Chemically modified natural fibers were introduced into a commercial biodegradable poly(butylene adipate-co-terephthalate) (PBAT) matrix to obtain composite materials in a mini-extruder. Influence of the fiber introduction on thermal and mechanical properties of the composites were studied. A decrease of the crystallinity degree of the composites was observed upon addition of the hydrolyzed-fibers, but the addition of the acetylated ones resulted in the opposite behavior. Thermal stability of the matrix was not affected by introduction of the treated fibers. However, an improvement of mechanical properties of the composites was found by means of dynamic mechanical thermal analysis and tensile tests, particularly for those containing acetylated fibers. Scanning electron micrographs of cryofractured surfaces of the composites showed stronger adhesion of the acetylated fibers to the PBAT matrix. No interfacial gaps or signs of the fiber pullout from the matrix were observed.

urauá (Ananas erectifolius) is a new lignocellulosic material possessing valuable properties. Scanning electron microscopy (SEM) studies of natural and delignified fibers reveal their dense structure and nanoveinlets of cellulose agglomerates. Thin Al 2 O 3 and Ta 2 O 5 coatings of various thicknesses (30 À 130 nm) are grown on the fiber surface by atomic layer deposition (ALD). Nanowalled microtubes of Al 2 O 3 and Ta 2 O 5 are prepared by annealing the coated fibers in an oxidative atmosphere to verify compactness, homogeneity, and continuity of the coatings obtained. The suitability of curauá fiber for ALD applications is shown. Both ALD coatings and the nanowalled microtubes replicate well the irregular fiber relief, they are resistant and homogeneous.

This study focuses on the methodology to obtain nanocellulose from vegetal fibers. An experimental planning was carried out for the treatment of curaua fibers and parameters were estimated, having the concentration of H 2 SO 4 , hydrolysis time, reaction temperature and time of applied sonication as independent variables for further statistical analysis. According to the estimated parameters, the statistically significant effects were determined for the process of obtaining nanocellulose. With the results obtained from the thermogravimetric analysis (TGA) it was observed that certain conditions led to cellulose with degradation temperatures near or even above that of the untreated cellulose fibers. The crystallinity index (I C ) obtained after fiber treatment (by X-ray diffraction technique) was higher than that of the pure fiber. Treatments with high acid concentrations led to higher IC. After the statistical experimental design, mixtures of polypropylene with fibers prepared after different treatments were performed in a mini-extruder. It was possible to observe a sharp increase in the mechanical properties through the dynamic mechanical thermal analysis (DMTA).

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Composites of polypropylene/natural fiber were obtained synthesizing polypropylene in the presence of chemically treated fibers. For this, vegetal cellulose fibers were introduced in the polymerization medium of propylene using Ziegler‐Natta catalyst. The fibers were treated to increase their compatibility with the polypropylene matrix and decrease the accessibility of functional groups to the catalyst active sites. At first, mild acid hydrolysis was performed, followed by chemical treatments with triethylaluminum and stearic alcohol. The results showed that the chemical treatments increased the crystallinity index to 73–77% in comparison with the original fiber (57.6%). The catalyst activity and its stereospecificity maintained high when fiber was treated with triethylaluminium and that with stearic alcohol. The composites contained amounts of fiber in a range of 3.1–5.8%. The fibers did not induce crystallization of PP crystallites different from the most common α‐form. Fibers were fibrillated to nanometric diameter, although micrometric length. POLYM. ENG. SCI., 56:71–78, 2016. © 2015 Society of Plastics Engineers