To control and predict lignin properties remains very challenging due to the complexity of chemical structures and recovery methods of lignin. Recently, an acid-catalyzed one-pot liquefaction technique was developed to produce Kraft lignin with improved molecular uniformity directly from black liquor. Herein, we investigated the effects of the liquefaction parameters (pH, reaction temperature, and reaction time) on the yield, molecular weights, polydispersity, and quantities of different types of hydroxyl groups of the Kraft lignin using the Box–Behnken response surface methodology (RSM). Computational models were generated and refined to establish the relationships between the liquefaction parameters and the Kraft lignin properties. The results showed that pH was the most influential factor followed by the reaction temperature affecting the properties of the Kraft lignin. The yield, molecular weight, and polydispersity were found to be more predictable (R(pred)2 values of 87.5–91.5%) than the type and quantity of hydroxyl groups (R(pred)2 values of 0) of the Kraft lignin. Additionally, the weight average molecular weight (Mw) could be used as a reliable predictor for both the number average molecular weight (Mn) and the polydispersity of the Kraft lignin, which was confirmed by both the experimental and the computational approaches. Such tunable and predictable molecular properties of the lignin may be associated with the combination of acetic acid, subcritical methanol, and one-pot method. This study provided insights into understanding, predicting, and even customizing the properties of the lignin products.
The mechanical properties of phenolic resin reinforced with three different carbon materials were investigated experimentally. The carbon materials: (1) commercially produced carbon nanotubes (CNTs), (2) flash-heated lignocellulose containing CNTs and carbon-black, and (3) cyclically oxidized lignocellulose (Goodell, B. et al. (2008). Journal of Nanoscience and Nanotechnology, 8: 2472-2474) were added to phenolic resin in different weight percentages to fabricate composites. Carbon nanotubes were found to be an effective reinforcing filler increasing tensile strength by 45.34% and Young’s modulus by 19.08% with a 2% loading. The flash-heated material increased Young’s modulus by 11.04% with a 2% loading but did not affect tensile strength. The cyclically heated material did not contain CNTs, their inclusion in the composites reduced Young’s modulus and, for the 1% loading, reduced tensile strength as well.
The strive for utilization of green fillers in polymer composite has increased focus on application of natural biomass-based fillers. Biochar has garnered a lot of attention as a filler material and has the potential to replace conventionally used inorganic mineral fillers. Biochar is a carbon rich product obtained from thermochemical conversion of biomass in nitrogen environment. In this review, current studies dealing with incorporation of biochar in polymer matrices as a reinforcement and conductive filler were addressed. Each study mentioned here is nuanced, while addressing the same goal of utilization of biochar as a filler. In this review paper, an in-depth analysis of biochar and its structure is presented. The paper explored the various methods employed in fabrication of the biocomposites. A thorough review on the effect of addition of biochar on the overall composite properties showed immense promise in improving the overall composite properties. An analysis of the possible knowledge gaps was also done, and improvements were suggested. Through this study we tried to present the status of application of biochar as a filler material and its potential future applications.
In the modern forest industry, the need for bio-based, renewable, and environmentally-benign wood preservatives is increasing. The world harvests approximately 1700 million m3 of wood annually for use in a variety of applications. Unfortunately, when exposed to moisture, wood products are at high risk of decay by wood degrading fungi. Preservatives are used to prevent or limit decay, and there has been an increasing interest in developing wood preservatives from renewable materials. For this work, the effectiveness of water-dispersible, double-shell, lignin nanocapsules encapsulating the fungicide propiconazole, as a sustainable wood preservative, was evaluated. The system was tested for its biocidal efficacy against brown rot decay by Gloeophyllum trabeum in southern yellow pine wood using both dip and pressure treatments. The preservative successfully penetrated the wood block during pressure treatment, and following 3 months of soil-jar incubation, only wood blocks pressure-treated with either the double-shelled-propiconazole nanocapsule system or the conventional exterior wood preservative, chromated copper arsenate (CCA), showed less weight loss (19.95 ± 2.05 and 16.40 ± 3.80%, respectively) compared to the control (41.58 ± 9.51%). Additionally, the novel preservative system exhibited enhanced antifungal resistance compared to its individual constituents, as confirmed with Kirby–Bauer disk diffusion tests. The double-shell lignin nanocapsule exhibited radical quenching activity against DPPH of 75.9 ± 4.2%, and this could have contributed to the enhanced antifungal activity of the double-shell lignin nanocapsule–propiconazole system. This novel preservative system can be considered as a potential bio-based antifungal wood preservative.
Abstract Effects of the heating rate on the physical properties of carbonized wood were investigated by comparing the dimensional shrinkage, electrical resistivity, Young's modulus, and the evolution of turbostratic crystallites in maple hardwood samples carbonized at 600°C, 800°C, and 1000°C under heating regimes of 3°C h -1 and 60°C h -1 . Important carbonized wood properties that developed at high temperature and high heating rates could also be produced at slow heating rates and lower temperatures. Furthermore, slow heating rates promoted the formation and growth of graphene sheets in turbostratic crystallites, which had a significant influence on the electrical resistivity and Young's modulus of the carbonized wood. The results indicate that the graphene sheets of turbostratic crystallites formed during wood carbonization were arranged parallel to the axial direction of wood cells and at an angle to the circumference of wood cells in the cross-sectional plane. With regard to the production of carbon products, a decrease in the heating rate may be beneficial for char properties and the prevention of crack production during manufacture of large monolithic carbon specimens from wood and wood-based materials.
A highly convenient copper(I)-catalyzed oxidation-initiated cyclopropanation of indolyl ynamide for the rapid construction of indole-fused cyclopropane-lactams is described, which represents, to the best of our knowledge, the first non-noble-metal-catalyzed indolyl ynamide oxidation/dearomatization by the in situ generated α-oxo copper carbenes. Compared to hydrazone and diazo, the use of alkynes as carbene precursors allows cyclopropanation to occur under a safe and convenient pathway. Moreover, this transformation can lead to the divergent synthesis of pentacyclic spiroindolines involving the reversal of ynamide regioselectivity by engineering substrate structures.
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