Study of the Properties of Rubber-Resin Compounds by Solid-State NMR: Effect of The Type of Resin

Elastomers, produced by vulcanizing polydiene polymers with sulfur and other additives, areextensively used in the tire industry. Resins are often incorporated to enhance the tensile strength,fatigue resistance, and processing of elastomeric products.[1] However, the petroleum-based resinsused in the industry are unsustainable and possibly cancer-causing. To address environmental andhealth issues, biocompatible, non-toxic alternatives, that maintain or enhance the fi nal product'sproperties, are necessary.[2] Understanding the molecular compatibility and miscibility between newresins and the polymer matrix is crucial, as these factors affect the overall properties of the products. Here, ¹H time-domain (TD-NMR) and high-resolution solid-state NMR (SS-NMR) techniques wereapplied to investigate the dynamics and structural properties of uncured and cured compounds ofstyrene-butadiene-rubber (SBR) containing three different tackifying resins, two derived frompetroleum and one derivative of colophony pine resin. The structural and phase properties of thecompounds were investigated by the analysis of ¹³C SS-NMR spectra and the measure of ¹H T?relaxation times. Information on the degree of mixing between the resin and SBR components wereobtained by ¹H T? and T?? measurements. Field-cycling NMR relaxometry was used to measure ¹H T?relaxation times over a wide range of ¹H Larmor frequencies and at different temperatures, allowing toinvestigate dynamics over a wide range of motion time scales. The obtained NMR data were comparedwith crosslink density and macroscopic properties, which are routinely analysed in industrial settings tounderstand the effects of formulation and vulcanization conditions on the structure and dynamics ofpolymer networks.[3] References [1] Indriasari, J. Noordermeer and W. Dierkes Appl. Sci. 11, 9834 (2021) [2] J. Thomas and R. Patil Environmental Science & Technology 57 (6), 2209 (2023) [3] M. Pierigé, F. Nerli, F. Nardelli, L. Calucci, M. Cettolin, L. Giannini, M. Geppi, and F. Martini Appl. Sci.13, 1939 (2023)