Long time stress relaxation of amorphous networks under uniaxial tension: The Dynamic Constrained Junction Model
Konyalı, Haluk and Menceloğlu, Yusuf Z. and Erman, Burak (2008) Long time stress relaxation of amorphous networks under uniaxial tension: The Dynamic Constrained Junction Model. Polymer , 49 (4). pp. 1056-1065. ISSN 0032-3861
Official URL: http://dx.doi.org/10.1016/j.polymer.2008.01.011
Poly-isoprene networks with different degrees of cross-linking and filler amount are studied under uniaxial stress relaxation. Time decay of stress obeys a stretched exponential form with a stretching parameter of 0.4 that is same for all independent variables, i.e., extensions, crosslink density and filler amount. Relaxation time τ increases with increasing strain, and decreases with both cross-link and filler content. Dependence of τ on filler content is less sensitive than on cross-link density. The isochronous Mooney-Rivlin plots show that the phenomenological constant 2C1 is time independent, and all time dependence results from that of 2C2 , which is associated with relaxation of intermolecular interactions at and above the length-scales of network chain dimensions. The relatively low value of the stretching parameter is interpreted in terms of a molecular model where entanglements contribute to relaxation at a wide spectrum of time scales.
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