Effect of silane modified microcrystalline cellulose on the curing kinetics, thermo-mechanical properties and thermal degradation of benzoxazine resin

Elastic and Self-Healing Copolymer Coatings with Antimicrobial Function

The revolutionary self-healing function for long-term and safe service processes has inspired researchers to implement them in various fields, including in the application of antimicrobial protective coatings. Despite the great advances that have been made in the field of fabricating self-healing and antimicrobial polymers, their poor transparency and the trade-off between the mechanical and self-healing properties limit the utility of the materials as transparent antimicrobial protective coatings for wearable optical and display devices. Considering the compatibility in the blending process, our group proposed a self-healing, self-cross-linkable poly{(n-butyl acrylate)-co-[N-(hydroxymethyl)acrylamide]} copolymer (AP)-based protective coating combined with two types of commercial cationic antimicrobial agents (i.e., dimethyl octadecyl (3-trimethoxysilylpropyl) ammonium chloride (DTSACL) and chlorhexidine gluconate (CHG)), leading to the fabrication of a multifunctional modified compound film of (AP/b%CHG)-grafted-a%DTSACL. The first highlight of this research is that the reactivity of the hydroxyl group in the N-(hydroxymethyl)acrylamide of the copolymer side chains under thermal conditions facilitates the "grafting to" process with the trimethoxysilane groups of DTSACL to form AP-grafted-DTSACL, yielding favorable thermal stability, improvement in hydrophobicity, and enhancement of mechanical strength. Second, we highlight that the addition of CHG can generate covalent and noncovalent interactions in a complex manner between the two biguanide groups of CHG with the AP and DTSACL via a thermal-triggered cross-linking reaction. The noncovalent interactions synergistically serve as diverse dynamic hydrogen bonds, leading to complete healing upon scratches and even showing over 80% self-healing efficiency on full-cut, while covalent bonding can effectively improve elasticity and mechanical strength. The soft nature of CHG also takes part in improving the self-healing of the copolymer. Moreover, it was discovered that the addition of CHG can enhance antimicrobial effectiveness, as demonstrated by the long-term superior antibacterial activity (100%) against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria and the antifouling function on a glass substrate and/or a silica wafer coated by the modified polymer.

Improved lipase performance by covalent immobilization of Candida antarctica lipase B on amino acid modified microcrystalline cellulose as green renewable support

Development of immobilized lipase with excellent catalytic performance and low cost is the major challenge for large-scale industrial applications. In this study, green renewable microcrystalline cellulose (MCC) that was hydrophobically modified with D-alanine (Ala) or L-lysine (Lys) was used for immobilizing Candida antarctica lipase B (CALB). The improved catalytic properties were investigated by experimental and computational methods. CALB immobilized on MCC-Ala with higher hydrophobicity showed better catalytic activity than CALB@MCC-Lys because the increased flexibility of the lid region of CALB@MCC-Ala favored the formation of open conformation. Additionally, the low root mean square deviation and the high β-sheet and α-helix contents of CALB@MCC-Ala indicated that the structure became more stable, leading to a significantly enhanced stability (54.80% and 90.90% relative activity at 70 °C and pH 9.0, respectively) and good reusability (48.92% activity after 5 cycles). This study provides a promising avenue to develop immobilized lipase with high catalytic properties for industry applications.

Cellulose microfiber extraction from leftover celery pulp: Chemomechanical treatments, structural, morphological, and thermal characterization

Based on the variety of attractive applicability and structural advantages, cellulose is suggested as a sustainable and environmentally-friendly replacement for petroleum-based materials. Therefore, the current study proposed two chemo-mechanical treatments including bleaching with sodium chlorite and sodium hypochlorite for pure cellulose extraction from leftover celery pulp (Apium graveolens var. dulce). The characterizations of the extracted cellulose fibers were measured and analyzed, by using FT-IR, XRD, optical microscopy, FE-SEM, and TGA analysis. FTIR analysis confirmed the successful removal of non-cellulosic and impurities materials by chemical treatments. Analyzing the X-ray diffraction showed that the proposed chemo-mechanical procedures did not have damaging impacts on the cellulose crystalline structure. Microscopies analysis within optical microscopy and FE-SEM indicated that the diameters of the untreated fibers generally ranged from 100 to 150 μm, while for the treated ones, they ranged from 10 to 15 μm. The TGA results illustrated the higher initial degradation temperatures for the treated samples which led to significant improvement in their thermal stabilities.

Extraction and characterization of natural lignocellulosic fibres from Typha angustata grass

In recent years, efforts have been made to reduce deforestation to conserve the ecosystem. In the current scenario, agro-cultivated products are used instead of wood for engineering applications. Thus, natural lignocellulosic fibres are used as a reinforcing material and have been extremely attractive to industries and the scientific community during the past few decades. This study aimed to examine the use of natural fibres extracted from Typha angustata grass as reinforcement in polymer matrix composites. The density of the fibres was 1.015 g/cc. Chemical analysis confirmed that T. angustata fibres (TAFs) have a cellulose content of 73.54 wt%, a hemicellulose content of 10.11 wt%, a lignin content of 6.23 wt% and a wax content of 0.23 wt%. The crystallinity index (65.16 %) and crystalline size (6.40 nm) were identified by X-ray diffraction (XRD) analysis. The presence of functional groups in the TAFs was examined by employing Fourier-transform infrared spectroscopy (FTIR). The presence of cellulose at peak intensities of C2, C3 and C5 in the TAFs was confirmed using ¹³C nuclear magnetic resonance (NMR) spectroscopy. The single fibre tensile test revealed that the tensile strength was 665 ± 7 MPa and Young's modulus was 27.45 ± 3.46 GPa. The thermal stability of the TAFs was examined by thermogravimetric analysis (TGA), and the prominent peak was observed at 298.48 °C, with a kinetic activation energy of 67.99 kJ/mol. The surface roughness of the fibres was analysed by atomic force microscopy (AFM) with an accuracy of 1 nm. The above-mentioned outcomes indicated that the TAFs have desirable properties that are comparable to existing natural fibres and suggested to be utilised as the possible reinforcement to fabricate the fibre-reinforced polymer matrix composites.