Flaxseed plants are widely grown globally due to the beneficial seed oil derivatives for human and animal consumption and other industrial uses. However, plentiful flaxseed straws are annually burnt after the harvesting of seeds, lacking utilization of the abundant flaxseed fibers, resulting in wastage of a valuable fiber resource and drastic increase in environmental pollution. In this study, initially the chemical composition and mechanical property of flaxseed fiber bundle were investigated, which resulted as 40.11% cellulose, 28.27% hemi-cellulose, 15.08% lignin, 6.3% pectin, 3.1% wax, and the tensile strength of 1.14 cN/dTex. The surface modification treatment was carried out with concentrations of 10 g/L and 20 g/L sodium hydroxide (NaOH). Later, flaxseed fiber bundles reinforced Polybutylene Succinate (PBS) resin composites were fabricated by thermal compression method. The tensile strength of untreated flaxseed fiber bundle/PBS composites was 78.2 MPa, while the flexural strength of 20 g/L NaOH treated flaxseed fiber bundle/PBS composites showed 84% increment from 26.70 MPa to 49.16 MPa. The scanning electron microscopy (SEM) images revealed significantly rougher surface morphology and stronger interfacial bonding of the alkali treated fiber bundles with matrix. The good mechanical properties observed demonstrated the absolute potential of resultant composites reinforced by flaxseed fiber bundles for utilization in the civil and industrial applications.

In this study, discarded denim fabric was adopted to enhance the mechanical and thermal properties of polypropylene (PP). The composites with different fiber weight fractions were designed and fabricated by using a hand layup and hot pressing method. The tensile, impact, and flame-retardant properties of the composites were investigated and their morphology was observed by scanning electron microscopy. Owing to the integrity structure and good mechanical property of denim fabric, the tensile strength and impact strength of the 84 wt% denim-reinforced composite were up to 57 MPa and 5.1 J/mm, which super exceed those of the ramie/PP composites (26 MPa) and flax/PP composites (0.36 J/mm). In addition, the flame-retardant properties of the composites were modified by three methods. The results showed that the composites composed of flame-retardant-modified denim fabric exhibited the limiting oxygen index value of 27.3%, much higher than that of the modified PP composites (<19.2%) and untreated composites (<19.2%). Composites made by using flame-retardant PP and modified denim fabric simultaneously attained highest limiting oxygen index at 28.7%. The discarded denim fabric/PP composites showed good mechanical and flame-retardant properties and thus could substitute the traditional composites in automotive interior, packing materials and engineering materials.

In recent decades, rational management of agricultural residues presented a new approach for extraction, characterization, and utilization of cellulose nanofibers (CNF). In this context, the valorization of flaxseed fibers, providing an annual yield of millions of metric tons, as an abundant sustainable fiber source, was carried out. The cleaned and ground raw material was delignified and bleached, followed by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)/NaBr/NaClO oxidization along with mechanical homogenization. The resulting extracted cellulose and cellulose nanofibers were characterized by various analytical methods. The overall yield of CNF based on the raw material was 31.2% ± 1.5%. This study explored a simple method for converting flaxseed fibers to fluorescent, high quality, nano-sized cellulosic precursors for novel applications in pharmaceutical and bio-composite applications.