Copolymer stress-strain curve

Proportion of Hard Segments. As expected, the modulus of styrenic block copolymers increases with the proportion of the hard polystyrene segments. The tensile behavior of otherwise similar block copolymers with a wide range of polystyrene contents shows a family of stress—strain curves (4,7,8). As the styrene content is increased, the products change from very weak, soft, mbbedike materials to strong elastomers, then to leathery materials, and finally to hard glassy thermoplastics. The latter have been commercialized as clear, high impact polystyrenes under the trade name K-Resin (39) (Phillips Petroleum Co.). Other types of thermoplastic elastomers show similar behavior that is, as the ratio of the hard to soft phase is increased, the product in turn becomes harder. 

Density is also found to increase in this region, thus providing additional evidence of crystallisation. Certain synthetic elastomers do not undergo this strain-induced crystallisation. Styrene-butadiene, for example, is a random copolymer and hence lacks the molecular regularity necessary to form crystallites on extension. For this material, the stress-strain curve has a different appearance, as seen in Figure 7.12. 

Copolymerization of ethylene and styrene by the INSITE technology from Dow generates a new family of ethylene-styrene interpolymers. Polymers with up to 50-wt% styrene are semicrystalline. The stress-strain behavior of the low-crystallinity polymers at ambient temperature exhibits elastomeric characteristics with low initial modulus, a gradual increase in the slope of the stress-strain curve at the higher strain and the fast instantaneous recovery [67], Similarly, ethylene-butylene copolymers may also be prepared. 

Recent work has focused on a variety of thermoplastic elastomers and modified thermoplastic polyimides based on the aminopropyl end functionality present in suitably equilibrated polydimethylsiloxanes. Characteristic of these are the urea linked materials described in references 22-25. The chemistry is summarized in Scheme 7. A characteristic stress-strain curve and dynamic mechanical behavior for the urea linked systems in provided in Figures 3 and 4. It was of interest to note that the ultimate properties of the soluble, processible, urea linked copolymers were equivalent to some of the best silica reinforced, chemically crosslinked, silicone rubber... 

Figure 1. Stress-strain curves of polycarbonate-polydimethyl-siloxane block copolymers (Crosshead Speeds 5 cm/min). (Reproduced from Refs. 15 18. Copyright 1980, 1984 American Chemical Society.)...

Figure 10.1. USAXS observation during straining of an SBS block copolymer. Right monitor Intensity maxima on an ellipse. Raw-data coordinate system (x,y) and radial cuts for data analysis are indicated. Middle Videotaping of sample. Left Stress-strain curve. Control booth of beamline BW4, HASYLAB, Hamburg...

Figure 13.6 (a) Elongation as a function of wind-up speed for partially oriented yarn, (b-d) Stress-strain curves of fibers of PET blends with 3% copolyester of 1,4-phenyleneterephthalate and p-oxybenzoate (CLOTH) and 3% copolymer of 6-oxy-2-naphthalene and p-oxybenzoate (CO), spun at 3500, 4000 and 4500 m/min (1) PET control (2) 3 % CLOTH (3) 3 % CO the loci of the theoretical extensions of the PET control are shown as dashed curves [17]. From Orientation suppression in fibers spun from melt blends, Brody, H., J. Appl. Polym. Sci., 31, 2753 (1986), copyright (1986 John Wiley Sons, Inc.). Reprinted by permission of John Wiley Sons, Inc. 

Likewise, the mechanical properties of the copolymers were nearly identical or even somewhat enhanced towards the polyimide homopolymer in terms of the modulus and tensile strength values [44,47]. For most of the block copolymers, the elongations to break were substantially higher than that of PMDA/ODA polyimide (Table 4). The shape of the polyimide stress-strain curve is similar to that of a work-hardened metal with no distinguishable yield point... 

The production and properties of ethylene homo- and copolymer foams with densities less than 50 kg/cu.m. are reviewed. A brief historical summary is given, followed by a discussion of six key parameters as they relate to the properties and form of the foam. The diversity of the manufacturing processes available for foam production is illustrated by three distinct operating techniques. Stress-strain curves are used to demonstrate the wide spectrum of properties obtainable and examples of applications are given. 11 refs. 

Figure 14. Stress-strain curves for 1 1 ethyl acrylate butyl acrylate copolymers with S16MA MACROMER at 30%, 40%, and 50% MACROMER contents.

Figure 3. Stress-strain curves for 15 and 33% acrylate copolymers...

The stress-strain curves obtained [32] for the whole series of CM I Mx as well as for PMMA, as a reference, are shown in Fig. 34. It is clear that all the CMIMx exhibit a strain softening which is more and more pronounced when the CMI content increases. Quite a similar behaviour is observed at any temperature in the range 25 to (Ta - 20) °C. It is worth noting that at lower temperatures, the CMIMx copolymers are brittle and, so, for CMIM25 the lowest possible temperature is 50 °C. 

Fig. 34 Stress-strain curves at 100 °C for PMMA and CMIM copolymers (strain rate of 2 x KT3 s 1) (From [32])...

The mechanical and rheo-optical properties of Kraton 101 have been studied by Stein136) using films cast from methylethyl ketone and from toluene solutions. The stress-strain curves, birefringence-strain curve, stress relaxation, birefringence relaxation, and dynamic mechanical spectra are dependent upon the morphology of the copolymer which in turn is dependent upon the conditions of preparations of the samples. 

Fig. 23. Stress-strain curves of PS and of SAN copolymers with varying AN content obtained at a displacement rate of 5.08 x 10 cm/min...

A detailed study of SB diblock copolymers and diblock/homopolymer blends was conducted in the range of composition in which the polybutadiene cylindrical morphology prevails Stress-strain experiments on a series of samples revealed dramatically varying behavior from essentially brittle response to substantial and attractive levels of toughness. Figures 2a to 2d provide representative stress-strain curves for the initial morphologies shown in Figs. 3a-3d. Table 1 provides the relevant molecular level information for these blends. 

Fig. 8. Stress-strain curves of six different diblock copolymer blends tested at 20 °C. For molecular and morphological details see Tables 1 and 2...

Since ABS copolymer has a large deformability associated with a poor thermal conductivity, the total work done on a specimen during the loading process may convert to deformation heat, which affects ABS flow behaviour, particularly at a high strain-rate loading. Thus, the effect of temperature rise during deformation must be taken into craisideration. From the tme stress-strain curves of Fig. 1, the temperature rise in a specimen can be calculated as a function of strain for each strain-rate level by an integral form of... 

Fig. 19. The stress-strain curves recorded for the two triblock copolymer samples during cold drawing of films with a constant rate of 1 mm/min. ABA-isolated clean pnBA central block Mn=65,200 pMMA outer blocks, Mn=13,150, overall Mw/Mn=1.34. ABA-sequential clean pnBA central block, Mn=67,500 pMMA-grad-pnBA outer blocks 13mol% nBA and 87 mol% MMA, Mn=10,600, overall Mw/Mn=1.24. Inset small angle X-ray scattering intensities for these samples. Reprinted with permission from [94]. Copyright (2000) John Wiley Sons, Inc.

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