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An environmentally friendly procedure for the chemical modification of cellulose nanocrystals (CNCs), obtained from pine wood, was developed to manufacture hydrophobic CNCs. In comparison to other methods, this procedure has the particularity of producing a hydrophobic CNC in a single step, without using organic solvents while using MTMS as a precursor. CNCs were successfully dispersed in water, and the NMR technique was used to study the hydrolysis reaction of the MTMS in water before the surface modification of the CNCs. After 24 h of the modification reaction, the spray-drying method was used to produce a dry powder of modified CNCs. The obtained hydrophobic CNCs were characterized by several techniques. FTIR spectroscopy confirmed the covalent bonds between the MTMS and CNCs as well as the formation of nanostructured polymethylsilsesquioxane (PMSQ) on the surface of the CNCs. XPS spectroscopy examined the presence of Si atoms of the MTMS on the surface of the CNCs. XRD detected the presence of a crystalline structure of PMSQ on the surface of the CNCs and confirmed the preservation of the CNCs crystal after the modification operation. The morphology study using SEM, AFM, and TEM techniques confirmed the presence of nanostructured PMSQ on the surfaces of modified CNCs. The hydrophobic CNCs showed a significant increase in water contact angle (1108) compared to that of unmodified CNCs (438). This new way of modifying CNCs can produce hydrophobic CNCs with potential for dispersion in non-polar polymers for the formulation of new nanocomposites. Figure 15. (a) Thermogravimetric curves; and (b) DTG curves of CNC and CNC-1 % samples.

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Numerical modeling of the thermoforming process of polymeric sheets requires precise knowledge of the viscoelastic behavior under conjugate effect pressure and temperature. Using two different experiments, bubble inflation and dynamic mechanical testing on a high-density polyethylene (HDPE) nanocomposite reinforced with polymethylsilsesquioxane HDPE (PMSQ–HDPE) nanoparticles, material constants for Christensen’s model were determined by the least squares optimization. The viscoelastic identification relative to the inflation test seemed to be the most appropriate for the numerical study of thermoforming of a thin PMSQ–HDPE part. For this purpose, the finite element method was considered.

Unmanned aerial vehicles (UAVs) or drones are attracting increasing interest in the aviation industry, both for military and civilian applications. The materials used so far in the manufacture of UAVs are wood, plastic, aluminum and carbon fiber. In this regard, a new family of high-density polyethylene (HDPE) nanocomposites reinforced with polymethylsilsesquioxane nanoparticles (PMSQ), with mechanical performances significantly superior to those of pure HPDE, has been prepared by a fusion-combination process. Their viscoelastic properties were determined by oscillatory shear tests and their viscoelastic behavior characterized by the Lodge integral model. Then, the Lagrangian formulation and the membrane theory assumption were used in the explicit implementation of the dynamic finite element formulation. For the forming phase, we considered the thermodynamic approach to express the external work in terms of closed volume. In terms of von Mises stress distribution and thickness in the blade, the results indicate that HDPE-PMSQ behaves like virgin HDPE. Furthermore, its materials, for all intents and purposes, require the same amount of energy to form as HDPE.