AFM PeakForce QNM mode: Evidencing nanometre-scale mechanical properties of chitin-silica hybrid nanocomposites.

PeakForce Quantitative Nanomechanical Mapping (QNM) AFM mode was used to explore the mechanical properties of textured chitin-silica hybrid films at the nanoscale. The influence of the force applied by the tip on the sample surface was studied for standard homogeneous samples, for chitin nanorods and for chitin-silica hybrid nanocomposites. Thick films of superimposed chitin nanorods showed a monotonous increase of DMT modulus (based on the Derjaguin-Muller-Toporov model) owing to an increase in modulus at the interface between nanorods due to geometrical constraints of the AFM acquisition. A similar variation of DMT modulus was obtained for chitin-silica hybrid thick films related to mechanical strengthening induced by the presence of silica. This work revealed the role of the organic-inorganic interface, at the nanoscale, in the mechanical behaviour of textured materials using PeakForce QNM mode, with optimized analysis conditions.

Use of new synthetic talc as reinforcing nanofillers for polypropylene and polyamide 6 systems: thermal and mechanical properties.

New layered synthetic nanotalc prepared at a lab-scale by a conventional hydrothermal process and commercial natural fine talc were used in order to establish a comparative study in terms of their contributions on the improvement of the final properties of two different polymers: a nonpolar polyolefin matrix and a polyamide. All samples were prepared by melt extrusion in a co-rotating microcompounder. The surface properties of talc - surface energy and isoelectric point - were probed. The particles' crystalline structure and the distribution/dispersion within the polymer matrix were performed using transmission electron microscopy and X-ray diffraction. The effect of talc particles on the crystallinity, the thermal and mechanical properties was highlighted as a function of the surface properties of talc. In the case of talc-filled PP systems, it seems that the incorporation of both natural and synthetic talc greatly improves the thermal stability of polypropylene matrix. The highest elastic modulus was obtained in presence of highly nucleating natural talc. Oppositely, the best ductility was observed for the synthetic talc-filled PP systems. For PA6/talc nanocomposites, a remarkable improvement in the dispersion of talc layers was shown and a significant increase in Young's modulus was determined due to the closer affinity between the hydrophilic nanotalc lamellae and the polar PA6 matrix.