Rheological and solid wall boundary condition characterization of unvulcanized elastomers and their compounds

Abstract

SynopsisAn extensive fundamental investigation of the rheological properties and solid wall boundary condition shear stress of elastomers and elastomer-carbon black compounds has been carried out.T h e elastomers were an emulsion butadiene-styrene copolymer (SBR 1500) and a polybutadiene.Shear flow rheological properties were measured using a newly designed sandwich rheometer, in both constant shear rate and creep modes as well as in a capillary rheometer. A constant elongation rate rheometer for elastomers was developed. Stress relaxation measurements were also carried out in the sandwich rheometer. The shear viscosity of the gum elastomers exhibits a constant very high shear zero viscosity (8 X lo8 Pa.s for SBR 1500 at 100°C) and decreases with increasing shear rate. The compounds exhibit yield values of similar magnitude to carbon black compounds of molten plastics. Only the SBR 1500 and its compounds were studied in the elongational flow mode. It was not possible to achieve a steady state in these experiments. An apparatus for measurement of shear stress as a function of velocity (shear rate) a t a specified pressure was developed. The instrument, which we call a friction tester, was used not only to determine wall shear stress but to investigate the regime of flow and potentially determine conditions for the onset of slip. Evidence of changing flow regimes were found, and the implications discussed.

Correlations in rheological behavior between large amplitude oscillatory shear and steady shear flow of silica‐filled star‐shaped styrene‐butadiene rubber compounds: Experiment and simulation

“…Extensive investigations have been carried out on the steady shear flow behavior of CB‐filled rubber 1–4,31,33–45 . These studies noted strong shear thinning behavior and an increase in viscosity with CB loading and surface area.…”

Effect of volume loading and surface treatment on the thixotropic behavior of polypropylene filled with calcium carbonate

“…Polymer melts and elastomers containing high volume loadings of small particles are well known to exhibit rather different rheological properties than their Newtonian counterparts. Most strildng are (i) the existence of yield values in both shear and elongational flows ( [6][7][8][9][10][11][12][13][14], (ii) solid-like responses to sinusoidal oscillations (9,14). (iii) the reduction of elastic recovery following flow and extrudate swell (7-9, 15, 16), and (iv) long duration time dependent behavior arising from thixotropy as well as viscoelasticity.…”

Steady State and Dynamic Oscillatory Shear Properties of Carbon Black Filled Elastomers

“…For carbon black with nitrogen adsorption above ~25 m 2 /g and volume loading above ~13%, the filler reinforcement effect becomes significant. [26][27][28] Figure 2.2. Idealized form of shear modulus vs strain curve (Reprinted with permission from Ref.…”

“…It is well known that the addition of reinforcing carbon black, which is to say carbon black with particle size less than 90 nm, above a volume loading of ~13% leads to an increase in the storage and loss moduli and a decrease in the critical strain amplitude associated with the linear viscoelastic region. 6,[19][20][21][26][27][28] With further increases in strain beyond the linear viscoelastic region, the well documented Payne effect is observed, in which the storage modulus decreases with increasing strain. 24 The effects of carbon black on the nonlinear response of filled rubbers have been studied using stress shape analysis and Fourier transform analysis, but are not fully understood.…”