Elastomeric networks, bimodal

Equi-biaxial extension results have been obtained by inflating sheets of unimodal and bimodal networks of PDMS [114,115]. Upturns in the modulus were found to occur at high biaxial extensions, as expected. Also of interest, however, are pronounced maxima preceding the upturns. Such dependences represent a challenging feature to be explained by molecular theories addressed to bimodal elastomeric networks in general. 

Von Lockette, P. R. Arruda, E. M. Wang, Y., Mesoscale Modeling of Bimodal Elastomeric Networks Constitutive and Optical Theories and Results. Macromolecules 2002, 35, 7100-7109. 

Sur, G. S. Mark, J. E., A Novel Method for Preparing Bimodal Elastomeric Networks. Polym. Bull. 1985,13, 505-509. 

Mark, J. E., Effect of Swelling on the Short-Chain Reinforcement Observed in Bimodal Elastomeric Networks. Macromolecules 1984,17 (12), 2924-2925. 

Hanyu, A. Stein, R. S., Segmental Orientation and Infrared Dichroism of Model Bimodal Elastomeric Networks. Macromol. Symp. 1991,45,189-203. 

Mark JE. Bimodal elastomeric networks. In Mark JE, Lai J, editors. Elastomers and rubber elasticity. Washington, DC American Chemical Society 1982. p. 349-66. 

Hanyu A, Stein RS. Segmental orientation and infrared dichroism of model bimodal elastomeric networks. Macromol Symp 1991 45 189-203. 

Xu P, Mark JE. Biaxial extension measurements on bimodal elastomeric networks. J Polym Sci Polym Phys Ed 1991 29 355-8. 

One of the most interesting types of model networks is the bimodal. These networks consist of very short chains intimately end-linked with the much longer chains that are representative of elastomeric materials.237,251,253,268-278 Such a network is shown in Figure 4.11,269 where the short chains are arbitrarily drawn thicker than the long ones. 

Mark, J. E., Elastomeric Networks with Bimodal Chain-Length Distributions. Acc. Chem. Res. 1994,27, 271-278. 

Sharaf, M. A. Mark, J. E. Hosani, Z. Y. A., Regular Bimodal Polydimethylsiloxane Networks. Elastomeric Properties of the Tetrafunctional Networks. 

Sharaf MA, Mark JE, Hosani ZYA. Regular bimodal polydimethylsiloxane networks. Elastomeric properties of the tetrafunctional networks. Eur Polym J 1993 29 809-17. 

Mark JE. Elastomeric networks with bimodal chain-length distributions. Acc Chem Res 1994 27 271-8. 

Elastomers cured with two crosslinking systems such as sulphur and the polymerisation products of p-benzoquinone are shown to have much improved overall mechanical properties. Non-Gaussian behaviour of quinone polymer crosslinked elastomers viewed as bimodal networks was studied. The study focused on the effect of ageing time on the reduced stress values of the networks in relation to the elongation of the samples. The study is also extended to cover the possible effect of these bound antioxidants on the onset of the vulcanisation process and the hardness values of the elastomeric networks. 15 refs. 

Tang, M.-Y. Garrido, L. Mark, J. E., The Effect of Crosslink Functionahty on the Elastomeric Properties of Bimodal Networks. Polymer 1984,25,347-350. 

Sharaf MA, Mark JE, Al-Ghazal AA-R. Elastomeric properties of poly(dimethylsiloxane) networks having high-functionality crosslinks and bimodal chain-length distributions. J Appl Polym Sci Symp 1994 55 139-52. 

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