Elastomers are polymeric materials widely used in the tyre industry. The peculiar properties of these materials, such as high viscosity and elasticity, are obtained through vulcanization in the presence of sulfur and other additives, including accelerators, activators and antireversion agents. In addition to curing agents, blends contain other additives, such as fillers and plasticizers, which are necessary to obtain specific mechanical requirements. Among them, resins are needed to improve tensile strength or fatigue resistance of the final products, as well as to facilitate the processing steps.[1] Generally, resins used in the tyre industry are based on petroleum-derived compounds, which are not sustainable and often carcinogenic. Environmental and health requirements impose the substitution of petroleum-based plasticizers with biocompatible and non-toxic alternatives in the production of elastomeric materials of interest for the tyre industry, while achieving comparable or even improved properties of the final products. To obtain this goal, it is important to understand the compatibility and miscibility between the new resins and the polymeric matrix at the molecular level,[2] which are strictly related to the macroscopic properties of the final products. For this type of study, it is possible to exploit Time Domain Nuclear Magnetic Resonance (TD-NMR) spectroscopy, which is particularly useful for investigating elastomers' dynamics and structure.[3] NMR observables, such as longitudinal and transversal relaxation times (T1 and T2) and 1H-1H residual dipolar couplings (Dres), depend on the modulation of the homonuclear dipolar interaction between protons mediated by molecular motions. As a result, these parameters allow phases with different mobility to be distinguished and the presence of topological constraints, such as cross-links and entanglements, to be highlighted. More specifically, T2 measurements allow to identify and quantify molecular environments with different mobility. From the analysis of T1, information about the mixing degree between different phases in multiphase systems can be achieved.[4] Other important information can be obtained from the average 1H-1H Dres which are directly proportional to the cross-link density.[5] Here, we studied styrene-butadiene rubbers vulcanized in the presence of natural origin or petroleum-based resins. Magic Sandwich Echo and Carr-Purcell-Meiboom-Gill experiments were acquired for the measurement of 1H T2 relaxation times to evaluate the molecular mobility of the polymeric and resin phases, also at different temperatures. Inversion Recovery experiments were performed to measure 1H T1 relaxation times in order to evaluate the homogeneity of the samples as a function of temperature. Moreover, Double-Quantum NMR experiments were acquired for the measurement of 1H-1H Dres to monitor the cross-link density in all vulcanized samples. References: [1] J. E. Mark, B. Erman, M. Roland, The Science and Technology of Rubber, (2013). [2] Indriasari, J. Noordermeer, W. Dierkes, Appl. Sci. 11, 9834, (2021). [3] K. Saalwächter, Rubber Chemistry and Technology, 85, 350, (2012). [4] K. Müller, M. Geppi, Solid State NMR: Principles, Methods, and Applications, (2021). [5] F. Nardelli, L. Calucci, E. Carignani, S. Borsacchi, M. Cettolin, M. Arimondi, L. Giannini, M. Geppi, F. Martini, Polymers, 14, 767, (2022).
Elastomeric Materials for Tyre Production Containing Resins of Natural Origin: A Time-Domain Solid-State NMR Study
L CALUCCI;
2022
Abstract
Elastomers are polymeric materials widely used in the tyre industry. The peculiar properties of these materials, such as high viscosity and elasticity, are obtained through vulcanization in the presence of sulfur and other additives, including accelerators, activators and antireversion agents. In addition to curing agents, blends contain other additives, such as fillers and plasticizers, which are necessary to obtain specific mechanical requirements. Among them, resins are needed to improve tensile strength or fatigue resistance of the final products, as well as to facilitate the processing steps.[1] Generally, resins used in the tyre industry are based on petroleum-derived compounds, which are not sustainable and often carcinogenic. Environmental and health requirements impose the substitution of petroleum-based plasticizers with biocompatible and non-toxic alternatives in the production of elastomeric materials of interest for the tyre industry, while achieving comparable or even improved properties of the final products. To obtain this goal, it is important to understand the compatibility and miscibility between the new resins and the polymeric matrix at the molecular level,[2] which are strictly related to the macroscopic properties of the final products. For this type of study, it is possible to exploit Time Domain Nuclear Magnetic Resonance (TD-NMR) spectroscopy, which is particularly useful for investigating elastomers' dynamics and structure.[3] NMR observables, such as longitudinal and transversal relaxation times (T1 and T2) and 1H-1H residual dipolar couplings (Dres), depend on the modulation of the homonuclear dipolar interaction between protons mediated by molecular motions. As a result, these parameters allow phases with different mobility to be distinguished and the presence of topological constraints, such as cross-links and entanglements, to be highlighted. More specifically, T2 measurements allow to identify and quantify molecular environments with different mobility. From the analysis of T1, information about the mixing degree between different phases in multiphase systems can be achieved.[4] Other important information can be obtained from the average 1H-1H Dres which are directly proportional to the cross-link density.[5] Here, we studied styrene-butadiene rubbers vulcanized in the presence of natural origin or petroleum-based resins. Magic Sandwich Echo and Carr-Purcell-Meiboom-Gill experiments were acquired for the measurement of 1H T2 relaxation times to evaluate the molecular mobility of the polymeric and resin phases, also at different temperatures. Inversion Recovery experiments were performed to measure 1H T1 relaxation times in order to evaluate the homogeneity of the samples as a function of temperature. Moreover, Double-Quantum NMR experiments were acquired for the measurement of 1H-1H Dres to monitor the cross-link density in all vulcanized samples. References: [1] J. E. Mark, B. Erman, M. Roland, The Science and Technology of Rubber, (2013). [2] Indriasari, J. Noordermeer, W. Dierkes, Appl. Sci. 11, 9834, (2021). [3] K. Saalwächter, Rubber Chemistry and Technology, 85, 350, (2012). [4] K. Müller, M. Geppi, Solid State NMR: Principles, Methods, and Applications, (2021). [5] F. Nardelli, L. Calucci, E. Carignani, S. Borsacchi, M. Cettolin, M. Arimondi, L. Giannini, M. Geppi, F. Martini, Polymers, 14, 767, (2022).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
