How the chemical nature of Brazilian hardwoods affects nanofibrillation of cellulose fibers and film optical quality

Abstract

A wide range of alternative cellulose fibers for the development of new green nanomaterials can be obtained from Brazil's natural resources. The objective of the work is to evaluate the influence of the chemical composition of hardwoods on the nanofibrillation process and optical quality of nanofiber films. Wood wastes were selected from three native Amazonian species and from exotic planted Eucalyptus grandis species. Wood sawdust was submitted to chemical alkali and bleaching pretreatments. Nanofibers were produced from the bleached fibers after 10, 20, 30 and 40 passes through a Super Mass Colloider grinder, and films were produced by the casting method. Raw sawdust, alkali-treated fibers and bleached fibers were evaluated by the major chemical components, syringyl/guaiacyl ratio, Fourier transformed infrared spectroscopy, oxygen/carbon ratio and scanning electron microscopy. Morphological characteristics of nanofibers and films were analyzed by transmission and scanning electron microscopies. Optical parameters studied for the films were the opacity, total color difference and b value. The main challenge to delignification was attributed to the low syringyl/guaiacyl ratio. The different chemical natures of Amazonian and eucalyptus hardwoods greatly affected pretreatments and, consequently, the nanofibrillation and optical quality of the films. Consequences observed for highly purified cellulose starting fibers are: (1) lower diameters for individual nanofiber elements; (2) fewer opaque and colored films produced from nanofibers; (3) a tendency to stabilization of the nanofibrillation process after 20 passes through the grinder. For species whose chemical nature hindered cellulose purification, the increased number L. Bufalino (of passes through the grinder continuously decreased the opacity.

Chitosan/Cellulose Nanofibril Nanocomposite and Its Effect on Quality of Coated Strawberries

“…at a working speed of 1,700 rpm and 5 A electric current, according to the methodology described by Bufalino et al [15] with same modifications. e nanofiber suspension obtained in the defibrillator was added to different chitosan concentration solutions after 24 h of stirring, and with the aid of an ultrasound, it was incorporated in different concentrations (3% and 5%) and then subjected to stirring for 1 h. e films were obtained by the same methodology as described by Guimarães et al [16,17].…”

Enhancement of the Amazonian Açaí Waste Fibers through Variations of Alkali Pretreatment Parameters

“…Composites based on cement, which is chemically incompatible with plant fibers, show better performance when a substantial amount of non‐cellulosic components is removed, including lignin . Other applications, such as the production of nanocellulose, require the removal of non‐cellulosic components in order to expose the cellulose microfibrils and reduce energy costs during nanofibrillation …”

“…Hemicelluloses are very soluble in low concentrations of alkali; hence easily removed by NaOH pretreatments. Alkali pretreatment also causes breakage of the fiber bundles into smaller fibers, which is attributed to partial lignin removal . Defibrillation is facilitated as the fiber wall structure is more open due to the dissolution of hemicelluloses and lignin .…”

Micro/Nanofibrilas Celulósicas De Eucalyptus Em Fibrocimentos Extrudados

“…As micro/nanofibrilas foram obtidas através de um desfibrilador mecânico (Super Masscolloider, Massuko Sangyo, modelo MKCA6-2) conforme sugerido por Guimarães Jr. et al (2015a) e Bufalino et al (2015).…”

“…O diâmetro médio das micro/nanofibrilas obtidas é de aproximadamente 50±4 nm. As dimensões destas micro/nanofibrilas são similares aos reportados para micro/nanofibrilas obtidas por sonificação (TONOLI et al, 2012b;CAMPOS et al, 2013) ou por desfibrilação mecânica (GUIMARÃES JR. et al, 2015a;BUFALINO et al, 2015) e estão na amplitude de tamanho que as fazem potencialmente úteis como agente de reforço em compósitos cimentícios. Entretanto é importante observar que há uma pequena fração de fibras que não foram completamente desconstruídas, o que acentua a importância da otimização dos tratamentos para obter melhores rendimentos de micro/nanofibrilas.…”