Structural analyses of supernatant fractions in TEMPO-oxidized pulp/water reaction mixtures separated by centrifugation and dialysis.

Side reactions occurring on cellulose during 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TMEPO)-catalyzed oxidation have not been considered to be significant. Then, TEMPO-oxidized hardwood and softwood bleached kraft pulps (HBKP and SBKP) were prepared with an excess NaOCl·5H2O. Supernatant fractions (SFs) were obtained in the aqueous reaction mixtures of TEMPO-oxidized pulps by centrifugation and dialysis. The SFs with carboxyl contents of 5.0 and 4.2 mmol/g were obtained in the yields of 19 % and 30 % from HBKP and SBKP, respectively. These carboxy contents are much higher than those (2.6-2.7 mmol/g) of the precipitate fractions in the TEMPO-oxidized pulps. Solid-state 13C NMR spectra and other analyses revealed that the water-soluble ß-(1 â†’ 4)-polyglucuronic acids were predominantly present in the SFs. In addition, water-insoluble TEMPO-oxidized cellulose nanocrystals were present in the SFs, but they constituted less than ~10 % of the SFs. The mass-average degrees of polymerization (DPw) of the SFs obtained from HBKP and SBKP were 166 and 155, respectively, whereas the original HBKP and SBKP had DPw values of 1990 and 2140, respectively. These substantial depolymerization and formation of the water-soluble ß-(1 â†’ 4)-polyglucuronic acids occur on cellulose and oxidized cellulose molecules as side reactions during TEMPO-catalyzed oxidation, which should be considered for structural analyses of TEMPO-oxidized products.

Correction to "Comprehensive Study of Preparation of Carboxy Group-Containing Cellulose Fibers from Dry-Lap Kraft Pulps by Catalytic Oxidation with Solid NaOCl".

[This corrects the article DOI: 10.1021/acssuschemeng.3c04750.].

Polyglucuronic acids prepared from α-(1 → 3)-glucan by TEMPO-catalytic oxidation.

2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO)-catalytic oxidation was applied to a water-insoluble α-(1 â†’ 3)-glucan in water at pH 10 and room temperature (∼24 °C), with solid NaOCl·5H2O as the primary oxidant. Oxidation with NaOCl at 15 mmol/g gave a water-soluble TEMPO-oxidized product at a mass recovery ratio of 97 %. The carboxy content of the TEMPO-oxidized product was 5.3 mmol/g, which corresponds to a degree of C6-oxidation (DO) of 93 %. A new water-soluble α-(1 â†’ 3)-polyglucuronic acid with a nearly homogeneous chemical structure was therefore quantitatively obtained. X-ray diffraction and solid-state 13C NMR spectroscopic analyses showed that the original α-(1 â†’ 3)-glucan and its TEMPO-oxidized product with a carboxy content of 5.3 mmol/g had crystalline structures, whereas the oxidized products with DOs of 50 % and 66 % had almost disordered structures. The carboxy groups in the oxidized products were regioselectively methyl esterified with trimethylsilyl diazomethane, and analyzed by using size-exclusion chromatography with multi-angle laser-light scattering and refractive index detections. The results show that the original α-(1 â†’ 3)-glucan and its oxidized products with DOs of 50 %, 66 %, and 93 % had weight-average degrees of polymerization of 671, 288, 54, and 45, respectively. Substantial depolymerization of the α-(1 â†’ 3)-glucan molecules therefore occurred during catalytic oxidation, irrespective of the oxidation pH.

Properties of mixture of hemp bast and softwood pulp for filter paper manufacture.

The objective of this study was to investigate the morphological and chemical properties of hemp bast RPF1 variety fiber to be used as a potential raw material for filter paper production. Experimental handsheet samples with basis weight of 20 g/m2 were manufactured using mixture of hemp and softwood pulp at various beating levels. The average fiber length and width of hemp bast fiber were determined as 5.76 mm and 32.53 µm, respectively. It was also found that the hemp bast fiber had rigid thick cell wall with small size of lumen. The overall chemical properties of hemp bast were similar to those fibers from other bast sources as well as softwood fibers. It seems that hemp bast was easily pulped under various soda process conditions yielding pulp ranging from 51.36 % to 52.56 % and Kappa numbers ranging from 2.89 to 8.18. Based on the findings in this study hemp bast fiber could be considered as a potential to manufacture filter paper with accepted characteristics.

Morphology, Taxonomy, Culm Internode and Leaf Anatomy, and Palynology of the Giant Reed (Arundo donax L.), Poaceae, Growing in Thailand.

