HIGH AND LOW RESOLUTION SSNMR STUDY OF SEPIOLITE/NATURAL RUBBER COMPOSITES PREPARED BY LATEX COMPOUNDING

Mechanical properties of rubber-based materials critically depend on addition of reinforcing llers. Among other factors, the shape of ller particles aects the nal properties and, in particular, clays can impart a larger reinforcing eect than spherical particles. Sepiolite (Sep), a natural Mg phyllosilicate, has attracted attention for its easy availability, high specic surface area, strong mechanical and chemical stability, and ber shape. Natural rubber latex (NRL), a colloid mainly composed by poly(1,4-cis-polyisoprene) and water, can be exploited to prepare rubber nanocomposites through the latex compounding technique (LCT), which represents an ecosustainable alternative to the well-established melt mixing technique [1]. Very recently an eective LCT procedure to produce high-loaded Sep/NR masterbatches was repoted by some of us [2]. These materials are interesting in the research for ecosustainable composites production, but it is known that metal ions, present as impurities in clays, can promote oxidation and thermo-degradation of the rubber matrix, which can also be favoured by the presence of water as solvent [3,4].The issue of controlling oxidative reactions and develop procedures able to avoid oxidation is therefore relevant. In this context, the present work exploits a combination of high and low resolution solid state NMR experiments, with the support of DSC and FT-IR, applied to a set of Sep/NR masterbatches prepared by LTC, with the aim of investigating the eect of the Sep treatment and of the work-up procedure on the stability and dynamics of NR. In particular, 1H and 13C selective MAS experiments and 1H time domain experiments (MSE and CPMG sequences) were carried out on masterbatches prepared with dierent types of Sepiolite - either pristine or organically modied, and subjected or not to specic acid treatmens - with the aim of understanding the eect of the sepiolite treatments on oxidation, and the relation between the oxidative processes and the dynamic properties of the rubber. References: [1] J. W. Lightsey, D.J. Kneiling, J.M. Long, Rubber World 218, 35-40, (1998). [2] B. Di Credico, et al. Nanomaterials 9, 46, (2019). [3] M. Chen, N-J. Ao, Y. Y. Liao, Y. Chen, H.L. Zhou, J. Appl. Polym. Sci. 100, 3809, (2006). [4] M. Chen, et al. J. Appl. Polym. Sci. 82, 338, (2001).