Electron tomography provides a direct link between the Payne effect and the inter-particle spacing of rubber composites.

Rubber-filler composites are a key component in the manufacture of tyres. The filler provides mechanical reinforcement and additional wear resistance to the rubber, but it in turn introduces non-linear mechanical behaviour to the material which most likely arises from interactions between the filler particles, mediated by the rubber matrix. While various studies have been made on the bulk mechanical properties and of the filler network structure (both imaging and by simulations), there presently does not exist any work directly linking filler particle spacing and mechanical properties. Here we show that using STEM tomography, aided by a machine learning image analysis procedure, to measure silica particle spacings provides a direct link between the inter-particle spacing and the reduction in shear modulus as a function of strain (the Payne effect), measured using dynamic mechanical analysis. Simulations of filler network formation using attractive, repulsive and non-interacting potentials were processed using the same method and compared with the experimental data, with the net result being that an attractive inter-particle potential is the most accurate way of modelling styrene-butadiene rubber-silica composite formation.L.S. and P.A.M thank Michelin for funding. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement 291522-3DIMAGE.This is the final published version. It first appeared at http://www.nature.com/srep/2014/141209/srep07389/full/srep07389.html

Interplay between Polymer Chain Conformation and Nanoparticles Assembly in Model Industrial Silica/Rubber Nanocomposites

International audienceThe question of the influence of nanoparticles (NP) on chain dimensions in polymer nanocomposites(PNC) has been treated mainly through the fundamental way using theoretical or simulation tools andexperiments on well-defined model PNC. Here we present the first experimental study about theinfluence of NP on the polymer chain conformation for PNC designed to be as close as possible toindustrial systems employed in tire industry. PNC are silica nanoparticles dispersed into a Styrene-Butadiene-Rubber (SBR) matrix whose NP dispersion can be managed by NP loading with interfacialcoating or coupling additives usually employed in the manufacturing mixing process. We associatedspecific chain (d) labeling, and the so-called Zero Average Contrast (ZAC) method, with SANS, in-situSANS and SAXS/TEM experiments to extract the polymer chain scattering signal at rest for non-crosslinked and under stretching for cross-linked PNCs. NP loading, individual clusters or connectednetwork, as well as the influence of the type, the quantity of interfacial agent and the influence of theelongation rate have been evaluated on the chain conformation and on its related deformation. Weclearly distinguish the situations where the silica is perfectly matched from the unperfected matching bydirect comparison of SANS and SAXS structure factor. Whatever the silica matching situation, theadditive type and quantity and the filler content, there is no thus significant change in the polymerdimension for NP loading up to 15% v/v within a range of 5%. One can see an extra scatteringcontribution at low Q, as often encountered, enhanced for non-perfect silica matching but also visiblefor perfect filler matching. This contribution can be qualitatively attributed to specific h or d chainsadsorption onto the NP surface inside the NP cluster that modifying the average scattering neutroncontrast of the silica cluster. Under elongation, NP act as additional cross-linking junction preventingchain relaxation giving a deformation of the chain with NP closer to theoretical phantom networkprediction than for pure matrix

Thermal fatigue of anticorrosive coatings and multilayer coatings: a performance index approach

A strategy is proposed to cope with combined thermal fatigue and hot corrosion resistance affecting industrial coatings. It allows comparing different materials, coatings and geometries with respect to thermal cracking and then properly selecting protective coatings. It uses a thermo-mechanical model combining the heat transfer conditions, thermal and mechanical properties of the materials and the system geometry. The model is applied to two cases: (i) borided steel, with experimental support; (ii) multilayer coating made of a thermal barrier layer, aimed at reducing thermal gradients in the system, and a corrosion layer.info:eu-repo/semantics/publishe

Mechanism of aggregate formation in simplified industrial silica styrene–butadiene nanocomposites: effect of chain mass and grafting on rheology and structure

International audienceThe formation of aggregates in simplified industrial styrene–butadiene nanocomposites with silica filler hasbeen studied using a recent model based on a combination of electron microscopy, computer simulations,and small-angle X-ray scattering. The influence of the chain mass (40 to 280 kg/mol, PI < 1.1), which setsthe linear rheology of the samples, was investigated for a low (9.5 vol%) and high (19 vol%) silica volumefraction. 50% of the chains bear a single graftable end-group, and it is shown that the (chain-massdependent) grafting density is the structure-determining parameter. A model unifying all available dataon this system is proposed and used to determine a critical aggregate grafting density. The latter is foundto be closely related to the mushroom-to-brush transition of the grafted layer. To our best knowledge,this is the first comprehensive evidence for the control of the complex nanoparticle aggregate structurein nanocomposites of industrial relevance by the physical parameters of the grafted layer

An expert software for multi-layer coatings design in surface engineering

For the first time, a unique expert system able to give assistance to designers in surface engineering has been built. Not only is this software able to provide multi-layer coating solutions, but it is also able to rank different solutions according to their technico-economical interest. In addition to its ability to solve corrosion and wear concerns, it is also able to deal with surface finishing properties (like brightness, weldability, electrical conductivity, biocompatibility, …). This paper describes the structure of this expert system together with its main operation principles and future developments.info:eu-repo/semantics/publishe

Studying Twin Samples Provides Evidence for a Unique Structure-Determining Parameter in Simplifed Industrial Nanocomposites

The structure of styrene–butadiene (SB) nanocomposites filled with industrial silica has been analyzed using electron microscopy and small-angle X-ray scattering. The grafting density per unit silica surface ρ_<i>D</i>3 was varied by adding graftable SB molecules. By comparing the filler structures at fixed ρ_<i>D</i>3 (so-called “twins”), a surprising match of the microstructures was evidenced. Mechanical measurements show that ρ_<i>D</i>3 also sets the modulus: it is then possible to tune the terminal relaxation time of nanocomposites via the chain length while leaving the modulus and structure unchanged