Nanocellulose-A Sustainable and Efficient Nanofiller for Rubber Nanocomposites: From Reinforcement to Smart Soft Materials

Cellulose nanocrystals extracted from rice husk using the formic/peroxyformic acid process: isolation and structural characterization

Cellulose derived from biomass is a renewable resource with numerous applications. Using formic/peroxyformic acid at atmospheric pressure, cellulose nanocrystals (CNC) were isolated from rice husk (RH) in this study. This method was an excellent way to get rid of lignin and hemicelluloses from RH. The cellulose was subsequently acid hydrolyzed by H2SO4 (64%) for 30 minutes at 45 °C. The chemical and microstructure analysis showed that the lignin and hemicellulose contents of raw RH had been eliminated, and the crystallinity content of CNC was 67.16%. According to transmission electron microscopy (TEM) morphological analysis, CNC measured 19 ± 3.3 nm in diameter, 195 ± 24 nm in length, and 10.2 ± 6.8 in aspect ratio. The thermal stability of RH and CNC was also investigated using thermogravimetric analysis (TGA). These encouraging findings demonstrated the potential for reusing RH agricultural waste to create CNC and include nanocomposites as a reinforcing material.

Low-temperature, ultra-fast, and recyclable self-healing nanocomposites reinforced with non-solvent silylated modified cellulose nanocrystals

Developing polymeric materials with remarkable mechanical properties and fast self-healing performance even at low temperatures is challenging. Herein, the polymeric nanocomposites containing silane-treated cellulose nanocrystals (SCNC) with ultrafast self-healing and exceptional mechanical characteristics were developed even at low temperatures. First, CNC is modified with a cyclic silane coupling agent using an eco-friendly chemical vapor deposition method. The nanocomposite was then fabricated by blending SCNC with matrix prepolymer, prepared from monomers that possess lower critical solution temperature, followed by the inclusion of dibutyltin dilaurate and hexamethylene diisocyanate. The self-healing capability of the novel SCNC/polymer nanocomposites was enhanced remarkably by increasing the content of SCNC (0-3 wt%) and reaching (≥99 %) at temperatures (5 & 25 °C) within <20 min. Moreover, SCNC-3 showed a toughness of (2498 MJ/m3) and SCNC-5 displayed a robust tensile strength of (22.94 ± 0.4 MPa) whereas SCNC-0 exhibited a lower tensile strength (7.4 ± 03 MPa) and toughness of (958 MJ/m3). Additionally, the nanocomposites retain their original mechanical properties after healing at temperatures (5 & 25 °C) owing to the formation of hydrogen bonds via incorporation of the SCNC. These novel SCNC-based self-healable nanocomposites with tunable mechanical properties offer novel insight into preparing damage and temperature-responsive flexible and wearable devices.

Understanding Nanocellulose-Water Interactions: Turning a Detriment into an Asset

Modern technology has enabled the isolation of nanocellulose from plant-based fibers, and the current trend focuses on utilizing nanocellulose in a broad range of sustainable materials applications. Water is generally seen as a detrimental component when in contact with nanocellulose-based materials, just like it is harmful for traditional cellulosic materials such as paper or cardboard. However, water is an integral component in plants, and many applications of nanocellulose already accept the presence of water or make use of it. This review gives a comprehensive account of nanocellulose-water interactions and their repercussions in all key areas of contemporary research: fundamental physical chemistry, chemical modification of nanocellulose, materials applications, and analytical methods to map the water interactions and the effect of water on a nanocellulose matrix.

Malleable and self-healing rubbers covalently crosslinked by reversible boronic ester bonds

Covalent cross-linking of rubbers is essential to obtain high elasticity, which plays a significant role in practical applications. Integrating dynamic covalent bonds into rubbers is a reliable way to endow them with self-healing capacity to repair damage and extend their service life. Herein, we propose a facile and effective method to introduce a crosslinking network composed of dynamic boronic ester bonds into epoxidized natural rubber (ENR). The reaction between dopamine-modified ENR and the hydrolysate of boric acid in weak alkaline solution formed a cross-linking network with reversible boronic ester bonds. Owing to the rearrangement of the crosslinked network initiated by the boronic ester exchange reaction, covalently crosslinked rubbers exhibit relatively better malleability and excellent self-healing ability under moderate conditions (60 °C/24 h).

Isolation and Characterization of Cellulose Nanocrystals from Date Palm Waste

This study presents the isolation, characterization, and kinetic analyses of cellulose nanocrystals (CNCs) from date palm waste in the United Arab Emirates. After bleaching date palm stem waste with acidified NaClO₂ and delignification via NaOH treatments, cellulose was extracted. Mineral acid hydrolysis (62 wt % H₂SO₄) was performed at 45 °C for 45 min to produce crystalline nanocellulose. Fourier transform infrared (FTIR) and chemical composition analysis confirmed the removal of noncellulosic constituents. The crystallinity index increased gradually with chemical treatments, according to the obtained X-ray diffraction (XRD) results. Thermogravimetric analysis and differential scanning calorimetry results revealed that the CNC has high thermal stability. The Coats-Redfern method was used to determine the kinetic parameters. The kinetic analysis confirmed that CNC has more activation energy than cellulose and thus confirms its compact and resistive crystalline structure. This has been attributable to the stronger hydrogen bonding in CNC crystalline domains than that in cellulose crystalline domains. Scanning electron microscopy revealed that lignin and hemicellulose were eliminated after chemical pretreatments, and CNC with a rodlike shape was obtained after hydrolysis. Moreover, transmission electron microscopy confirmed the nanoscale of crystalline cellulose. ζ potential analysis indicated that the CNC afforded a stable suspension (-29.27 mV), which is less prone to flocculation. Kinetic analyses of cellulose and cellulose nanocrystals isolated from date palm waste are useful for making composites and designing selective pyrolysis reactors.