The effect of sulfate half-ester groups on the mechanical performance of cellulose nanocrystal-natural rubber composites

Abstract

Cellulose nanocrystals (CNCs) are commercially produced via hydrolysis by sulfuric acid, resulting in the formation of sulfate half-ester groups on the surface of the nanoparticles. The sulfate half-esters promote good colloidal stability but could affect other properties of the CNCs. To study the impact of the sulfate half-ester groups on the mechanical properties of CNC-natural rubber composites, sodium hydroxide was used as a desulfation agent to partially remove this chemical functionality. Mechanical characterizations revealed that CNCs conferred outstanding mechanical properties to the composites. At the same time, differences in the amounts of sulfate half-ester groups had remarkable consequences for the tensile strength and the dynamic mechanical properties, while the vulcanization properties of the composites were less influenced.

Cellulose Nanocrystals Show Anti-Adherent and Anti-Biofilm Properties against Oral Microorganisms

“…The presence of those groups on the CNC surface conferred the negative ζ-potential because sulfate half-esters are characterized by an extremely low pK a and are completely hydrolyzed as anions in neutral water (Figure 3b). The half-sulfate ester groups seem to play an essential role in determining CNC properties and when CNCs are processed for different applications [30][31][32][33][34][35].…”

“…On CNCs, unlike lignocellulosic raw materials, this band becomes narrower, longer, and more structured due to the high order of cellulose chain assembly. In fact, CNCs are also characterized by a high crystallinity index (>80%) where the diffraction pattern of cellulose I can be easily recognized [31]. The band at 2900 cm −1 indicates the C-H stretching vibration, while the small band at 1621 cm −1 indicates the presence of the C=O stretching vibration as well as the O-H bending vibration of absorbed water molecules.…”

“…Consequently, cellulose nanocrystals have received much attention due to their biocompatible and non-toxic properties, in addition to their promising antimicrobial properties. [14,15,[31][32][33]. It is interesting to highlight the bio-based nature of this nano-technological platform and the possibility of extracting CNCs from almost all the lignocellulosic biomasses available, even agro-industrial by-products, making them particularly promising from a circular economy point of view [36,37].…”