Efeito do tratamento mecânico por moinho de rolos nas propriedades de suspensão e de filmes à base de celulose microfibrilada

Abstract

Cellulose has been an alternative sought by industries and researchers to reduce the use of polluting products in production processes and reduce costs. Despite being the most abundant organic biopolymer on Earth, cellulose in some applications in its natural state may have limited use, as it is a heat-sensitive biotechnology in addition to being hygroscopic, which makes its processing difficult. Thus, the use of physical mechanical pre-treatments becomes an alternative to expand the use of this biopolymer in terms of homogenizing granules, reducing porosity and increasing yield to maximize production processes and, consequently, applicability. The shearing of fibers using a roller mill is characterized as a physical mechanical pre-treatment, as it provides compaction by the rollers, promoting an increase in the density, uniformity and tensile strength of the material, causing a reduction in porosity. This work aims to evaluate the efficiency of the effect of mechanical compaction and fibrillation treatment using a roller mill in the processing of microfibrillated cellulose (MFCs) from unbleached Eucalyptus pulp as a function of the number of cycles required in the equipment, making use of film characterizations and suspension, checking milling’s roller effect. Films were made from the suspensions and characterized sensorially (touch and smell); as well as analyzed by physical properties such as humidity, thickness, grammage, apparent density, porosity, water vapor permeability rate, wettability, contact angle; by morphological properties such as scanning electron microscopy; and mechanical tests such as tensile strength and modulus of elasticity. MFCs suspensions were characterized by their visual and structural aspects using light microscopy and scanning electron microscopy. From the results obtained after compaction and fibrillation by rollers, it is possible to verify that the mechanical pre-treatment resulted in changes that improved the characteristics of the MFCs, as the suspensions became more branched, homogeneous, with finer and more dispersed cellulose bundles. The pre-treated films, in turn, were thinner, more homogeneous, 11.16% less thick, 10.39% more dense, 14.98% more resistant to traction, 26.72% stiffer according to Young's modulus in addition to being 16.51% less porous.