Structural changes in the carbon black network in carbon‐black‐filled styrene‐butadiene rubber samples cured with a two‐step process

Abstract

The volume resistivity of carbon black (CB)‐filled crosslinked styrene‐butadiene rubber (SBR) samples cured in two steps and having a fixed elongation condition declined slightly when the elongation ratio (α) was 3 or smaller, whereas the value increased markedly at α = 4. Three‐dimensional transmission electron microscopy observations revealed that the closest interparticle distance between the carbon black aggregates (CBag's) and the CBag number density decreased at α = 1−2 but increased at α = 4 and that the distance between the centers of gravity of the closest CBag and the volume of CBag increased at α = 1−3 but decreased at α = 4. Also, the fraction of crosslinked chains of the carbon black network (CBnet) was decreased with elongation, and the fraction of branched chains increased. The fraction of isolated chains in particular showed a more pronounced increase at α > 3 compared with α < 3. These results presumably imply that for the sample with α > 3, the coarsened CBag's were finely divided and also that the CBnet was broken by elongation. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Filler Network Recovery of Carbon Black Filled Rubber

“…The knowledge leads us to the idea that the change in carbon black network occurs in large deformations and it leads nonlinearity in viscoelastometry. This plausible idea has been confirmed in electric resistance measurements of filled rubbers 6) and 3D-TEM observation of filled rubbers cured in deformed states 23) .…”

Filler Effects on Temperature Shift Factors in Viscoelastic Properties of Carbon Black Filled Rubbers

“…3 nm and it changes due to large deformation which is observed by 3D-TEM. 10,11) Bridged filler network has not been confirmed by experiment. However, it may be plausible, because of the next points.…”

“…Generally speaking, there exist some networks in practical soft materials. Recently existence of filler network in filled rubbers has been recognized experimentally not only in macroscopic scale by rheometry in reversing double-step deformations 3) and electric resistance measurement 4) but also in microscopic scale by in-situ microscopy 5,6) and 3D-TEM [7][8][9][10][11] .…”

“…Polymer-bridged filler network may be based on constraint on polymer chain by filler gel (in real image, probably by trapped entanglement in filler gel phase) [11][12][13][14][15][16] Therefore, polymerbridged filler and entanglement and/or crosslinking networks are supposed to have no special contribution to temperature dependence of segmental friction.…”

Nonlinear Rheology of Rubber Materials

“…In observing the structural change in carbon black filled systems, it is highly effective to supplement measurements of large deformation response with concurrent measurements of perturbation/superimposed stimulus response and change in electrical resistance. More recently, the CB contact filler network structure under deformation has also been observed by 3D-TEM [16]. It is hoped that further progress will be made in the rheological analysis of rubber materials based on observation of structural change.…”