Urushi as a Green Component for Thermally Curable Colloidal Lignin Particles and Hydrophobic Coatings.

Colloidal lignin nanoparticles are promising building blocks for sustainable functional materials. However, their instability in organic solvents and aqueous alkali limits their applicability. Current stabilization methods require nonrenewable and toxic reagents or tedious workup procedures. Here we show a method to prepare hybrid nanoparticles using only natural components. Urushi, a form of black oriental lacquer, and lignin are coaggregated to form hybrid particles, with Urushi acting as a sustainable component that stabilizes the particles via hydration barrier effect and thermally triggered internal cross-linking. The weight fractions of the two components can be adjusted to achieve the desired level of stabilization. Hybrid particles with Urushi content >25 wt % undergo interparticle cross-linking that produces multifunctional hydrophobic protective coatings that improve the water resistance of wood. This approach provides a sustainable and efficient method for stabilizing lignin nanoparticles and opens up neoteric possibilities for the development of lignin-based advanced functional materials.

Surface analysis of novel fibroin films based on well-preserved crystalline structures.

We recently reported that a highly homogeneous aqueous suspension of fibroin nanofiber (FNF) can be simply obtained by mechanical water-grinding a heterogeneous aqueous fibroin slurry and that the FNF in the suspension preserves the native ß-sheet secondary structure during this mechanical treatment. The current study reports the surface properties of well-preserved crystalline structure novel FNF film from water-grinding preparation as compared with those of typical, conventionally prepared regenerated fibroin (RF) film. RF film was not treated with alcoholic solutions and was verified to be amorphous from a WAXD diffraction diagram. The air-side surfaces of the FNF semi-crystalline and RF amorphous films were studied to clarify differences using scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), static water contact angle, and X-ray photoelectron spectroscopy (XPS). The well-preserved crystalline in the FNF film was found to exist near a slightly deep surface region and to act as a physically cross-linking domain, governing the molecular motions of the amorphous polypeptide chains at the very shallow surface region.

Effect of cellulose nanocrystals derived from Dunaliella tertiolecta marine green algae residue on crystallization behaviour of poly(lactic acid).

Marine green algae biomass residue (ABR), a waste by-product of Dunaliella tertiolecta, left behind after the extraction of oil from the algal biomass, was utilized for the fabrication of cellulose nanocrystals (CNCs). The fabricated sulphuric acid hydrolysed CNCs had needle-like morphology, with dominant cellulose type I polymorph and a high crystallinity index of 89 %. ICP-MS elemental analysis confirmed the presence of a variety of minerals in the ABR. Washed ABR (WABR)/PLA and CNC/PLA bio-composite films were developed via solvent casting technique with varying bio-filler loadings for comparing their effectiveness on the crystallization behaviour of PLA. FESEM, FTIR, XRD and TGA were used to characterize the bio-fillers. The nucleating and crystallization behaviour of the bio-composite films were confirmed using DSC, SAXS and POM analysis which indicated better effectiveness of CNCs with a significant reduction in cold crystallization temperature, and noteworthy increment in crystallinity and spherulite growth rate.

Reconstruction of Fibroin Nanofibers (FNFs) via Electrospinning: Fabrication of Poly(vinyl alcohol)/FNFs Composite Nanofibers from Aqueous Solution.

Fibroin nanofibers (FNFs) achieved from physical treated silk can keep its original crystal structure, showing excellent mechanical properties, however, processing the FNFs into fibers is still a challenge. Herein, a brand-new environmentally friendly approach is proposed to manufacture FNFs-based composite nanofibers. The water-soluble polymer, poly(vinyl alcohol) PVA, was applied to increase the viscoelasticity of the spinning dope, and the content of FNFs can reach up to 20 wt%. The established phase image of spinning suggested that the concentrations ranging from 6 wt% to 8 wt% are premium to achieving relatively homogenous FNFs/PVA nanofibers. Random fibers were deposited on a fixed collector, while the fiber orientation intensity increased with the rotational speed of drum and started decreasing after 12 m/s. The mechanical properties of the composite nanofibers showed the similar tendency of variation of fiber orientation. In addition, chemical changes, crystallinity, and thermal properties of the composite nanofibers were further clarified by means of FTIR, DSC, and TG. As a result, high FNFs contained nanofibers with excellent thermal properties were created from an aqueous solution. This study is the first original work to realize the spinnability of FNFs, which provides a new insight of the FNFs.

Comparison of polyvinyl alcohol films reinforced with cellulose nanofibers derived from oil palm by impregnating and casting methods.

Cellulose nanofibers (CNFs) derived from oil palm trees were utilized to reinforce polyvinyl alcohol (PVA) films by either casting or impregnating. CNFs derived from trunks of the oil palm tree were dispersed well in a PVA film by the casting method. Using the impregnating method, however, a sandwich construction with CNFs and PVA was obtained, which was confirmed using attenuated total reflectance Fourier transform infrared spectroscopy. The thermal stability, tensile strength, and Young's moduli of the PVA/CNF nanocomposite films were increased by compounding CNFs at different concentrations using both the casting and impregnating methods. However, the impregnated nanocomposite films showed higher thermal melting temperature and higher tensile toughness than those obtained by the casting method. No obvious differences appeared in the X-ray diffraction patterns or thermal decomposition behavior between the impregnated and cast nanocomposite films. In addition, adding CNFs was confirmed to increase the crystallinity of PVA.

Characterization of Ground Silk Fibroin through Comparison of Nanofibroin and Higher Order Structures.

Silk fibroin, a biodegradable component of silk, is increasingly used for various applications and studied intensively. Recently, a technique for preparing nanofibers without using chemicals has been gaining attention from the environmental impact and safety perspectives. This study focuses on the structure observation of ground silk fibroin (GF) prepared using a grinding method, which is a physical nanofibrillation method. The fabricated nanofiber samples were examined in detail using the X-ray diffraction (XRD), differential scanning calorimetry (DSC), micro Raman spectroscopy, and atomic force microscopy (AFM) techniques. The nanofibrillated structures were observed in both GF and regenerated silk fibroin (RF) samples prepared using the conventional method. As results, AFM images showed that the nanofibril diameter of GF was about 1.64 nm and that of RF was about 0.32 nm. Methanol treatment induced a structural transition from a random coil to a ß-sheet for the RF film, but it had no effect on the GF film. Thus, it is suggested that the grinding method provides not only ultrafine silk fibroin nanofibers without using toxic reagents but also resistance to reagents such as methanol.

Comparison of cellulose nanofiber properties produced from different parts of the oil palm tree.

Cellulose nanofibers (CNFs) were obtained from three types of oil palm wastes, mesocarp, empty fruit bunch (EFB), and palm kernel shell (PKS), as well as the trunk of the oil palm tree, to compare their morphological, thermal, and mechanical properties. Despite large differences in the chemical components of cell walls in the raw materials, the production of CNFs from all parts of the oil palm were achieved in this work. The morphology and mechanical properties of the CNF sheets obtained from the trunk had advantages over the CNF sheets from wastes, while the thermal degradation properties showed no advantage. Cellulose crystallinity of the CNF sheet from the mesocarp and PKS had lower crystallinity (69.1 and 71.1%), and the highest crystallinity of 77.0% was exhibited by the sheet from the trunk. The value of specific tensile strength and specific Young's modulus were highest in the CNF sheet of the trunk, and lowest mechanical properties shown in the CNF sheet from the mesocarp. These results strongly suggested that the CNF could be obtained from all parts of the plants, but their properties may vary.