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  • 1
    Electronic Resource
    Electronic Resource
    The mechanical properties of styrene-butadiene-styrene (SBS) triblock copolymer blends with polystyrene (PS) and styrene-butadiene copolymer (SBR) (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 673-683 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Measurements were made of linear viscoelastic properties and nonlinear stress-strain properties of phase-separated styrene-butadiene-styrene (SBS) copolymers and their blends with several homopolymer polystyrenes (PS) and one random copolymer (SBR). Torsion pendulum testing yielded shear moduli G′, G″, and Rheovibron experiments produced tensile moduli E′, E″, over a 220°K range of temperature, both at low frequencies. For pure copolymers and their PS blends, G′ and E′ correlated quite well with the total PS content, but G″ and E″ were more sensitive to how the additive was distributed. Results suggest that a PS additive whose molecular weight (M) is less than that of the copolymer PS-block (Ms) causes expansion of both the interphase and the homogeneous PS-rich phase, while an additive with M 〉 Ms mixes less well with these phases (probably forming separate domains of pure PS) and is less effective in enhancing the linear moduli. The blending with SBB produced reduction in G′ but a broad midrange peak in G″, suggesting that SBR was localized almost entirely within an expanded interphase. Tensile stress-strain data were obtained with an Material Testing System at room temperature. For PS blends, properties did not correlate well with the total PS content, the blends being always weaker than the SBS of the same overall composition. The amount of set also increased with PS content in the blends. Cyclic tests to increasing strain showed progressive structural alterations (as for the host SBS), with blend behavior resembling host properties more closely with each new cycle. When SBR was the additive, amounts as small as 1 percent reduced the curves by 15 percent. The yield stress was eliminated entirely with an addition of 10 percent SBR, but for all cases the set was the same. Results are discussed in terms of interphase force barriers to chain flow.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760221104
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  • 2
    Electronic Resource
    Electronic Resource
    Microstructural influences on volumetric properties of styrene-butadiene-styrene block copolymers (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 525-533 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A water-displacement method was used to measure the specific volume of three styrene-butadiene-styrene (SBS) block copolymers over the temperature range 4°C to 65°C. The polymers contained 0.268. 0.293, and 0.482 weight fraction polystyrene, varied in molecular weight, and are known to be phase-separated at these temperatures. Coefficients of thermal expansion were also obtained and found to be constant over this temperature range. Results are compared with various models of composite behavior, the most successful of which is the linear mixing rule which gives good predictions over this composition range. Deviations for specific volume are negative, and for expansion coefficient positive, from the linear rules. More complex behavior is suggested, however, and this is interpreted in terms of microstructural characteristics. Some apparent contradictions in data reported by other workers are explained. Results are presented also for samples stretched uniaxially up to 300 percent strain; only slight evidence of dilation is seen at 22°C. but increase of the expansion coefficient is more apparent.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760260803
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  • 3
    Electronic Resource
    Electronic Resource
    Microstructural diagnosis of block copolymer nonlinear mechanical properties I. Uniaxial stress/strain (1988)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 207-220 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An earlier study on the linear dynamic properties of triblock copolymers was continued into the nonlinear property regime. Uniaxial tensile tests were performed on styrene-butadiene-styrene block copolymers. The three polymers, having polystyrene (PS) fractions 0.27, 0.29, and 0.48, also represented three molecular weights (0.49, 0.58, and 1.0 × 105). Specimens were prepared by casting from three solvents (methyl ethyl ketone, MEK; cyclohexane; and a 9:1 mixture of tetrahydrofuran and MEK). This wide range of variables led to a correspondingly wide spectrum of properties, including the “plastic-to-rubber” transition in some cases. Stress-strain curves were characterized by modulus, yield stress, general elevation, and fracture stress and elongation. Results were interpreted in terms of microstructural parameters obtained from the earlier linear tests, including interphase properties, and molecular features as well. Special insight emerged from comparison of first-cycle (to 300 percent elongation) and second-cycle tests, including changes in modulus, yielding, level, and the appearance of set. Additional data on sample preparation influences and PS continuity effects on sample properties were also obtained.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760280404
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  • 4
    Electronic Resource
    Electronic Resource
    Microstructural diagnosis of block copolymer nonlinear mechanical properties. II: Free recovery from large tensile deformations (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 227-234 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Three styrene-butadiene-styrene (SBS) block copolymers were cast into sheet form, and the resulting microphase-separated specimens were tested in tensile free recovery. After an initial strain of 300%, specimens were released and their lengths measured for about a week. For one polymer, the recovery curves are presented for seven temperatures in the range -40 to +80°C; other data are given at 22°C. Analysis of the recovery curves, using as the model a series assembly of Kelvin elements, obtains time constants for microstructural repair and explains the temperature dependence in terms of the microstructural interphase and its partial vitrification. Differences among the three polymers can be interpreted by recognition of styrene-block molecular weights, as well as by the volume fractions of the domain styrene cores and interphases. Additional structural information arises from torsion pendulum experiments over -120 to 100°C for unstretched, stretched (300%), and partially recovered samples.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760290404
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  • 5
    Electronic Resource
    Electronic Resource
    Microstructural diagnosis of block copolymer nonlinear mechanical properties. III: Cycling tensile tests (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 235-243 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The same three styrene-butadiene-styrene copolymers discussed in the companion paper (this issue) were tested by cycling in uniaxial tension/retraction, with large magnitude (to 600% in some cases) and different sequences and rates. The behavior of “set”, at the end of each retraction, is examined in detail and invoked to explain several other features of the stress-strain curves. Time scales for structural recovery determined in the companion paper are found to assist this interpretation. Quantitative modeling of the isostructure retraction curves is accomplished in terms of the Mooney-Rivlin strain function, modified to employ a strain variable amplified by the volume of broken glassy “filler”. Values of the two Mooney moduli G1 and G2 are used to infer various features of the microstructure.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760290405
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