Effects of nanocellulose formulation on physicomechanical properties of Aquazol–nanocellulose composites

Abstract

Aquazol [poly(2-ethyl-2-oxazoline)] is a widely used polymeric material for conservation because of its high reversibility and excellent compatibility with various types of material. However, it is hydrophilic and not recommended for use in weight-bearing applications. The objective of this study is to introduce cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) into Aquazol to evaluate the physicomechanical properties of the resultant composites. Several nanocellulose addition formulations involving two types of nanocellulose were designed at various addition levels. Water sorption investigations revealed that the addition of CNCs or CNFs reduced the maximum moisture content of the resultant composites when compared to the unfilled Aquazol. The tensile test results showed that the critical addition level of CNF (2 wt%) is lower than that of CNC (10 wt%) for the nanocellulose to start acting effectively as a mechanically reinforcing agent. Notably, compared with using a single type of nanocellulose for reinforcement, greater reinforcement was observed when both CNCs and CNFs were combinedly added. Field emission scanning electron microscopy indicated that these strong reinforcement outcomes were probably a result of branch-like structures forming among the mixed fillers. The addition of nanocellulose in general resulted in composites having marginally lower thermal stability and optical transparency. In this study, we demonstrated the increased retention of mechanical properties in variously filled composites exposed to anticipated service conditions (55% RH; 23 °C). Crucially, the discoveries in this study indicate that mixed CNC and CNF fillers could be a reasonable option for future applications where lower levels of nanocellulose are desired for optical transparency considerations.