The effect of morphological changes from pulp fiber towards nano-scale fibrillated cellulose on the mechanical properties of high-strength plant fiber based composites

Fibrillated kraft pulp impregnated with phenolic resin was compressed under an extremely high pressure of 100MPa to produce high strength cellulose nanocomposites. To evaluate how the degree of fibrillation of pulp fiber affects the mechanical properties of the final composites, kraft pulp subjected to various levels of refining and high pressure homogenization treatments was used as raw material with different phenolic resin contents. It was found that fibrillation solely of the surface of the fibers is not effective in improving composite strength, though there is a distinct point in the fibrillation stage at which an abrupt increase in the mechanical properties of composites occurs. In the range between 16 and 30 passes through refiner treatments, pulp fibers underwent a degree of fibrillation that resulted in a stepwise increment of mechanical properties, most strikingly in bending strength, which increase was attributed to the complete fibrillation of the bulk of the fibers. For additional high pressure homogenization-treated pulps, composite strength increased linearly against water retention values, which characterize the cellulose’s exposed surface area, and reached maximum value at 14 passes through the homogenizer

EASY CELLULOSE NANOFIBER EXTRACTION FROM RESIDUE OF AGRICULTURAL CROPS

Cellulose is found in the cell wall of plant fibers in the form of nanofibers. The Young’s modulus of the crystalline portion is close to 140 GPa whereas the tensile strength of nanofibers is estimated to be above 2 GPa. Cellulose nanofiber has the potential to become an environmentally benign substitute for conventional reinforcements, but the overall cost of production is prohibitive due to the high energy demand and low yields of the mainstream processes, along the need of expensive devices for proper extraction. This study proposes the use of an affordable kitchen blender adapted to extract cellulose nanofiber from agricultural crop byproducts to reduce production cost. Preliminary results showed that blending of pulp fibers from grass straw produces nanofibers similar to commercially available morphologies. So far the raw material for nanofiber extraction has been mainly pulp fibers from wood, but the availability of cellulose in plant cells other than fibers would make nanofibers accessible to a wider research community and accelerate the development of cellulose-based nanocomposites

EXTRACTION OF CELLULOSE NANOFIBER FROM PARENCHYMA CELLS OF AGRICULTURAL RESIDUES

Cellulose nanofiber is an environmentally friendly reinforcing phase extractable from plants, with potential application in composites. Due to the cell wall structure differences, plant parenchyma cells might be easier to nanofibrillate than sclerenchyma cells of wood pulp fibers, resulting in lower extraction costs. This study assessed the extraction of nanofibers from residues like corn husk, banana peel, cabbage leaf, and taro leaf using a kitchen blender. Fibrillation was evaluated based on the strength of paper-like sheets produced from the nanofibers. Corn husk was nanofibrillated by the shortest blending time among the sources considered, and delivered the highest sheet strength. The blending time needed was significantly shorter than that needed to fibrillate hardwood pulp fibers

Cellulose nanofiber aerogel production and applications

Aerogels are highly porous solids formed by replacing the liquid in a gel by air, without changing the original structure. The present cellulose aerogels are made by sublimating the water from a colloidal suspension of cellulose nanofibers. The nanofibers form three-dimensional networks, crosslinked by hydrogen bonds bridging the surface hydroxyl groups and also by mechanical entanglements between nanofibers. Although the studies on aerogels from cellulose nanofiber hydrogels by freeze drying reported so far had produced small samples, improved cooling techniques that produces larger samples were attempted and the obtained cellulose nanofiber aerogels were impregnated with epoxy resin to fabricate composites. The highly porous structure allowed complete impregnation of resin and translucent composites were produced. The modulus of composites was increased in relation to neat epoxy, but due to high brittleness the ultimate strength was decreased. This is likely caused by nanofiber agglomerations of uneven pore sizes acting as stress concentrators. The evaluation of the mechanical properties of composites serves as an indirect way to assess the quality of the aerogels produced

Fabrication of Chitin Nanofiber-Reinforced PLA Nanocomposites by an Environmentally Friendly Process

Polylactic acid (PLA) reinforced with chitin nanofibers was produced from a mixture of a colloidal suspension of PLA particles with chitin nanofiber suspension. The dispersion medium was solely water, which was removed by filtration and drying. Nanocomposites were obtained by compression molding of the filtrates. Static tensile test and dynamic mechanical analysis were performed to evaluate the reinforcement as a function of nanofiber content. Chitin nanofibers delivered reinforcement similar to cellulose nanofibers, being especially effective at up to 70 wt% fiber load. The ultimate tensile modulus and strength reached 7.7 GPa and 110 MPa, respectively, at a nanofiber content of 70 wt%

Polylactic Acid Reinforced with Mixed Cellulose and Chitin Nanofibers : Effect of Mixture Ratio on the Mechanical Properties of Composites

The development of all-bio-based composites is one of the relevant aspects of pursuing a carbon-neutral economy. This study aims to explore the possibility to reinforce polylactic acid by the combination of cellulose and chitin nanofibers instead of a single reinforcement phase. Polylactic acid colloidal suspension, cellulose and chitin nanofiber suspensions were mixed using only water as mixing medium and subsequently dewatered to form paper-like sheets. Sheets were hot pressed to melt the polylactic acid and form nanocomposites. The combination of cellulose and chitin nanofiber composites delivered higher tensile properties than its counterparts reinforced with cellulose or chitin nanofibers alone. Cellulose and chitin appear to complement each other from the aspect of the formation of a rigid cellulose nanofiber percolated network, and chitin acting as a compatibilizer between hydrophobic polylactic acid and hydrophilic cellulose

On the use of nanocellulose as reinforcement in polymer matrix composites

AbstractNanocellulose is often being regarded as the next generation renewable reinforcement for the production of high performance biocomposites. This feature article reviews the various nanocellulose reinforced polymer composites reported in literature and discusses the potential of nanocellulose as reinforcement for the production of renewable high performance polymer nanocomposites. The theoretical and experimentally determined tensile properties of nanocellulose are also reviewed. In addition to this, the reinforcing ability of BC and NFC is juxtaposed. In order to analyse the various cellulose-reinforced polymer nanocomposites reported in literature, Cox–Krenchel and rule-of-mixture models have been used to elucidate the potential of nanocellulose in composite applications. There may be potential for improvement since the tensile modulus and strength of most cellulose nanocomposites reported in literature scale linearly with the tensile modulus and strength of the cellulose nanopaper structures. Better dispersion of individual cellulose nanofibres in the polymer matrix may improve composite properties