Elastic Properties of Well-Characterized Ethylene-Propylene Copolymer Networks

Pearson, Dale S.; Graessley, William W.

doi:10.1021/ma60076a047

Cited by 141 publications

(43 citation statements)

References 12 publications

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“…Similar comments have been found to apply 23 to ethylenepropylene networks. 26 These results therefore strongly support Flory's contention 14 that the unusually high values of the modulus reported 13 • 26 for some networks should be attributed to reinforcing effects from network crystallization rather than to highly speculative contributions from inter-chain entaglements. 56 -63 It would thus seem to be extremely difficult to use cis-trans butadiene 13 or ethylene-propylene 26 elastomers for evaluating the molecular theories of rubberlike elasticity, at least when the networks are in the unswollen state.…”

Section: 0supporting

confidence: 74%

Photoelastic Studies of Some Polybutadiene Networks

Mark

Llorente

1981

Polym J

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ABSTRACT:Two butadiene polymers were used in this investigation, one with 98.5% cis-1,4 units and the other with an approximately equibinary mixture of cis and trans units. Elastomeric networks prepared from these polymers were studied in elongation, in both the swollen and unswollen states over the temperature range -30 to 95°C. There is evidence for crystallization in these networks, particularly as manifested by marked increases in birefringence at relatively low elongations and at temperatures as high as 40°C. As expected, the birefringence and related quantities were found to be more sensitive to crystallization than the force, with the opticalconfiguration parameter and the stress-optical coefficient showing the greatest sensitivity. In the case of the cis-trans copolymer, the crystallization involves trans sequences, which are of relatively high melting point, and thus occurs at a temperature higher than for the lower melting cis sequences in the high-cis networks. The results which were free from the effects of network crystallization were used to calculate values of the temperature coefficient of the unperturbed dimensions of the chains, and values of the optical-configuration parameter. These configuration-dependent properties were found to be in satisfactory agreement with previously published theoretical results based on a rotational isomeric state model of these chain molecules.

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Section: 0supporting

confidence: 74%

Photoelastic Studies of Some Polybutadiene Networks

Mark

Llorente

1981

Polym J

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“…The pronounced time (or frequency) dependences of mechanical functions observed with loosely crosslinked networks in the rubberlike region, are connected, on one hand with the considerable length of elastically active network chains (EANCs) and their distribution, and, on the other, with the existence of topological interchain interactions (entanglements) in the network. These interactions cause long times to appear in the relaxation or retardation spectrum [1,7] and may also contribute to the equilibrium modulus of the network (Langley's concept of trapped entanglements [8]). …”

Section: Introductionmentioning

confidence: 99%

Dependence of viscoelastic spectrum width on the structure of model imperfect networks prepared by endlinking

Krakovský

Havránek

Ilavský

et al. 1988

Colloid & Polymer Sci

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Using the theory of branching processes, structural parameters such as the molecular weights of elastically active network chains (EANCs), including dangling chains, backbone EANCs and dangling chains of networks built up by the alternating polyaddition of a bi-and trifunctional monomer, are characterized. The theory is compared with viscoelastic data on polyurethane networks prepared from poly(oxypropylene)triols and diisocyanate at various initial ratios of functional groups; in the calculation, the distribution of functionalities of the triols used and the possible incompleteness of the reaction is taken into account. The comparison reveals that both the length of the backbone EANC and the length of dangling chains contribute to the total width of the retardation spectrum.

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“…Such result has been found repeatedly in the past when comparing physical measurements with different theoretical predictions, most recently [23] with the Edwards-Vilgis slip-link theory [22]. This has been commonly interpreted as being due to the presence, in the network, of trapped chain entanglements which behave more or less as ordinary network junctions-covalent crosslinks [9,23,[27][28][29][30][31][32][33][34]. Let us denote the contribution of trapped entanglements to the connectivity term as affine entanglement modulus, (2C 1 KnRT), or, alternatively, phantom entanglement modulus (2C 1 KxRT).…”

Section: Parameters and Structurementioning

confidence: 72%

A Langevin-elasticity-theory-based constitutive equation for rubberlike networks and its comparison with biaxial stress–strain data. Part II

Meissner

Matějka

2004

Polymer

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A structure-based constitutive equation for rubberlike networks (ABGIL) was proposed in Part I of this communication. It is a combination of the connectivity term based on Langevin statistics (Arruda and Boyce, AB) and a constraint term which follows from some theoretical treatments and may be expressed in the form of the first invariant of the generalized deformation tensor (GI). The ABGIL equation was tested in Part I using published biaxial stress-strain data on networks of natural and isoprene rubbers and further tests are performed in Part II on networks of poly (dimethylsiloxane) and styrene-butadiene rubber. Parameters of the equation were obtained from the fitting procedure. Apart from the region of very low (!10%) strains, a good, or even very good description (less than 5% deviation) of the experimental biaxial stress-strain behavior was obtained. In the region of very high strains, the previously introduced concept of a strain-dependent finiteextensibility parameter was applied. The effects of polymer and network structure and presence of a diluent in the course of endlinking on the fitted parameter values are discussed. The values of the exponent n in the constraint term were found to lie in a rather wide range (K0.2 to C 1) which includes predictions of four different tube theories. q

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Elastic Properties of Well-Characterized Ethylene-Propylene Copolymer Networks

Cited by 141 publications

References 12 publications

Photoelastic Studies of Some Polybutadiene Networks

Photoelastic Studies of Some Polybutadiene Networks

Dependence of viscoelastic spectrum width on the structure of model imperfect networks prepared by endlinking

A Langevin-elasticity-theory-based constitutive equation for rubberlike networks and its comparison with biaxial stress–strain data. Part II

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