Preparation and characterization of novel highly omniphobic cellulose fibers organic–inorganic hybrid materials

Starch-Silane Structure and Its Influence on the Hydrophobic Properties of Paper

Starch is an inexpensive, easily accessible, and widespread natural polymer. Due to its properties and availability, this polysaccharide is an attractive precursor for sustainable products. Considering its exploitation in adhesives and coatings, the major drawback of starch is its high affinity towards water. This study aims to explain the influence of the silane-starch coating on the hydrophobic properties of paper. The analysis of the organosilicon modified starch properties showed an enhanced hydrophobic behavior, suggesting higher durability for the coatings. Molecules of silanes with short aliphatic carbon chains were easily embedded in the starch structure. Longer side chains of silanes were primarily localized on the surface of the starch structure. The best hydrophobic properties were obtained for the paper coated with the composition based on starch and methyltrimethoxysilane. This coating also improved the bursting resistance and compressive strength of the tested paper. A static contact angle higher than 115° was achieved. PDA analysis confirmed the examined material exhibited high barrier properties towards water. The results extend the knowledge of the interaction of silane compositions in the presence of starch.

Preparation and Performance of Lignin-Based Multifunctional Superhydrophobic Coating

Superhydrophobic coatings have drawn much attention in recent years for their widespread potential applications. However, there are challenges to find a simple and cost-effective approach to prepare superhydrophobic materials and coatings using natural polymer. Herein, we prepared a kraft lignin-based superhydrophobic powder via modifying kraft lignin through 1H, 1H, 2H, 2H-perfluorodecyl-triethoxysilane (PFDTES) substitution reaction, and constructed superhydrophobic coatings by direct spraying the suspended PFDTES-Lignin powder on different substrates, including glass, wood, metal and paper. The prepared lignin-based coatings have excellent repellency to water, with a water contact angle of 164.7°, as well as good friction resistance, acid resistance, alkali resistance, salt resistance properties and quite good self-cleaning performance. After 30 cycles of sand friction or being stayed in 2 mol/L HCl, 0.25 mol/L NaOH and 2 mol/L NaCl solution for 30 min, the coatings still retain super hydrophobic capability, with contact angles higher than 150°. The superhydrophobic performance of PFDTES-Lignin coatings is mainly attributed to the constructed high surface roughness and the low surface energy afforded by modified lignin. This lignin-based polymer coating is low-cost, scalable, and has huge potential application in different fields, providing a simple way for the value-added utilization of kraft lignin.

Preparation and characterization of highly transparent hydrophobic nanocellulose film using corn husks as main material

In this paper, nanocellulose was extracted from agricultural waste corn husks. Transparent hydrophobic membranes containing silica were fabricated through two facile methods including surface coating and internal grafting. The results showed that: the nanocellulose prepared by TEMPO-mediated oxidation and high pressure homogenization not only retained the type and crystal structure of the original cellulose, but also increased the crystallinity to 64.5% and improved the thermal stability. Both surface coating and internal grafting methods had successfully loaded silica onto films. The internal grafting film had a silica content of 10.5%, which was mainly present inside the film. The light transmittance of this film was 84.4% and the surface contact angle to water was 152.6°. The content of silica on the surface coating film was 5.7%, and they were mainly distributed on the surface of the film to form a nano-scale rough surface. The light transmittance of the surface coating film was 87.8% and the surface contact angle to water was 165.7°. Compared to the film prepared by internal grafting method, the nanocellulose film prepared by surface coating method contained less nano silica and had better properties including higher transparency, higher surface roughness and excellent hydrophobic anti-fouling properties.

Fabrication of new conductive surface-metallized UHMWPE fabric with improved thermal resistance

A new UHMWPE-based conductive fabric was successfully prepared by radiation-induced graft polymerization and subsequent post-modification, followed by electroless deposition. The chemical structure and composition of modified UHMWPE fabrics were investigated in detail by ATR-FTIR, ²⁹Si NMR, and XPS to confirm grafting and post-modification. After electroless deposition, the morphology, thermal stability, and crystal structure of original and modified fabrics were characterized by SEM, TG, DSC and XRD. Cu-deposited UHMWPE fabric exhibited much better thermal resistance than that of UHMWPE and Cu@UHMWPE-g-PAAc. In order to improve the oxidation resistance of copper-deposited fabric, nickel was processed on copper-coated UHMWPE fabric to protect the copper layer. An electromagnetic shielding effect test showed the nickel-copper coated UHMWPE fabric could shield 94.5% of the electromagnetic wave in the frequency range of 8-12 GHz. This work provides an approach for addressing the issue of poor thermal resistance of metal-coated polymeric materials due to the inherent low melting point of the organic support.

"Raincoat for explosives": Surface chemistry approach to control wetting of nitrocellulose with nitroglycerin

HYPOTHESIS

Wicking and percolation of a liquid in porous media is, among other factors, strongly affected by wettability of the pores. Nitrocellulose (NC) fibrous matrix impregnated with nitroglycerin (NG) is a main component of propellant formulations. Over time, NG, being a wetting liquid, leaks out from the matrix causing fires and explosions resulting from the storage. Here, we propose a chemical functionalization approach aimed at preparation of lyophobic coatings of NC to control wetting and to inhibit leakage of NG.

EXPERIMENTAL

NC was functionalized by a two-step process using the reaction of 3-(triethoxysilyl-propyl) isocyanate followed by reactions with either alkyl-, fluoroalkyl-, or phenyl-silane producing NC surfaces ranging in lyophobicity. The wettability of the NC pellets was characterized using water, hexadecane, and NG as probe fluids.

FINDINGS

FTIR and chemical analysis supported the covalent attachment of organosilanes to NC via robust carbamate and siloxane bonds. SEM and DSC of the modified NC materials suggested that the bulk properties of NC were not affected by the reactions with silanes. The contact angles of the modified NC changed over a wide range demonstrating surfaces with "tunable" wetting. NC grafted with fluoroalkyl-groups showed the most NG-repelling properties (θ_Adv/θ_Rec ∼ 90°/50°): NG beaded up and did not penetrate these surfaces.

Preparação e caracterização de materiais híbridos celulose/NbOPO4.nH2O a partir de celulose branqueada de bagaço de cana-de-açúcar

Este trabalho descreve a preparação e caracterização do híbrido celulose/fosfato de nióbio hidratado (Cel/NbOPO4.nH2O) utilizando como material de partida a celulose branqueada de bagaço de cana-de-açúcar e o nióbio metálico. O híbrido foi preparado por dois métodos: denominados métodos I e II. O método I consistiu na dissolução do nióbio metálico em solução de ácido fluorídrico/nítrico (100:10), com tempo de contato de 16 horas entre a celulose branqueada do bagaço de cana-de-açúcar e a solução ácida. Adicionou-se a essa solução ácido fosfórico para precipitação do material. O método II foi semelhante, com proporções diferentes da solução ácida fluorídrico/nítrico (160/100), sem tempo de contato da celulose com a solução ácida. Os métodos I e II utilizaram as seguintes proporções de cel/ Nb2O5.nH2O: (10:10);(10:6) e (10:2). Os materiais preparados pelos métodos I e II foram caracterizados por difração de raios X (DRX), termogravimetria (TG/DTG) e microscopia eletrônica de varredura (MEV). Observou-se aumento do índice do grau de cristalinidade e mudanças na morfologia dos materiais preparados.