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Award for characterizing mechanical and chemical interactions

Samet Varol has been awarded with the Gold prize in the "Young Scientist Lecture Competition Award" for his lecture about the relation between chemical and mechanical properties of nanocomposites at NANOSMAT conference (19.-22. May 2014), which took place at Rice University in Houston, Texas (USA).

As a PhD student at Max Planck Institute for Polymer Research (MPIP), Varol investigates the fundamental determinants of rheological properties, in other words the deformation behavior, of nanocomposites. Nanocomposites are blended materials that contain nanoscale hard fillers in a polymer matrix, which can appreciably alter the mechanics and functionality compared to the carrier polymer alone.

Varol wants to understand the relation between mechanical properties and molecular interactions of the nanocomposites that give rise to unique mechanical properties. He presented his current results in the awarded lecture. Two very similar silica/rubber nanocomposite structures , one designed for car tyres and the other as a basic material for sealants, were uniaxially deformed while vibrational spectroscopic data were simultaneously obtained. Varol analyzed the spectroscopic data from the different material formulations, and combined these results with his previous work characterizing the morphological differences of the nanofillers in the polymer matrices, to arrive at a model for the nonlinear elasticity in the composite materials.

A well-known nonlinear property of nanocomposites is the Payne effect, which can be generally described as strain-softening of an elastomer material. According to Varol's insights, the size of the primary nanoparticles - and thereby their ultimate morphology in the composite - is an essential determinant of the Payne effect. The bigger the particles, the smaller the Payne effect.

Varol's next challenge will be to unravel how changes in polymer-filler chemistry influence this and other mechanical behaviors of these materials (e.g. Mullins effect). Together with his project leader, Sapun Parekh, they plan to augment their studies by using advanced spectroscopies in the Molecular Spectroscopy Department to obtain a more detailed chemical picture of the matrix-filler interaction. Their ultimate goal of their research is to provide a molecular picture to explain the mechanical behavioral differences of nanocomposites that can be used to rationally design and optimize composites for specific purposes. This work is part of an international industrial and academic partnership between SKF, Michelin, the University of Amsterdam, and the MPIP.

Source: Max Planck Institute for Polymer Research (MPI-P)