Isolation of cellulose nanofibers from para rubberwood and their reinforcing effect in poly(vinyl alcohol) composites

Abstract

In this article, we present an efficient method for isolating cellulose nanofibers from para rubberwood sawdust with a combination of chemical, mechanical, and ultrasonic treatments. The effects of the alkali concentration and treatment pathway on the cellulose structure and properties are discussed. The reinforcing efficiency of the resulting fibers on poly(vinyl alcohol) (PVA) composites was characterized. Field emission scanning electron microscopy and atomic force microscopy results revealed a well-organized network of the nanofibers with diameters in the range 20-80 nm and lengths of micrometer-scale dimensions. Fibers with a high crystallinity of 83% having a cellulose I structure were prepared by an isolation process involving a mild alkali solution and delignification before acid hydrolysis. Clear composite films with significant improvements in their modulus (by 100%) and strength (by 80%) were obtained by the addition of 7 wt % fiber. Strong interaction between the fibers and PVA was evident from dynamic mechanical analysis and differential scanning calorimetry.

Cellulose nanocrystals extracted from okra fibers in PVA nanocomposites

“…The strong band at 1245 cm À1 is assigned to the ester acetate CAO bending mode and other peaks located at 1413 cm À1 , assigned to the symmetric (ms.) stretching vibration of the ACOOA group, and 1092 cm À1 , due to CAO stretching can be found related to PVA 51,52. A broad band observed from 3200 to 3550 cm À1 in the PVA spectra corresponding to the hydroxyls (AOH) stretching due to the strong hydrogen bond of intramolecular and intermolecular type, which indicate the presence of hydroxyl groups.…”

Structural and mechanical properties of cellulose composites made of isolated cellulose nanofibers and poly(vinyl alcohol)

“…The reported 10 wt% cellulose nanofiber/PVA composite presented an increase in Young's modulus from 45 MPa to 120 MPa [10]. Thus, it was confirmed that the cellulose nanofibers were promising materials for the reinforcement of polymers, and continuous and enormous efforts have been made to isolate cellulose nanofibers.…”

“…PVA powder was dissolved in distilled water and stirred at 95°C for 3 hours to produce 5 wt% PVA solution [10] with high transparency. Cel-F suspension was then mixed to the 5 wt% PVA solution and stirred for 1 hour.…”

“…Therefore, the pulverization process of the cellulose normally needed multiple steps, in which toxic solvents or detrimental catalysts (e.g. strong acid, chlorine dioxide (ClO 2 ), and acidified sodium chlorite (NaClO 2 )) were used [10][11][12][13]. However, in order to maintain and utilize the good biocompatibility of cellulose, a simple isolation scheme of cellulose nanofibers without using damaging substances has been increasingly required.…”

The Structure and the Mechanical Properties of a Newly Fabricated Cellulose-Nanofiber/Polyvinyl-Alcohol Composite

“…It is, however, known to be quite challenging to extract cellulose nanofibers from original cellulose beads because of the strong interfacial interactions functioning between cellulose molecular chains due to hydrogen bondings. Therefore, nanofabrication processes of cellulose generally have multiple processing steps which occasionally required the use of toxic solvents or catalysts [1][2][3][4].…”