Esterified cellulose nanofibres from saw dust using vegetable oil.

In this work, cellulose nanofibres (CNFs) were extracted from sawdust, which is an underutilized by-product from the wood and timber industry. The extracted CNFs by chemical and mechanical treatments had a web-like structure with diameters ranging between 2 nm and 27 nm and lengths reaching a few microns. The obtained CNFs were further chemically modified with vegetable canola oil using two different esterification processes. In order to compare the effect of the surface modification of CNFs, the nanopapers were prepared from their prospective suspensions through solvent evaporation method, and then characterize with Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), UV-vis spectroscopy and tensile tester. FTIR results indicated that both methods led to a successful grafting of the long chain hydrocarbon structure onto the CNFs, and became more hydrophobic when compared to unmodified CNFs-based nanopapers. The crystallinity, mechanical, light transmittance and thermal properties were significantly affected primarily by the esterification method employed, thus the degree of substitution. It was found that high degree of substitution adversely affected the crystallinity, light transmittance, mechanical and thermal properties. The crystallinity decreased from 70% to <40% when the degree of substation was about 0.8.

Thermoplastic Processing of PLA/Cellulose Nanomaterials Composites.

Over the past decades, research has escalated on the use of polylactic acid (PLA) as a replacement for petroleum-based polymers. This is due to its valuable properties, such as renewability, biodegradability, biocompatibility and good thermomechanical properties. Despite possessing good mechanical properties comparable to conventional petroleum-based polymers, PLA suffers from some shortcomings such as low thermal resistance, heat distortion temperature and rate of crystallization, thus different fillers have been used to overcome these limitations. In the framework of environmentally friendly processes and products, there has been growing interest on the use of cellulose nanomaterials viz. cellulose nanocrystals (CNC) and nanofibers (CNF) as natural fillers for PLA towards advanced applications other than short-term packaging and biomedical. Cellulosic nanomaterials are renewable in nature, biodegradable, eco-friendly and they possess high strength and stiffness. In the case of eco-friendly processes, various conventional processing techniques, such as melt extrusion, melt-spinning, and compression molding, have been used to produce PLA composites. This review addresses the critical factors in the manufacturing of PLA-cellulosic nanomaterials by using conventional techniques and recent advances needed to promote and improve the dispersion of the cellulosic nanomaterials. Different aspects, including morphology, mechanical behavior and thermal properties, as well as comparisons of CNC- and CNF-reinforced PLA, are also discussed.

Electrospun alginate nanofibres impregnated with silver nanoparticles: Preparation, morphology and antibacterial properties.

Silver nanoparticles are amongst the most valuable nanoparticles with interesting properties, such as a non-toxic nature and high antibacterial efficiency, making them applicable for tissue scaffold, protective clothing and wound dressing. In this study, silver nanoparticles (AgNPs) have been synthesized using chitosan as reducing and stabilizing agent. The formation of silver nanoparticles was confirmed by UV-vis, and the TEM showed that different shapes were obtained depending on the heating duration. The chitosan/AgNPs was coated onto an electrospun alginate membrane to produce stable polyelectrolyte complex (PEC) nanofibre composites with high antibacterial efficiency. These composites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). AgNPs were successfully impregnated into the PEC nanofibre composite, while there was complexation between the electrospun alginate and the chitosan/AgNPs composite. PEC demonstrated a good antibacterial activity against both gram negative and gram positive bacteria with acceptable water vapour transmission within the range required for the treatment of injuries or wounds.