Identifying Juncus plant as viable source for the production of micro- and nano-cellulose fibers: Application for PVA composite materials development

Abstract

With the aim of identifying new, renewable and sustainable sources for the production of bio-nano-materials, cellulose microfibers (CMF) and cellulose nanofibrils (CNF) were successfully produced from the widely available Juncus plant. CMF with average microfibers diameter of 3.5 μm were produced by conventional alkaline and bleaching treatments with a yield of around 36 %. CNF with average nanofibrils diameter of 2.5 nm were isolated from CMF by a combination of TEMPO-oxidation and mechanical disintegration processes. The morphology and physico-chemical properties of raw Juncus plant stems, CMF, TEMPO-oxidized CMF (T-CMF) and CNF were evaluated using several characterization techniques. It was found that the applied chemical treatments were effective in producing pure CMF and CNF materials having typical cellulose I structure, high crystallinity and good thermal stability. The as-extracted CNF were utilized to develop CNF-reinforced PVA nanocomposite films, and their transparency, thermal stability and mechanical properties were investigated and compared with the CMF and T-CMF reinforced PVA composite materials. It was found that the PVA nanocomposite material containing 5 wt% CNF exhibited a tensile modulus and strength of 3.3 GPa and 110 MPa, respectively, which are higher than those observed for neat PVA and PVA composites reinforced with 5 wt% CMF or T-CMF (modulus of 1.9 and 3.1 GPa and strength of 52 and 97 MPa, respectively). In contrast to CMF and T-CMF reinforced PVA composites, that displayed a reduced optical transmittance (ca. 57–70 % at 600 nm), the CNF-reinforced PVA nanocomposite material maintained the same transmittance of the neat PVA film (ca. 90 % at 600 nm), suggesting the good dispersion of CNF at the nanometric scale. These newly developed CNF could be considered as a potential nanofiller candidate for the preparation of PVA-based nanocomposite materials of high transparency and good mechanical properties.