Nanowear in a nanocomposite reinforced polymer

We investigated the reinforcement of blends made from poly(ethyl methacrylate) (PEMA) and PEMA-grafted nanoparticles at a nanometer length scale. The reinforcement was probed by nanowear experiments based on scanning force microscopy (SFM). In addition to imaging, the SFM is applied to wear the surface of samples at the length scale of nanoparticles. Blends with different miscibility of nanoparticles were prepared by varying the molecular weights of polymer grafted from the nanoparticles (N) and polymer forming the matrix (P). We were able to associate a critical force for the onset of nanowear by analyzing the nanowear patterns resulting from different normal loads during the nanowear experiment. The definition of this critical force allows quantitative comparison of nanoparticle-polymer systems of different composition. Nanowear tests indicated that only mixtures where N/P > 1 reinforced the composite material compared to the pure homopolymer. Under these conditions the grafted polymers were swollen and the nanoparticles acted as additional anchor sites. As reference experiments we used a blend made from PEMA homopolymer and unmodified particles. Non-grafted nanoparticles clearly did not account for any reinforcement.

SFM topography image after a nanowear test on a nanocomposite sample composed of polymer grafted nanoparticles and hompolymers.Figure optionsDownload high-quality image (205 K)Download as PowerPoint slideHighlights
► The wear of nanocomposites was studied on a nanometer scale.
► The onset of nanowear is characterized by a critical normal force.
► We investigate nanowear of nanocomposites made of modified nanoparticles and polymers.
► Polymer grafted nanoparticles are reinforcing low Mw polymers.
► Unmodified nanoparticles clearly did not account for any reinforcement.