In this work, the relationship between cellulose crystallinity, the influence of extractive content on lignocellulosic fiber degradation, the correlation between chemical composition and the physical properties of ten types of natural fibers were investigated by FTIR spectroscopy, X-ray diffraction and thermogravimetry techniques. The results showed that higher extractive contents associated with lower crystallinity and lower cellulose crystallite size can accelerate the degradation process and reduce the thermal stability of the lignocellulosic fibers studied. On the other hand, the thermal decomposition of natural fibers is shifted to higher temperatures with increasing the cellulose crystallinity and crystallite size. These results indicated that the cellulose crystallite size affects the thermal degradation temperature of natural fibers. This study showed that through the methods used, previous information about the structure and properties of lignocellulosic fibers can be obtained before use in composite formulations.

This work aims to evaluate the performance of glass/sisal hybrid composites focusing on mechanical (flexural and impact) and dynamic mechanical analyses (DMTA). Hybrid composites with different fiber loadings and different volume ratios between glass and sisal were studied. The effect of the fiber length has also been investigated. The densities of the composites were compared with the theoretical values, showing agreement with the rule of mixtures. The results obtained in the flexural and impact analysis revealed that, in general, the properties were always higher for higher overall reinforcement content. By DMTA, an increase in the storage and loss modulus was found, as well as a shift to higher values for higher glass loading and overall fiber volume. It was also noticed an increase in the efficiency of the filler and the calculated activation energy for the relaxation process in the glass transition region. The fiber length did not significantly change the results observed in all analyses carried out in this work. The calculated adhesion factor increased for higher glass loadings, meaning the equation may not be applied for the system studied and there are other factors, besides adhesion influencing energy dissipation of the composites.

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This study aims to evaluate the influence of fiber hybridization and frequency on the dynamic mechanical properties of ramie/glass hybrid fiber-reinforced polyester composites. The storage modulus (E 0 ), loss modulus (E 00 ) and damping behavior (tan d) were evaluated as a function of different relative glass/ramie fiber volume ratios. For the storage modulus, the importance of the reinforcement effect above T g was revealed. Also, the peak height, peak width at half-height and relaxation area were investigated for the loss modulus and tan d curves, showing the influence of a shoulder below T g for each case. Finally, the tan d peak shifts to higher temperatures by increasing the frequency. Higher activation energy was observed for 75% glass fiber-containing composites.

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Waterborne polyurethane coatings prepared by UV-induced photoreactions (UV-WPU) are becoming very attractive due to the increasingly stringent environmental demands. They were developed to replace solventbased polyurethanes in the coatings of wood, paper, plastics, metal, and glass, mainly because of their good physicochemical, rheological, and optical properties. Several UV-WPU formulations have been tested over the years, making their research substantial. However, no valuable review of this literature, focusing on the significant influencing factors in UV-WPU's manufacture, is available to date. This work aims to answer specific questions about the state of these materials' art, such as: "which monomers have been used most in UV-WPU synthesis?", "what type of photo-initiator has promoted the most efficient curing of the material?", "what additives or particles have been tested for composite UV-WPUs?", "which applications have UV-WPUs been directed to?", "what adaptations and technologies have already been tested to overcome the challenges of the process?", among others. As a result of a systematized bibliographic search in four databases, considering the period from January 2000 to July 2020, a total of one hundred and thirty-eight distinct and relevant articles on UV-WPUs were found. From this study, we hope to present a scientific source on the current state-of-the-art of UV-WPU synthesis, providing new combinations of raw materials and intelligent solutions, thus making material and industrial engineers able to mitigate the inconveniences of the process.