Glassy and Polymer Dynamics of Elastomers by ¹H-Field-Cycling NMR Relaxometry: Effects of Fillers

Abstract

1 H spin–lattice relaxation rate ( R 1 ) dispersions were acquired by field-cycling (FC) NMR relaxometry between 0.01 and 35 MHz over a wide temperature range on polyisoprene rubber (IR), either unfilled or filled with different amounts of carbon black, silica, or a combination of both, and sulfur cured. By exploiting the frequency–temperature superposition principle and constructing master curves for the total FC NMR susceptibility, χ″(ω) = ω R 1 (ω), the correlation times for glassy dynamics, τ s , were determined. Moreover, the contribution of polymer dynamics, χ pol ″ (ω), to χ″(ω) was singled out by subtracting the contribution of glassy dynamics, χ glass ″ (ω), well represented by the Cole–Davidson spectral density. Glassy dynamics resulted moderately modified by the presence of fillers, τ s values determined for the filled rubbers being slightly different from those of the unfilled one. Polymer dynamics was affected by the presence of fillers in the Rouse regime. A change in the frequency dependence of χ pol ″ (ω) at low frequencies was observed for all filled rubbers, more pronounced for those reinforced with silica, which suggests that the presence of the filler particles can affect chain conformations, resulting in a different Rouse mode distribution, and/or interchain interactions modulated by translational motions.

Influence of Resins on the Structure and Dynamics of SBR Compounds: A Solid-State NMR Study

“…Therefore, FC NMR has proven to be an effective technique to characterize the dynamics of polymers far above glass transition over a broad range of characteristic motion times [47,48]. In particular, it has been successfully applied to obtain information on segmental and polymer dynamics in polymer melts and vulcanized rubbers [49][50][51][52][53][54]. For this aim, R 1 (ω) data are usually transformed to the susceptibility representation, χ"(ω) = ω R 1 (ω), and χ"(ωτ s ) master curves are built from χ"(ω) curves acquired at different temperatures by exploiting the frequency-temperature superposition (FTS) principle [55,56] to determine the values of the correlation time for segmental dynamics, τ s .…”

Peroxide‐based crosslinking of solid silicone rubber, part II: The counter‐intuitive influence of dicumylperoxide concentration on crosslink effectiveness and related network structure

“…31 The presence of a mineral filler dispersed into the rubber matrix and its influence on the nucleation phase of temperature-induced crystallization is still unclear. Even though it is reported that filler particles affect polymer chain conformations and local reptation, 32 the effect they have on nucleation is argued to be negative by some authors, 33 since fillers create a region with hindered mobility where the nucleation and crystallite growth are slowed down; neutral by others, 34 claiming that fillers extensively affect only the crosslinking reaction, not the crystallization; and positive by some, 35 that suggest fillers favor the formation of nuclei via polymer chain adsorption, interaction, or even confinement of macromolecules inside a filler network.…”

Exploring the Effect of Resins of Different Origin on the Structure, Dynamics and Curing Characteristics of SBR Compounds

“…Solid-state nuclear magnetic resonance (SSNMR) has established itself as one of the most powerful techniques for the characterization of polymer structure and dynamics [36][37][38]. In the case of elastomeric materials, 1 H spin-lattice (T 1 , T 1ρ ), spin-spin (T 2 ) relaxation times, and residual 1 H-1 H dipolar couplings have proved to be valuable tools to disclose the effects of different formulations and vulcanization conditions on the structural and dynamic properties of the polymer network [39][40][41][42][43][44]. In a recent work by some of the authors, SSNMR was employed to study styrene-butadiene rubber (SBR) compounds of technological interest for the tire industry, before and after the addition of the petroleumderived tackifying resin Kristalex™ 5140 [44].…”