Tannin-based adhesive cross-linked by furfuryl alcohol-glyoxal and epoxy resins

To prepare a natural tannin-based adhesive with good water resistance, an environment friendly furfuryl alcohol-glyoxal resin (FG) synthesized in the laboratory was developed as a cross-linker for tannin-based adhesives. ¹³C Nuclear Magnetic Resonance (NMR) and Matrix-Assisted Laser Desorption-Ionization Time-of-Flight (MALDI-TOF) mass spectroscopy results indicated that furfuryl alcohol and glyoxal reacted under acidic conditions and that the -CH-(OH)- groups could be shown to be the ones involved in the cross-linking of the tannin-furfuryl-glyoxal adhesive (TFG). The results for the wet shear strength of TFG-bonded plywood showed that the cured TFG was improved and better than that bonded with a tannin-furfuryl alcohol (TF) adhesive. Moreover, the TFG adhesive cross-linked with 12% epoxy resin (EPR) presented a good water resistance. It had a modulus of elasticity (MOE) higher than that of tannin-furfuryl alcohol-formaldehyde (TFF), TF and phenol-formaldehyde (PF) adhesives.     

Tungsten phosphide nanosheets seamlessly grown on tungsten foils toward efficient hydrogen evolution reaction in basic and acidic media

Exploring earth-abundant electrocatalyst with active and stable hydrogen evolution reaction (HER) properties is desirable but still challengeable. Herein, WP₂ nanosheets are seamlessly grown on W foil (WP₂ NSs/W) through phosphorization of WO₃/W. This seamless WP₂/W structure is beneficial to reducing the resistance between WP₂ and W. Along with the exposed large density of active sites, WP₂ NSs/W displays outstanding HER activity with a lower onset potential of about 0 V, a smaller overpotential of 90 mV for the current density of 10 mA/cm² in basic media. Notably, WP₂ NSs/W electrode also catalyzes HER efficiently in acid. The synthesis of WP₂ NSs/W provides us a straightforward strategy to gain more cost-effective cathode for HER.     

Aramid fibers reinforced silica aerogel composites with low thermal conductivity and improved mechanical performance

Aramid fibers reinforced silica aerogel composites (AF/aerogels) for thermal insulation were prepared successfully under ambient pressure drying. The microstructure showed that the aramid fibers were inlaid in the aerogel matrix, acting as the supporting skeletons, to strengthen the aerogel matrix. FTIR revealed AF/aerogels was physical combination between aramid fibers and aerogel matrix without chemical bonds. The as prepared AF/aerogels possessed extremely low thermal conductivity of 0.0227 ± 0.0007 W m⁻¹ K⁻¹ with the fiber content ranging from 1.5% to 6.6%. Due to the softness, low density and remarkable mechanical strength of aramid fibers and the layered structure of the fiber distribution, the AF/aerogels presented nice elasticity and flexibility. TG–DSC indicated the thermal stability reaching approximately 290 °C, can meet the general usage conditions, which was mainly depended on the pure silica aerogels. From mentioned above, AF/aerogels present huge application prospects in heat preservation field, especially in piping insulation.     

Inclusion of human operator interaction in performance optimization of power distribution operations using knowledge-based methods

Conventional approaches for performance optimization of power distribution operations based solely on numerical methods do not employ the input of human operators in the decision making process. Knowledge-based methods, particularly those employing fuzzy logic, can be effectively used to obtain information from a human operator. A method is described for inclusion of human operator interaction in performance optimization of power distribution operations. The decision maker identifies system dependent parameters, defines operational policy, and offers a qualitative assessment of temperature. Fuzzy sets are used to model the temperature assessment provided by the operator. For each type of decision maker input, the paper describes the information required and how this information is used in performance optimization of power distribution operations.     

Improved performance of dye-sensitized solar cells with surface-treated TiO2 as a photoelectrode

We report on the effects of surface-modified TiO₂ on the performance of dye-sensitized solar cells (DSSCs). TiO₂ surface was modified with Na₂CO₃ via a simple dip coating process and the modified TiO₂ was applied to photoelectrodes of DSSCs. By dipping of TiO₂ layer into aqueous Na₂CO₃ solution, the DSSC showed a power conversion efficiency of 9.98%, compared to that (7.75%) of the reference device without surface treatment. The UV–vis absorption spectra, the impedance spectra and the dark current studies revealed that the increase of all parameters was attributed to the enhanced dye adsorption, the prolonged electron lifetime and the reduced interfacial resistance.     

