mechanical properties of a craze were first investigated by Kambour who measured the stress-strain curves of crazes in polycarbonate (Lexan, M = 35000) which had first been grown across the whole cross-section of the specimen in a liquid environment and subsequently dried. Figure 25 gives examples of the stress-strain curves of the craze determined after the 1st and 5th tensile loading cycle and in comparison the tensile behavior of the normal polymer. The craze becomes more and more elastic in character with increasing load cycles and its behavior has been characterized as similar to that of an opencell polymer foam. When completely elastic behavior is observed the apparent craze modulus is 25 % that of the normal poly-... 

The most common type of stress-strain tests is that in which the response (strain) of a sample subjected to a force that increases with time, at constant rate, is measured. The shape of the stress-strain curves is used to define ductile and brittle behavior. Since the mechanical properties of polymers depend on both temperature and observation time, the shape of the stress-strain curves changes with the strain rate and temperature. Figure 14.1 illustrates different types of stress-strain curves. The curves for hard and brittle polymers (Fig. 14.1a) show that the stress increases more or less linearly with the strain. This behavior is characteristic of amorphous poly-... 

Figure 14.25 Stress-strain curves for poly(methyl methacrylate) (PMMA) in...

All tensile measurements were performed by the authors with microtomed ribbons of 0.1 mm thickness at ambient temperature. In Fig. 10 typical stress-strain curves for all three poly(ether ester) materials are plotted. All samples were extruded at a common undercooling of 60 °C. The initial tensile modulus increased from 14 MPa for material A to 62 MPa and 208 MPa for B and C, respectively. 

Fig. 10. Stress-strain curves of extrudates for poly(ether ester)s A, B and C. Initial sample length 25 mm, strain rate 1 mm/s, 25 °C, nominal extrusion ratio 4, undercooling 60 °C (for sample description see Table 4) >...

Figure 2. Stress/strain curve for a poly DCHO fibre.

Polymers such as polystyrene and poly(methyl methacrylate) with a high E at ambient temperatures fall into the category of hard brittle materials which break before point Y is reached. Hard tough polymers can be typified by cellulose acetate and several curves measured at different temperatures are shown in Figure 13.16(a). Stress-strain curves for poly(methyl methacrylate) are also shown for comparison [Figure 13.16(b)]. 

Figure 11-16. Stress/ strain curves for a poly(vinyl chloride) at temperatures between —40° C and +80° C. (After R. Nitsche and E. Salewski.) The samples appear to be brittle at —40°C, to be ductile (tough) from -20 to 23° C, to show cold flow from 40 to 60° C, and are rubberlike at 80° C.

The changes in mechanical prop>erties that are produced by loading different amounts of poly pyrrole nanopartides can be well imderstood from stress-strain curves of PP/PPy nanocomposites which are illustrated in fig 8. through 3.8. As it is clearly observed in stress-strain curves of nanocomposites, addition of polypyrrole nanopartides makes... 

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