In this paper, we present the morphology, taxonomy, anatomy, and palynology of Arundo donax. A detailed morphological description and illustrations of the species are provided, along with information about the identification, distribution, the specimens examined, habitat and ecology, the International Union for Conservation of Nature (IUCN) conservation assessment, phenology, etymology, vernacular name, and uses. The species can be distinguished by its large, tall rhizomatous perennial reed; cauline leaves; an open, large, plumose panicle inflorescence; subequal glumes as long as the spikelets; glabrous rachilla; all bisexual florets; and a lemma with a straight awn and with long white hairs outside below the middle part. In this study, two names were lectotypified: Arundo bifaria and A. bengalensis, which are synonyms of A. donax. The culm internodes in the transverse section have numerous vascular bundles scattered in the ground tissue, and the parenchyma cells have significantly lignified cell walls. Vascular bundles are composed of phloem and xylem and are enclosed in a continuous sclerenchymatous bundle sheath. The chloroplasts in the transverse section of the leaf blades are found only in the mesophyll cells but are absent in the bundle sheath cells, which indicates that it is a C3 grass. The leaves have stomata on both surfaces and are confined to the intercostal zones. The stomata are typically paracytic, with two lateral subsidiary cells placed parallel to the guard cells. The stomatal density is higher on the abaxial surface [450-839/mm2 (606.83 ± 72.71)] relative to the adaxial surface [286-587/mm2 (441.27 ± 50.72)]. The pollen grains are spheroidal or subspheroidal [polar axis length/equatorial axis length ratio (P/E ratio) = 0.89-1.16 (1.02 ± 0.07)] with a single pore surrounded by a faint annulus, and the exine sculpturing is granular.

TEMPO-oxidized cellulose nanofibril film from nano-structured bacterial cellulose derived from the recently developed thermotolerant Komagataeibacter xylinus C30 and Komagataeibacter oboediens R37-9 strains.

Bacterial cellulose (BC), prepared from two recently developed thermotolerant bacterial strains (Komagataeibacter xylinus C30 and Komagataeibacter oboediens R37-9), were used as a raw material to synthesize nanofibril films. Field-emission scanning electron microscope (FE-SEM) observations confirmed the ultrafine nano-structure of BC pellicle (BCP) with average fibril widths between 50 and 60 nm. The BC was directly oxidized in a TEMPO/NaBr/NaClO system at pH of 10 for 2 h. TEMPO-oxidized bacterial cellulose nanofibrils (TOBCN) were obtained by a mild mechanical treatment and the TOBCN films were prepared through heat-drying. The oxidation yielded a recovery ratio between 70 and 80% by weight with an increase in the carboxylate content of 0.9-1.0 mmol g -1. Nanofibrillation yields were more than 90% and the resulting high aspect ratio TOBCNs were ~6 nm in average width with >800 nm in lengths, when observed under transmission electron microscope (TEM). TOBCN film of K. xylinus C30 exhibited high transparency (79%), tensile strength (142 MPa), Young's modulus (7.13 GPa), elongation around failure (3.89%), and work of fracture (2.29 MJ m-3), when compared to the TOBCN films of K. oboediens R37-9 at 23 °C and 50% RH. Coefficients of thermal expansion of both the TOBCN films were low at around 6 ppm K-1.

Basalt-Fiber-Reinforced Polyvinyl Acetate Resin: A Coating for Ductile Plywood Panels.

The aim of this study was to create a reinforced composite wood-based panel that would be leaned towards the environment Plywood was used as a core material and fiber-reinforced polymer was used as a reinforcement. Conventional resin for the fiber-reinforced polymer was substituted with polyvinyl acetate (PVAC), which has several advantages, such as a lower price, easier handling, and better degradability. The second chosen component, basalt fiber, is cost attractive and environmentally friendly. The combination of one and two layers of fabric with three fiber fractions and 4 mm thick plywood was investigated. The best results were achieved with two layers of fabric and the highest fiber fraction. The improvements of the ultimate bending load and bending stiffness of the plywood in the perpendicular direction were 305% and 325%, respectively. The ultimate load and stiffness of the parallel direction were improved by 31% and 35%, respectively. However, specimens always failed in the compressional zone. The highest reinforcing effect was found with the impact test: The energy required to fracture specimens increased by 4213% and 6150% for one and two layers of fabric, respectively. In conclusion, specimens exhibited high ductility due to the PVAC and basalt fiber. The amount of work and energy required to cause fractures was extensive.