Elastomeric materials are nowadays of central importance in many fields of application, where they need to fulfil specific mechanical requirements. The mechanical properties of an elastomeric material take their origin on the features and topology of the polymer network. In fact fixed chemical cross-links and physical entanglements among polymer chains impose notable restrictions on chain mobility and are at the basis of rubber elasticity [1]. Moreover, a significant reinforcement effect can be achieved by incorporation in the rubber matrix of different nanoparticles, such as carbon black, carbon nanotubes, nanosilica, and clays [2, 3]. Although in the past decades extensive research efforts have been addressed to the comprehension of the relationships between "molecular" and mechanical properties of elastomeric materials, a full understanding is still far from being achieved due to the complex interplay of many different factors. In this work we investigated the structural and dynamic properties of various elastomeric materials, based on isoprene, butadiene and styrene-butadiene rubbers, with application in the tyre industry, by combining different time-domain nuclear magnetic resonance (TD-NMR) techniques. The effect of cross-linking was explored by studying samples prepared using different vulcanization conditions, while the role of filler was evaluated on composite samples containing different amounts of carbon black particles. 1H Multiple Quantum (MQ) experiments [4] were used for the measurement of the residual 1H-1H dipolar interaction, resulting from anisotropic fast fluctuations of chain segments, which depends on the amount and distribution of the topological constraints within the polymer network. Moreover, we investigated the effects of both the density of chemical cross-links and the presence of filler particles on the polymer chain dynamics in a wide spectrum of motional frequencies. This was possible by combining measurements of 1H spin-spin relaxation times (T2) [5] and variable temperature Fast Field Cycling (FFC) [6] experiments for the determination of 1H spin-lattice relaxation times (T1) as a function of the Larmor Frequency in the 10 kHz-35 MHz range. [1] Schlögl, S., Trutschel, M.-L., Chassé, W., Riess, G., Saalwächter, K. Macromolecules 2014, 47, 2759-2773 [2] Scotti, R.; D'Arienzo, M.; Di Credico, B.; Giannini, L.; Morazzoni, F. Silica-Polymer Interface and Mechanical Reinforcement in Rubber Nanocomposites. In Hybrid Organic-Inorganic Interfaces; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, Germany, 2017; pp. 151-198. [3] Kraus, G. Reinforcement of Elastomers; Interscience Publishers: New York, 1965. [4] Saalwächter, K. Prog. Nucl. Mag. Res. Sp. 2007, 51, 1-35. [5] Maus, A.; Hertlein, C.; Saalwächter, K. Macromol. Chem. Phys. 2006, 207, 1150-1158. [6] Kimmich, R. Field-cycling NMR Relaxometry: Instrumentation, Model Theories and Applications; The Royal Society of Chemistry, 2019.
Understanding the structural and dynamic properties of elastomeric materials by means of 1H time-domain nuclear magnetic resonance
F Martini;F Nardelli;M Geppi;L Calucci;S Borsacchi;E Carignani
2019
Abstract
Elastomeric materials are nowadays of central importance in many fields of application, where they need to fulfil specific mechanical requirements. The mechanical properties of an elastomeric material take their origin on the features and topology of the polymer network. In fact fixed chemical cross-links and physical entanglements among polymer chains impose notable restrictions on chain mobility and are at the basis of rubber elasticity [1]. Moreover, a significant reinforcement effect can be achieved by incorporation in the rubber matrix of different nanoparticles, such as carbon black, carbon nanotubes, nanosilica, and clays [2, 3]. Although in the past decades extensive research efforts have been addressed to the comprehension of the relationships between "molecular" and mechanical properties of elastomeric materials, a full understanding is still far from being achieved due to the complex interplay of many different factors. In this work we investigated the structural and dynamic properties of various elastomeric materials, based on isoprene, butadiene and styrene-butadiene rubbers, with application in the tyre industry, by combining different time-domain nuclear magnetic resonance (TD-NMR) techniques. The effect of cross-linking was explored by studying samples prepared using different vulcanization conditions, while the role of filler was evaluated on composite samples containing different amounts of carbon black particles. 1H Multiple Quantum (MQ) experiments [4] were used for the measurement of the residual 1H-1H dipolar interaction, resulting from anisotropic fast fluctuations of chain segments, which depends on the amount and distribution of the topological constraints within the polymer network. Moreover, we investigated the effects of both the density of chemical cross-links and the presence of filler particles on the polymer chain dynamics in a wide spectrum of motional frequencies. This was possible by combining measurements of 1H spin-spin relaxation times (T2) [5] and variable temperature Fast Field Cycling (FFC) [6] experiments for the determination of 1H spin-lattice relaxation times (T1) as a function of the Larmor Frequency in the 10 kHz-35 MHz range. [1] Schlögl, S., Trutschel, M.-L., Chassé, W., Riess, G., Saalwächter, K. Macromolecules 2014, 47, 2759-2773 [2] Scotti, R.; D'Arienzo, M.; Di Credico, B.; Giannini, L.; Morazzoni, F. Silica-Polymer Interface and Mechanical Reinforcement in Rubber Nanocomposites. In Hybrid Organic-Inorganic Interfaces; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, Germany, 2017; pp. 151-198. [3] Kraus, G. Reinforcement of Elastomers; Interscience Publishers: New York, 1965. [4] Saalwächter, K. Prog. Nucl. Mag. Res. Sp. 2007, 51, 1-35. [5] Maus, A.; Hertlein, C.; Saalwächter, K. Macromol. Chem. Phys. 2006, 207, 1150-1158. [6] Kimmich, R. Field-cycling NMR Relaxometry: Instrumentation, Model Theories and Applications; The Royal Society of Chemistry, 2019.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