Combined effect of aminoacids and microbial transglutaminase on gelation of low salt surimi content under high pressure processing

The paper examines the effect of High Pressure Processing (HPP) (300 MPa), the incorporation of microbial transglutaminase (MTGase) and the addition of different additives such as lysine and cystine, as potential enhancers of low-salt (0.3%) surimi gel. Effects on myosin as the molecule responsible for gelation was monitored by Fourier transform infrared spectroscopy, Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), and dynamic rheometry measurements. The effects on physicochemical properties of surimi gels were determined by Folding and Puncture tests and water holding capacity.Results indicated an increase in β-sheet when HPP was applied or additives added (cystine and lysine), especially when samples are treated with MTGase. Protein aggregation due to HPP and the additives resulted in lower myosin heavy chain (MHC) band density in the SDS–PAGE. Rheometry measurements indicated that MTGase activity was prompted by the incorporation of cystine and lysine in the absence of HPP. Also, HPP assisted gelation, resulting in improved mechanical properties of the gels. Samples containing additives, with or without HPP, exhibited the highest Folding test scores, indicating greater network flexibility. Lastly, water binding capacity was also enhanced by both additives and HPP.Industrial relevanceThe industrial relevance of the present work is focused on the appropriated gelation of myofibrillar proteins which is an essential step in the elaboration of surimi-based products. Sodium chloride has an important role in that fact inducing protein unfolding and solubilization. The reduction in NaCl content, following the NAOS strategy, required the application of different technologies to facilitate surimi adequate gelation. High-pressure processing has been commonly used as an innovative technology to prolong shelf life but it can be successfully used to induce proteins gelation. Due to that ability, the use of high pressure on surimi-based products result an interesting tool to facilitate surimi gelation. The use of Microbial transglutaminase (MTGase) alone or in combination with some aminoacids such as lysine and cystine can significantly improve surimi gelation added in a very small proportion.     

Soybean oil-based thermosets with N-vinyl-2-pyrrolidone as crosslinking agent for hemp fiber composites

Soybean oil-based thermosets from acrylated epoxidized soybean oil (AESO) with a highly reactive vinyl monomer, N-vinyl-2-pyrrolidone (NVP), as crosslinking agent to replace styrene (St) were formulated for the fabrication of hemp fiber composites. The theoretical miscibility of NVP–AESO and St–AESO systems were discussed based on the group contribution method. The AESO resin with 30 wt% NVP exhibited a slightly higher viscosity than the counterpart with St, while the maximum curing temperature of the former was considerably lower than that of the latter. The composites from 20 wt% NVP resin gained comparable mechanical properties and higher glass transition temperature (T_g) to the composites with 30 wt% St. Further increase in NVP usage to 40 wt% resulted in the composites with higher tensile strength, tensile modulus, flexural strength, flexural modulus, storage modulus, and T_g of 29.6%, 22.4%, 22.5%, 20.6%, 21.6%, and 47.2%, respectively, when compared to those of the St-based composites.     

Mechanochemical fabrication of geopolymer composites based on the reinforcement effect of microfibrillated cellulose

In this study, microfibrillated cellulose-reinforced geopolymer organic/inorganic hybrid materials, were prepared via a simple green mechanochemical method. The interaction between microfibrillated nanocellulose and geopolymer was further investigated by molecular dynamics simulation. The study established that mechanical ball milling could effectively promote the microfibrillation of bamboo pulp fibers to form reinforced geopolymer composites with a uniformly distributed cellulose skeleton network. The compressive strength of geopolymer blended with 2% microfibrillated cellulose was shown to be 85.1% higher than that of the pristine geopolymer after 30 days. In addition, the hybrid system was found to maintain excellent thermal stability due to the effective protection of the biomass components by the inorganic matrix. This one-step mechanochemical process provided an efficient approach for preparing geopolymer composites, which offers significant application potential for use in road repairs, high-temperature-resistant materials, and additive manufacturing via 3D printing.     

Effect of fiber modification with a novel compatibilizer on the mechanical properties and water absorption of hemp‐fiber‐reinforced unsaturated polyester composites

Hemp‐fiber‐reinforced unsaturated polyester (UPE) composites were prepared by compression molding. The treatment of hemp fibers with N‐methylol acrylamide (NMA) and sulfuric acid as a catalyst significantly increased tensile strength, flexural modulus of rupture and flexural modulus of elasticity, and water resistance of the resulting hemp–UPE composites. Fourier transform infrared (FTIR) spectra revealed that some NMA was covalently bonded to hemp fibers. Scanning electronic microscopy graphs of the fractured hemp–UPE composites revealed that treatment of hemp fibers with NMA greatly improved the interfacial adhesion between hemp fibers and UPE. The chemical reactions between hemp fibers and NMA as well as the mechanism of improving the interfacial adhesion were proposed and discussed. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers