Double Yielding in a Styrene/Butadiene Star Block Copolymer

Adhikari, Rameshwar; Buschnakowski, M.; Henning, Sven; Goerlitz, S.; Huy, Trinh An; Lebek, Werner; Godehardt, R.; Michler, G. H.; Lach, Ralf; Geiger, K.; Knoll, Konrad

doi:10.1002/marc.200300186

Cited by 49 publications

(37 citation statements)

References 20 publications

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“…This special morphology is a consequence of its special molecular architecture. 19,20 It is known that the low molar mass homopolymer can swell the corresponding block domains, leading to a transition in morphologies. 1 Assuming the structure of the star block copolymer to be intermediate between the PS cylinders and alternating lamellae, one may expect that cylinders and spheres of PS will be formed by adding different amounts of low molar mass PS004, as the latter practically increases the effective soft phase volume fraction.…”

Section: Morphology Of Block Copolymer/homopolymer Blendsmentioning

confidence: 99%

“…19 The tensile stress-strain curves of the star block copolymer and its blends with PB004 and PS010 are shown in Figure 2. Owing to its morphology, comprising the cocontinuous network of PS and PS-co-PB, the star block copolymer behaves in a ductile manner (curve 3 in Fig.…”

Section: Tensile Mechanical Propertiesmentioning

confidence: 99%

“…Details on the characterization of the copolymer have been reported elsewhere. 18,19 The polystyrene homopolymer (PS010; courtesy of Dr. Marc Langela, Max Planck Institute for Polymer Research, Mainz), prepared by anionic polymerization, has a number average molecular weight (M n ) of 9800 g/mol and a polydispersity index (M w /M n ) of 1.06. The polybutadiene homopolymer (PS004) used has a number average molecular weight (M n ) of about 4000 g/mol.…”

Section: Materials and Sample Preparationmentioning

confidence: 99%

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Relationship between nanostructure and deformation behavior of microphase‐separated styrene/butadiene systems

Adhikari

Lebek

Godehardt

et al. 2006

J of Applied Polymer Sci

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ABSTRACT:The relationship between the morphology and the mechanical properties of nanostructured blends, comprising an asymmetric styrene/butadiene star block copolymer, exhibiting cocontinuous-like morphology and low molar mass homopolymers, was studied by electron microscopy, microindentation hardness, and tensile testing methods. Results show that the deformation behavior of these systems is significantly modified by the presence of unentangled homopolymer chains, leading partly to a decrease in mechanical properties. In contrast to common polymer blends, in which usually, the hardness values do not markedly deviate from the additivity law, the H-values in the system investigated show large deviations from the linear additivity behavior. The observed anomalous behavior is discussed in terms of the enhanced local flow processes induced by the phase-separated morphology at a nanometer scale.

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Section: Morphology Of Block Copolymer/homopolymer Blendsmentioning

confidence: 99%

Section: Tensile Mechanical Propertiesmentioning

confidence: 99%

Section: Materials and Sample Preparationmentioning

confidence: 99%

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Relationship between nanostructure and deformation behavior of microphase‐separated styrene/butadiene systems

Adhikari

Lebek

Godehardt

et al. 2006

J of Applied Polymer Sci

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“…However, the existence of double yielding in nanostructured amorphous polymer was reported recently. 22 The shape of the stress-strain curve (s-e) in the double yield region may exhibit comparable values of the stress of the two maxima or a dominant value of either maximum. The stress of the first yield process becomes dominant under extreme conditions of low temperatures, high strain rates, or high crystallinities.…”

Section: Introductionmentioning

confidence: 99%

Crystallinity variations in the double yield region of polyethylene

Manzur

Rivas

2007

J of Applied Polymer Sci

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Numerous specimens of a linear low density polyethylene sample were uniaxially deformed up to different elongations to study the double yield phenomenon. Extruded samples were analyzed to calculate the crystallinity and to estimate the mean crystal size, under stressed state and released state (after removal of the stress), using the wide angle X-ray scattering technique. The crystallinity degree and the mean crystal dimension associated to the (110) orthorhombic reflection of the specimen without deformation were of 55% and 16 nm. These parameters in the stressed state, as functions of the elongation, presented a multi-step behavior. A decrement after the first yield point (48%, 13 nm), then another decrement, and an abrupt increment followed by a decrement at higher strain values around the second yield point (28, 40, and 30%; 12, 14.5, and 11 nm). The behavior was more notorious in the stressed state than in the released state. The latter results were interpreted in terms of a partial melting followed by a recrystallization process. These experimental findings show that the second yield is not only associated with the deformation of the crystalline region. This partial meltingrecrystallization process is one of the main mechanisms of the double yield phenomenon.

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“…[5] To date, various studies have shown the existence of the double yielding phenomenon. [6][7][8][9][10][11][12][13] Segulea et al have observed the double yield behavior of several PE and related copolymers. [6] Plaza et al have studied the double yield points in triblends of low density PE, linear low density PE and EPDM, and observed that the double yield phenomenon decreased until it disappeared with increasing EPDM component.…”

Section: Introductionmentioning

confidence: 99%

Morphology Dependent Double Yielding in Injection Molded Polycarbonate/Polyethylene Blend

Huang

Yang

et al. 2004

Macro Materials & Eng

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Summary: Polycarbonate (PC)/polyethylene (PE) blend was injection molded at different molding temperatures. The morphological observation by scanning electronic microscope (SEM) indicated that the sample molded at 190 °C contained only uniformly dispersed spherical PC particles. The samples molded at 230 and 275 °C had a typical skin‐core structure, and there were many injection‐induced PC fibers in the subskin. While the sample molded at 190 °C had the usual stress‐strain behavior, the samples obtained at 230 and 275 °C showed apparently double yielding behavior. It was suggested that the double yielding points were morphology‐dependent. The first one was the result of the yielding of PE at low strain, and the second one was caused by the yielding of the PC fibers. Moreover, it is the frictional force in the interfaces between PC and PE that transferred the stress to the PC fibers, hence giving rise to the reinforcement of PE by PC.Stress‐strain curves of PC/PE blends injection molded at various temperatures showing first (I) and second (II) yielding points.magnified imageStress‐strain curves of PC/PE blends injection molded at various temperatures showing first (I) and second (II) yielding points.

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Double Yielding in a Styrene/Butadiene Star Block Copolymer

Cited by 49 publications

References 20 publications

Relationship between nanostructure and deformation behavior of microphase‐separated styrene/butadiene systems

Relationship between nanostructure and deformation behavior of microphase‐separated styrene/butadiene systems

Crystallinity variations in the double yield region of polyethylene

Morphology Dependent Double Yielding in Injection Molded Polycarbonate/Polyethylene Blend

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