A critical analysis of the effect of crosslinking on the linear viscoelastic behavior of styrene–butadiene rubber and other elastomers

Abstract

The linear viscoelastic behavior in dynamic shear and tensile creep at temperatures from À30 to 70 C is measured for an styrene-butadiene rubber (SBR) elastomer cured with dicumyl peroxide to crosslinking densities between 0 and 23.5 Â 10 À5 mol/cm 3 . The G 0 , G 00 , and tan d isotherms are analyzed by time-temperature superposition (TTS), where the tan d master curves are consistent with those of Mancke and Ferry. However, to achieve the TTS in the lightly crosslinked SBR systems, an anomalous vertical shift is required in the narrow temperature region from 10 to 30 C. The vertical shift factor in this temperature region is not the standard q 0 T 0 =qT from rubber elasticity. No anomalous behavior is detected in the equilibrium modulus, which is a linear function of temperature in accordance with the classical theory of rubber elasticity. In contrast to SBR, standard vertical shifts are required to effect TTS for uncrosslinked polybutadiene and an ethylene propylene diene monomer elastomer.

Two coupled effects of sub micron silica particles on the mechanical relaxation behavior of ethylene–propylene–diene rubber chains

“…9 Crosslinking has an obvious effect on the mobility and relaxation of macromolecular chains. 21 For vulcanized rubber and uncrosslinked polymer, the biggest difference is the vulcanization process. So, the incorporation of inorganic particles into the rubber matrix, on one hand, directly inuences the mobility and relaxation of the chains for the same case in the un-crosslinked polymer composites; on the other hand, the inorganic particles may also induce changes in the crosslinked network and then further inuence the molecular mobility of rubber chains.…”

Effect of Cross-Linking Density on Horizontal and Vertical Shift Factors in Linear Viscoelastic Functions of Epoxy Resins

“…Thus, we here adopted a safer procedure where a master curve of tan δ (= E ″/ E ′) is constructed by first shifting the data horizontally to determine a T and then vertically to determine b T . The determination of a T based on the tan δ curve increases the accuracy for the superimposition procedure because the vertical shift is less important and not always necessary. , …”

“…Although the physical origin of the vertical shifting has been hitherto discussed, ,, it seems that the most plausible concept is based on the Rouse model, where the complex modulus is scaled with the temperature and mass density as follows: ,, where ρ­( T ) and ρ­( T r ) are the mass densities at T and T r ( T g in this study), respectively. Figure shows the correlation between b T and T – T g (Δ T ) for ER12, ER10, ER8, ER6, ER4, and ER2.…”

“…The TTS principle is based on the assumption that the temperature has the same effect on a relaxation process . So far, great efforts have been made to examine whether the TTS principle was applicable to various types of polymer systems such as polymer melts, − blends, − and composites. − Through these works, the time (frequency) and temperature ranges, in which the TTS principle held (or broke down), have become clear. However, there have been few studies dealing with the verification of TTS reliability for cross-linked polymers including epoxy resins.…”

Hyper‐viscoelastic characterization of highly filled rubber compound: Extending approach for geometrical defect analysis

“…In addition to hyperelastic behavior, filled rubbers exhibit relaxation, determined using viscoelastic constitutive relationships. [14,30,31] The viscoelastic behavior becomes dominant when the larger extension is considered. [32] The viscoelastic constitutive models assume distributed nonlinear elastic springs combined with the distributed Maxwell elements described as Prony series.…”