Navegando por Autor "Tonoli, Gustavo Henrique Denzin"
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Item High moisture strength of cassava starch/polyvinyl alcohol-compatible blends for the packaging and agricultural sectors.(2015) Guimarães Júnior, Mário; Botaro, Vagner Roberto; Novack, Kátia Monteiro; Teixeira, Fábio Gomes; Tonoli, Gustavo Henrique DenzinThis study aimed to evaluate the thermal, mechanical, physical, structural and morphological properties of new polymeric mixtures based on cassava starch (CMS) and polyvinyl alcohol (PVA) in the proportions of 0/100, 20/80, 40/60, 50/50, 60/40, 80/20 and 100/0 using the casting method. The polymer concentrations and choice of plasticizer were defined after preliminary tests. Mechanical tests revealed that blends became more flexible and ductile with increasing the PVA proportion. The spectroscopy analysis showed significant alterations on the positions and intensity of the bands in 2920, 1415, 1150, 1077, 927 and 848 cm−1, thus indicating a good compatibility among the polymers. Increase of the CMS proportion was reduced until reaching 45%of the values of water vapor permeability (WVP) in relation to PVA biofilm. Any of the combinations was enough to make the blend less permeable than the CMS biofilm. After increasing the CMS proportions, all blends were more soluble in water compared to PVA biofilm. The exception was the 20P80A blend. Besides representing a tendency of higher opacity, all blends with elevated CMS proportions were more thermally stable when compared to those with the same proportions of PVA. Results showed the potential of such blends for applications on sectors of plastic and agricultural packages.Item Preparation of cellulose nanofibrils from bamboo pulp by mechanical defibrillation for their applications in biodegradable composites.(2015) Guimarães Júnior, Mário; Botaro, Vagner Roberto; Novack, Kátia Monteiro; Flauzino Neto, Wilson Pires; Mendes, Lourival Marin; Tonoli, Gustavo Henrique DenzinThere is a growing interest in cellulose nanofibrils from renewable sources for various industrial applications. However, there is a lack of information on cellulose arising from bamboo pulps. Nanofibrils from refined bamboo pulps, including bleached, unbleached, and unrefined/unbleached, were obtained by mechanical defibrillation for use in biodegradable composites. The influence of industrial processes, such as pulping and refining of unbleached pulps, as well as of alkali pretreatments and bleaching of refined pulps, on the chemical composition of the samples was analyzed. Morphological, structural, thermal, optical and viscometric properties were investigated as a function of the number of passages of refined/bleached suspensions through a defibrillator. For the unbleached suspensions, the effects of refining and bleaching on the properties of nanofibrils were evaluated, fixing the number of passages through the defibrillator. Microscopic studies demonstrated that nanoscale cellulose fibers were obtained from both pulps, with a higher yield for the refined/bleached and refined/unbleached pulp, at the expense of the unbleached/unrefined pulps. The study showed that, in addition to the effectiveness of the pre-treatments, there was an increase in the production efficiency of nanofibrils, as well as in the transparency of the bleached suspensions, while viscosity, thermal stability and crystallinity had reduced levels as the number of passages through the defibrillator increased, showing a gradual improvement in the transition from the micro- to the nano-scale. The present study contributed to the different methods that are available for the production of bamboo cellulose nanofibrils, which can be used in the production of biodegradable composites for various applications.Item Starch/PVA-based nanocomposites reinforced with bamboo nanofibrils.(2015) Guimarães Júnior, Mário; Botaro, Vagner Roberto; Novack, Kátia Monteiro; Teixeira, Fábio Gomes; Tonoli, Gustavo Henrique DenzinThis work aimed to evaluate the effect of including different concentrations of bamboo nanofibrils on physical, mechanical, morphological and structural properties of nanocomposites from cassava starch and polyvinyl alcohol (PVA). Nanocomposites were prepared with blends of starch/PVA and nanofibrils of bamboo. Chemical pre-treatments and mechanical defibrillation were used to obtain the nanofibrils. The mixture containing 3% of starch and 4% of PVA in the proportion of 20/80 (starch/PVA) were chosen after preliminary testing. Atomic force microscopy (AFM) and transmission electronic microscopy (TEM) were used to characterize the bamboo nanofibrils. Microstructure of the nanocomposites was evaluated using scanning electron microscopy (SEM) and X-ray diffractrometry (XRD). Physical and mechanical properties were also evaluated. Results showed that pre-chemical treatments increased the content of the alpha-cellulose in bleached pulp by approximately 112% in relation to the native fiber. Increasing the number of passages through the defibrillator reduced the average diameter of the bamboo nanofibrils (from 82±29nmto 10±6 nm). Addition of 6.5% nanofibrils improved the tensile strength and elongation at the break of the nanocomposite by 24 and 51%, respectively, but reduced the tensile modulus by 40% in relation to control (unreinforced) blend. Nanofibrils decreased the transparency of the nanocomposite films. The water vapor permeability and water solubility of the nanocomposite containing high contents of nanofibrils decreased up to 20% and 30%, respectively, in relation to the control blend.