Alfa fibers as viable sustainable source for cellulose nanocrystals extraction: Application for improving the tensile properties of biopolymer nanocomposite films

Due to its renewability, availability and high cellulose content (≈45%), Alfa fibers (Stipa tenacissima) have been identified as a sustainable source for cellulose microfibers (CMF) and cellulose nanocrystals (CNC) production. Subjecting raw Alfa fibers to alkali, bleaching and sulfuric acid hydrolysis treatments allowed producing CMF and CNC with high yields. The fluorescence microscopy confirmed that CMF, with average diameter of 10 μm, were successfully obtained after bleaching treatments. TEM and AFM showed that the CNC exhibit needle-like shape with an average diameter and length of 5 ± 3 nm and 330 ± 30 nm, respectively, giving rise to an aspect ratio of about 66. XPS measurement confirmed the presence of sulfate groups on the surface of CNC with 2.04 sulfate groups per 100 anhydroglucose units, confirming the negatively charged surface of CNC, with zeta potential value of − 47.39 mV. XRD studies showed that CMF and CNC exhibit cellulose I structure with crystallinity index of 71% and 90%, respectively. FTIR and TGA analyses were used to identify the chemical composition and thermal stability changes during different chemical treatments, suggesting that all non-cellulosic compounds were removed after alkali and bleaching treatments. The obtained CNC were dispersed into three different biopolymer matrices, e.g. chitosan, alginate, and k-carrageenan, at various CNC loadings (1, 3, 5 and 8 wt%), to evaluate their ability to enhance the tensile properties of biopolymers and, at the same time, to produce new biopolymer-based nanocomposite films. It was found that the tensile properties of the as-produced nanocomposite films were largely improved with addition of CNC, resulting in mechanically strong and flexible ecofriendly nanocomposite films

Reuse of Red Algae Waste for the Production of Cellulose Nanocrystals and its Application in Polymer Nanocomposites

Red algae is widely available around the world and its exploitation for the production of agar products has become an important industry in recent years. The industrial processing of red algae generates a large quantity of solid fibrous wastes, which constitutes a source of serious environmental problems. In the present work, the utilization of red algae waste as raw material to produce high-quality cellulose nanocrystals (CNC) has been investigated, and the ability of the as-isolated CNC to reinforce polymer has been studied. Red algae waste was chemically treated via alkali, bleaching and acid hydrolysis treatments, in order to obtain pure cellulose microfibers and CNC. The raw waste and the as-extracted cellulosic materials were successively characterized at different stages of treatments using serval analysis techniques. It was found that needle-like shaped CNC were successfully isolated at nanometric scale with diameters and lengths ranged from 5.2 ± 2.9 to 9.1 ± 3.1 nm, and from 285.4 ± 36.5 to 315.7 ± 30.3 nm, respectively, and the crystallinity index ranged from 81 to 87%, depending on the hydrolysis time (30, 40 and 80 minutes). The as-extracted CNC were used as nanofillers for the production of polyvinyl alcohol (PVA)-based nanocomposite films with improved thermal and tensile properties, as well as optical transparency. It is shown that the addition of 8 wt % CNC into the PVA matrix increased the Young’s modulus by 215%, the tensile strength by 150%, and the toughness by 45%. Additionally, the nanocomposite films maintained the same transparency level of the neat PVA film (transmittance of ∼90% in the visible region), suggesting that the CNC were dispersed at the nanoscale

Effect of Fabric Layering Sequence and Architecture on Mechanical Properties of Clay, Jute, and Glass Fibers Reinforced Polyester Laminated Hybrid Composites

Hybrid laminated composites are attracting a lot of attention these days. Indeed, mixing natural and synthetic fabrics in the same matrix completely exploits the components’ greatest properties. However, it has been proven that the use of particles such as clays increases the material performance. Hence, the aim of this study is to produce a new hybrid laminated composite system using the hand lay-up method and compression molding techniques. For this, a layering sequence of plain-woven jute fabrics and different architecture of E-Glass fibers (matt and plain-woven roving fabrics with different grammage) were selected to strengthen a polyester resin modified with a tiny amount of clays. The effects of hybridization, layering sequence, and weaving architecture were evaluated by means of mechanical tests. The dispersion and distribution of the charges in the polymeric matrix were also investigated by studying the material rheological properties. We conclude that the proposed hybridization may result in an optimal, superior, and cost-effective laminated composite that fits all the requirements of a given structure