Assessment of chemical and mechanical behavior of bamboo pulp and nanofibrillated cellulose exposed to alkaline environments

Abstract

This study was performed to study the effects of the cement paste composition (calcium aluminate cement-CAC-and a geopolymer in comparison to Portland cement-OPC-) on bamboo pulp and nanofibrillated cellulose (NFC). The changes in the composition and chemical structure of the fibers were analyzed by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). The changes in the mechanical strength were evaluated through tensile tests on the fibers after immersion on the cement pastes, in the form of sheets. The XPS results showed that the immersion of the pulp and NFC in the different pastes (CAC, geopolymer and OPC) modified the chemical surface of these fibers: it was found removal of lignin and extractives and some degradation of hemicellulose and cellulose. The FTIR analysis indicated modifications in the hydrogen bonds energy. The tensile strength of pulp sheets decreased in 70% and 34% after immersion in OPC and geopolymer, respectively. The tensile strength of the NFC sheets decreased 36%, 68% and 54% after immersion in OPC, CAC and geopolymer, respectively. Thus, the response of the bamboo pulp and NFC immersed in different cement pastes was different due the inherent characteristics of such fibers, and not only the Portland cement should be considered as harmful to lignocellulosic fibers. Although CAC and geopolymer are free of calcium hydroxide, the high alkalinity of these pastes also accelerated the degradation process of lignocellulosic fibers.

Surface Modification of Cured Inorganic Foams with Cationic Cellulose Nanocrystals and Their Use as Reactive Filter Media for Anionic Dye Removal

“…The cured geopolymer foams required further processing before they were brought together with CNCs because cellulose and cellulose nanoparticles are prone to degradation in alkaline conditions 47 and geopolymers are known to be highly alkaline due to residual NaOH remaining in the pore water after synthesis. 48 , 49 Consequently, there are four main sample types discussed in this section: Cured geopolymer foams (GP), acid-washed cured geopolymer foams (GP-AA), heat-treated cured geopolymer foams (GP-H), and heat-treated and acid-washed cured geopolymer foams (GP-H-AA).…”

“…One of the biggest obstacles hindering geopolymer surface modification with cellulose nanoparticles is the presence of free alkali in the material after geopolymerization, 48 , 49 which can trigger the degradation of the biopolymer if there is prolonged contact. 47 Therefore, extra effort must be made to effectively reduce the alkalinity of the geopolymer. In the case of geopolymer blocks, this has been achieved through excessive washing with water 11 , 22 or acids.…”

“…Cellulose , and natural cellulosic fibers (e.g., flax, bamboo, cotton) − have been used as a reinforcement agent in the geopolymer matrix due to their low densities, affordability, and good mechanical properties. However, the combination of cellulose nanoparticles with geopolymers has scarcely been studied, and indeed no information is available on the surface modification of geopolymers with cellulose nanoparticles. One of the biggest obstacles hindering geopolymer surface modification with cellulose nanoparticles is the presence of free alkali in the material after geopolymerization, , which can trigger the degradation of the biopolymer if there is prolonged contact .…”

“…However, the combination of cellulose nanoparticles with geopolymers has scarcely been studied, and indeed no information is available on the surface modification of geopolymers with cellulose nanoparticles. One of the biggest obstacles hindering geopolymer surface modification with cellulose nanoparticles is the presence of free alkali in the material after geopolymerization, , which can trigger the degradation of the biopolymer if there is prolonged contact . Therefore, extra effort must be made to effectively reduce the alkalinity of the geopolymer.…”

Geopolymers Reinforced with Natural Fibers: A Comparison among Different Sources

“…A further alternative is to insert renewable natural fibers of different origins [8][9][10][11]. Among these, flax has been frequently studied [12][13][14][15], as has bamboo [16][17][18][19]. Other types have received less attention, such as cotton [20,21], hemp [22,23] and kenaf.…”