Browsing by Author "Novoa Herrera, Fernanda Camila"

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    Compuestos de caucho reforzados con celulosa nanofibrilada.
    (Universidad de Concepción, 2023) Novoa Herrera, Fernanda Camila; Pereira Soto, Miguel A.; Castaño Rivera, Patricia; Soto Arriagada, Alexandra
    In the rubber industry, carbon black and silica are the most used reinforcing agents; however, their production processes consume large amounts of energy and are not environmentally friendly. From this problem, the need arises to look for new reinforcing agents that have characteristics such as biodegradability, easy availability and with a production process that does not generate a significant deterioration for the environment, being the nanocellulose and in particular, the nanofibrillated cellulose, a striking alternative as a replacement for conventional reinforcing agents. Based on the above, the objective of this research was to study the effect of nanofibrillated cellulose as a reinforcing agent in natural rubber compounds and their physical-mechanical properties, evaluating the effect of the degree of fibrillation of nanofibrillated cellulose, as well as the effect of the concentration of nanofibrillated cellulose in the rubber compounds, to finally compare the results obtained with compounds formulated from conventional reinforcing agents. For this purpose, nanofibrillated cellulose was prepared by means of a mechanical-enzymatic treatment from bleached Eucalyptus kraft pulp, from which cellulose nanofibers of different degrees of refinement were obtained with 0, 4 and 12 passes through a homogenizer. On the other hand, all composites of nanofibrillated cellulose with natural rubber were prepared by mixing in solution and coagulates of the nanocomposites were obtained by coagulation with acetic acid. For the characterization of the composites, their rheometric properties, physical properties, abrasion tests, tensile-elongation tests, Fourier transform infrared spectroscopy (FTIR) analysis, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were obtained. For the effect of the degree of fibrillation of nanofibrillated cellulose in rubber composites, better results in physico-mechanical properties were obtained for the composite with unrefined nanofibers, translating into an advantage from an energetic, economic and processability point of view. In particular, the nanocomposite with the less refined nanofiber achieved improved peak torque at 33.5%, hardness at 23.4%, modulus at 300% at 93.2%, compared to an unreinforced natural rubber composite. In general, the results were not significantly better for the composites with the nanofibers of higher degree of refinement, due to a non-optimal dispersion resulting from the greater interaction between the nanofibers, over the interaction between the nanofibers and the rubber matrix, generating possible agglomerates and concluding that it is not necessary to refine the cellulose nanofibers. For the effect of concentration, compounds were prepared with 5, 10, 15 and 30 phr of unrefined nanofibrillated cellulose, only up to 15 phr increased the reinforcing effect, since the higher the concentration, the properties decreased due to the agglomeration of the fibers in the rubber matrix. In particular, the compounds with 10 and 15 phr showed better results. For the compound with 10 phr the maximum torque increased by 43.1% and for the hardness by 34.4% with respect to the unreinforced compound. While the compound with 15 phr increased the tensile strength by 37.6% and the modulus at 300% to 154.7% with respect to the unreinforced natural rubber compound. Finally, the composites with 10 and 15 phr of nanofibrillated cellulose were compared with composites with 30 phr of silica and 30 phr of carbon black. Only in the loss of volume due to abrasion did the use of nanocellulose not show favorable results, which poses the challenge of improving its results in future studies, through better nanofiber-rubber compatibility. While for the other physico-mechanical properties compared, similar values were obtained to those of conventional reinforcing agents and even better in the nanocomposites, making nanofibrillated cellulose a promising and innovative reinforcing agent for natural rubber composites.
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