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PhD Thesis Defence Pilar Bernal Ortega on 13 March 2020

On Friday, March 13th 2020, Ms. Pilar Bernal Ortega will defend her PhD thesis entitled: 'Sulfur- modified carbon nanotubes for the development of rubber tire tread compounds'.

Location: Universidad Internacional Menéndez Pelayo (UIMP) in Spain.

Sulfur- modified carbon nanotubes for the development of rubber tire tread compounds

The unique properties of elastomers make them an ideal candidate for a wide range of applications, being tires the most important rubber products. The outer circumferential cover element of the tire, the tire tread, is in direct contact with the ground and hence suffers higher wear. Therefore, the properties of the tread are closely linked with the basic requirements of a good tire. The last years, the research on elastomeric materials in tire industry is focused on the rational development of new elastomer nanocomposites to be used in tire tread compounds.

The main aim of this thesis is to improve the durability and energetic efficiency of tires by applying the nanotechnology by the use of carbon nanotubes (CNT) and the exploration of new rubber reinforcing strategies. Additionally, a fundamental and systematic study has also been performed with the aim of quantifying the relative contribution of the different factors that determine the reinforcing effect of different nanoparticles in the rubber matrix.

In this work different natural rubber (NR) and styrene butadiene rubber (SBR) composites using carbon nanotubes (CNT) and surface-modified CNT as fillers were developed. This work will show that these promising materials could have some limitations to be applied in high-performance tire tread compounds (mainly related to the rolling resistance and fuel consumption) because of the difficulty of dispersion of CNT in rubber matrices (high filler networking), the strong influence of CNT in the vulcanization process (low cross-link density and high network defects) and the nature of rubber-filler interactions (high energy dissipations associated to the rupture of filler-rubber interactions at high strain amplitudes). However, the surface modification of the particles is a partial solution that overcomes this problems and leads to a reduction of the rolling resistance, to an increase in the cross-link density and the achievement of a more homogeneous network structure using a lower amount of filler volume fraction due to the most efficient use of sulfur during vulcanization.