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Boehmite is an aluminum oxyhydroxide [AlO(OH)] which is preferentially used as precursor for the production of (transition) aluminum oxides. Boehmite alumina (BA) nanoparticles are available in various morphologies due to versatile synthesis routes, which are briefly introduced. The peripheral hydroxyl groups of BA offer manifold functionalization possibilities for tailoring the dispersion and filler/matrix adhesion properties. The incorporation of BA nanofillers, with and without surface treatments, may yield improved mechanical and novel functional properties in polymers. BA can be introduced in polymers and polymer composites through different methods. This comprehensive overview covers the basic results reported on polymer/BA nanocomposites in the open literature. In this review, polymer matrices are grouped into thermoplastics, thermosets, and rubbers. Using literature results and our own findings, we have identified promising R&D trends with polymer/BA nanocomposites. V C 2017 Wiley Periodicals, Inc. J.Appl. Polym. Sci. 2018, 135, 45573.

Water-assisted, or more generally liquid-mediated, melt compounding of nanocomposites is basically a combination of solution-assisted and traditional melt mixing methods. It is an emerging technique to overcome several disadvantages of the above two. Water or aqueous liquids with additives, do not work merely as temporary carrier materials of suitable nanofillers. During batchwise and continuous compounding, these liquids are fully or partly evaporated. In the latter case, the residual liquid is working as a plasticizer. This processing technique contributes to a better dispersion of the nanofillers and affects markedly the morphology and properties of the resulting nanocomposites. A survey is given below on the present praxis and possible future developments of water-assisted melt mixing techniques for the production of thermoplastic nanocomposites.

In this study thermoplastic starch (TPS) matrix-based microfibrillated cellulose (MFC) reinforced microcomposites were prepared via extrusion compounding in one-step. Starch was plasticized with a combination of glycerol and water. The native starch/glycerol and the plasticized starch/water ratios were set for 4/1 and 6/1, respectively. Two different MFC types (of varying mean length and diameter) were incorporated up to 20 wt.% in the plasticizer-containing premix prior to its compounding in a twinscrew extruder. The mechanical properties of the TPS biocomposites were markedly enhanced by the introduction of MFC. The yield strength was improved by ~50%, whereas the stiffness by ~250% upon adding 20 wt.% MFC compared to the parent TPS. Dynamic mechanical analysis (DMA) revealed that the reinforcing effect of the MFC was more prominent in the starch-than in the glycerol (plasticizer)-rich phase of the TPS. The mean length and diameter of the MFCs, yielding similar aspect ratio values lying below the estimated critical one, influenced the mechanical, thermal and thermo-mechanical properties marginally.

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