Nanocellulose from Unbleached Hemp Fibers as a Filler for Biobased Photocured Composites with Epoxidized Cardanol

Thermal, mechanical, and morphological properties of oil palm cellulose nanofibril reinforced green epoxy nanocomposites

In this study, significant improvements in mechanical properties have been seen through the efficient inclusion of Oil Palm Cellulose Nanofibrils (CNF) as nano-fillers into green polymer matrices produced from biomass with a 28 % carbon content. The goal of the research was to make green epoxy nanocomposites utilizing solution blending process with acetone as the solvent with the different CNF loadings (0.1, 0.25, and 0.5 wt%). An ultrasonic bath was used in conjunction with mechanical stirring to guarantee that CNF was effectively dispersed throughout the green epoxy. The resultant nanocomposites underwent thorough evaluation, comparing them to unfilled green epoxy and evaluating their morphological, mechanical, and thermal behavior using a variety of instruments. Field-emission scanning electron microscopy (FE-SEM) was used to validate findings, which showed that the CNF were dispersed optimally inside the nanocomposites. The thermal degradation temperature (Td) of the nanocomposites showed a marginal decrement of 0.8 % in temperatures (from 348 °C to 345 °C), between unfilled green epoxy (neat) and 0.1 wt% of CNF loading. The mechanical test results, which showed a 13.3 % improvement in hardness and a 6.45 % rise in tensile strength when compared to unfilled green epoxy, were in line with previously published research. Overall, the outcomes showed that green nanocomposites have significantly improved in performance.

Biobased Composites by Photoinduced Polymerization of Cardanol Methacrylate with Microfibrillated Cellulose

Biobased monomers and green processes are key to producing sustainable materials. Cardanol, an aromatic compound obtained from cashew nut shells, may be conveniently functionalized, e.g., with epoxy or (meth)acrylate groups, to replace petroleum-based monomers. Photoinduced polymerization is recognized as a sustainable process, less energy intensive than thermal curing; however, cardanol-based UV-cured polymers have relatively low thermomechanical properties, making them mostly suitable as reactive diluents or in non-structural applications such as coatings. It is therefore convenient to combine them with biobased reinforcements, such as microfibrillated cellulose (MFC), to obtain composites with good mechanical properties. In this work a cardanol-based methacrylate monomer was photopolymerized in the presence of MFC to yield self-standing, flexible, and relatively transparent films with high thermal stability. The polymerization process was completed within few minutes even in the presence of filler, and the cellulosic filler was not affected by the photopolymerization process.

Valorization of Byproducts of Hemp Multipurpose Crop: Short Non-Aligned Bast Fibers as a Source of Nanocellulose

Nanocellulose was extracted from short bast fibers, from hemp (Cannabis sativa L.) plants harvested at seed maturity, non-retted, and mechanically decorticated in a defibering apparatus, giving non-aligned fibers. A chemical pretreatment with NaOH and HCl allowed the removal of most of the non-cellulosic components of the fibers. No bleaching was performed. The chemically pretreated fibers were then refined in a beater and treated with a cellulase enzyme, followed by mechanical defibrillation in an ultrafine friction grinder. The fibers were characterized by microscopy, infrared spectroscopy, thermogravimetric analysis and X-ray diffraction after each step of the process to understand the evolution of their morphology and composition. The obtained nanocellulose suspension was composed of short nanofibrils with widths of 5-12 nm, stacks of nanofibrils with widths of 20-200 nm, and some larger fibers. The crystallinity index was found to increase from 74% for the raw fibers to 80% for the nanocellulose. The nanocellulose retained a yellowish color, indicating the presence of some residual lignin. The properties of the nanopaper prepared with the hemp nanocellulose were similar to those of nanopapers prepared with wood pulp-derived rod-like nanofibrils.

Photoinduced Processes as a Way to Sustainable Polymers and Innovation in Polymeric Materials

Photoinduced processes have gained considerable attention in polymer science and have greatly implemented the technological developments of new products. Therefore, a large amount of research work is currently developed in this area: in this paper we illustrate the advantages of a chemistry driven by light, the present perspectives of the technology, and summarize some of our recent research works, honoring the memory of Prof. Aldo Priola who passed away in March 2021 and was one of the first scientists in Italy to contribute to the field.