Abstract:We focused on preparing cellulose nanofibrils by purification, separation, and mechanical treatment of Kombucha membranes (KM) resulted as secondary product from beverage production by fermentation of tea broth with symbiotic culture of bacteria and yeast (SCOBY). We purified KM using two alkaline solutions, 1 and 4 M NaOH, which afterwards were subjected to various mechanical treatments. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS), X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) were employed to evaluate the purification degree, the size and aspect of cellulose fibrils after each treatment step, the physical-chemical properties of intermediary and final product, and for comparison with micro-crystalline cellulose from wooden sources. We determined that 1 M NaOH solution leads to approx. 85% purification, while a higher concentration assures almost 97% impurities removal. XRD analysis evidenced an increase in crystallinity from 37% to 87% after purification, the characteristic diffractograms of Iα and Iβ cellulose allomorphs, and a further decrease in crystallinity to 46% after microfluidization, fact correlated with a drastically decrease in fibrils' size. FTIR analysis evidenced the appearance of new chain ends by specific transmission bands at 2941 and 2843 cm −1 .

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Polymer composites with cellulose microfibrils are materials with unique properties compared to existing materials: high strength, formability, and geometrical complexity at very small scale, low density, and abrasivity, biomedical compatibility, and possibility of recycling. Polymer composites from polypropylene and two types of cellulose microfibrils were prepared and characterized. To enhance the compatibility of cellulose microfibrils with polypropylene matrix, a silane‐coupling agent and a modified polypropylene were used. Depending on the applied method, composite materials with enhanced mechanical properties were obtained. Morphostructural properties of cellulose microfibrils and polymer composites with treated and untreated microfibrils were investigated using scanning electronic microscopy (SEM), FTIR spectroscopy, and differential scanning calorimetry (DSC). POLYM. ENG. SCI., 47:1228–1234, 2007. © 2007 Society of Plastics Engineers

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Polymers filled with inorganic nanoparticles have become interesting materials as dielectrics because of their improved mechanical and electrical properties compared with the unfilled polymers and with polymer microcomposites. These improvements are mainly due to the large surface area of nanoparticles and new polymer-nanofiller interface characteristics. In the present work, polyethylene nanocomposites with SiO 2 and Al 2 O 3 nanoparticles were prepared by melt mixing. Mechanical and electrical properties of these composites were determined and morphological aspects were revealed by scanning electron microscopy, wide-angle X-ray diffraction, and atomic force microscopy. The effect of nanostructure and the importance of nanofiller dispersion were analyzed in connection with mechanical and electrical properties.

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