Natural Rubber Filled by Nan o silica: an ESR – Spin Probe Study

1. Natural Rubber Filled by Nanosilica: an ESR – Spin Probe Study • Lekić1, S.Valić1,2, A.P.Meera3 and S. Thomas3 • 1 University of Rijeka, School of Medicine, Braće Branchetta 20, Rijeka, 51000, Croatia • 2 Rudjer Bošković Institute, Bijenička 54, Zagreb,10000, Croatia • 3 Mahatma Gandhi University, School of Chemical Sciences, Kottayam, India - 686 560 Results Objective • Investigation of the NR samples containg different amounts of the nanosilica particles and their influence on local chain dynamics. • Influence of a coupling agent on the changes in matrix structure and chain dynamics. Materials Table 1. Samples of NR with different amounts of nanosilica Figure 2. ESR spectra of samples containing different amount of nanosilica measured at 10°C. Figure 1. ESR spectra of the spin probe diffusing in the matrix of Rub.ns00 sample at different temperatures. The average diametar of the used nanosilica particles was 13 nm. Table 2. NR samples with different amounts of coupling agent (Si 69) Figure 4. Temperature dependence of the outer extrema (2Azz) of ESR spectra for Rub.ns10 () and Rub.nscp04 (▲). Figure 3. ESR spectra of samples containing the same amount of nanosilica and various amounts of coupling agent measured at 10°C. Table 3. The intensities ratio of narrow and wide component of ESR spectra measured at 10°C. The amount of nanosilica in all samples containing the coupling agent was similar and equal 10 phr. Sample preparation • Two-roll mixing folowed by compression moulding. • Swelling in the toluene probe solution at the constant temperature (35°C). • Removing the solvent by evaporationand annealing at 60 C during tree days. a) without coupling agentb) with the coupling agent Figure 5.Schematic presentation of rubber matrices with the same crosslink densities and the same amount of the nanosilica. Methods Conclusion References ESR – spin probe method probe amount in the samples was 0.15 wt% ESR spectra show a significant influence of nanosilica on the local chain dynamics. The increase in the nanosilica amount leads to the decrease in segmental motions. The coupling agent makes the role of nanosilica more pronounced. Because of the better contact between the matrix chain segment and nanosilica particles, the restriction in local motions become more and more important as the amount of coupling agent increases. Z. Veksli, M Andreis, B. Rakvin, Prog Polym. Sci. 25 (2000) 949. G. Jeschke et al., Polymer Engineering and Science 44 (2004) 1112. 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl ESR spectrometar : Varian E-109 Temperature unit Bruker ER 4111 VT 17th European Symposium on Polymer Spectroscopy, September 9th to 12th, 2007 in Seggauberg, Austria