ABSTRACT In this study, based on the mechanical shear treatment, the cellulosic pulp was fibrillated in nanofibrils dispersed in aqueous suspension. Nanofibrillated Cellulose (NFC) matrix - Polyvinyl Alcohol (PVA) nanocomposite films’ were prepared by casting from NFC/PVA suspension mixtures. The thermal and mechanical properties of the obtained films were evaluated. Low levels (2, 5 and 10 wt%) of PVA were used as an additive in a nanofibrillated cellulose (NFC) matrix. The predominant use of NFC, with superior properties due to its purity, with an efficient and environmentally friendly method, has allowed the production of NFC-based biodegradable materials with enhanced properties for high-level applications. The addition of PVA to the NFC matrix produced positive results, as it causes little aesthetic interference, without changes in surface brightness. After the addition of PVA the films showed a great gain in mechanical strength, increasing by 24% in Young’s modulus with the addition of 10% PVA. Even after addition, the samples’ chemical composition remains unchanged and the mixture shows a decrease in the film surface hydrophilicity when compared to pure NFC. Composite material thermal analysis indicates that thermal degradation temperatures remain unchanged after the addition of PVA. Although PVA is not very temperature resistant, in the proportions used, NFC thermal resistance is preserved.

ABSTRACT The basic density is the main technical property of the wood due to the fact of the easy determination and correlation with the others wood properties. In this article, it was evaluated wood chips from a five-years-old Eucalyptus grandis in three different silvicultural treatments for pulp and paper production. First, a conventional kraft pulping was executed in the same conditions and then submitted to some elemental chlorine free (ECF) bleaching process to achieve the target brightness of 88 ± 1% ISO. The bleached pulps were refined in a Jokro Mill at 0, 2250, 4500 and 6750 revolutions and their physical, mechanical and optical properties were analyzed. The statistical analysis indicated a difference in the wood basic density from the different silvicultural treatments. The yield of the pulping process was not affected by the variation of the wood basic density. The denser wood had the advantage of a lower specific wood consumption while the disadvantage was a greater difficulty in the delignification and a decrease in the selectivity of the pulping process. The denser wood was the one with the best bleachability and the one that most consumed chlorine in the bleaching process. The increase of the wood density caused gains in the fisical and optical properties of the bleached pulp and losses in the mechanical properties.The optical properties of the pulps from denser woods are more resistant than the negative effects of mechanical properties.

ABSTRACT In this work, we studied the infl uence on the mechanical and physical properties of paper made of pulp from recycled cardboard and paper (printing/writing and newsprint) by adding different percentages of nanofi brillated cellulose. For each type of recycled pulp, we formed paper with incorporation of 0, 5 and 10 wt% nanofi brillated cellulose. The results showed that addition of nanofi brillated cellulose reduced the paper thickness and increased the density values. Papers with nanofi brillated cellulose presented resistance properties with values statistically superior to the treatments without addition. Addition of 10 % provided the best results, with improvement of tensile, burst and tear resistance of 97, 133 and 104 %, respectively, in comparison to normal papers. The paper produced with the recycled newspaper pulp had lower increase in mechanical properties from the nanofi brillated cellulose in relation to the papers with recycled pulp from cardboard and printing and writing paper. The considerable improvement in the mechanical properties is related to the increase of hydrogen bonds between the fi bers and nanofi bers, forming a dense network, resulting in greater surface area of nanofi brillated cellulose.