Catalyst development for the selective oxidation of ethoxylates to their corresponding ether carboxylic acids

The aerobic selective oxidation of polyethoxylates to their corresponding carboxylic acids was investigated using supported Au-based catalysts in aqueous alkaline solution. Introduction of Pt as secondary metal to the titania supported Au catalyst led to a significant boost in activity while maintaining total selectivity. A screening of different preparation methods and metal ratios led to a titania supported AuPt catalyst with a substantially reduced intermediate leaching of the catalytically active metals. A long-term stability study showed no noble metal loss of this particular catalyst after a set of repeated batches, but still revealed a distinct loss in activity due sintering of the metal nanoparticles. By switching from titania to ceria as support material, intermediate metal leaching could be prevented completely while maintaining total selectivity and further enhancing the activity.     

Properties and characteristics of novel formaldehyde-free wood adhesives prepared from Irvingia gabonensis and Irvingia wombolu seed kernel extracts

There is renewed interest in the domestication of Irvingia tree species due to the potential use of various parts of the tree as raw materials for a wide range of applications such as biodiesel production, cosmetics, perfumes, soap, weight-loss supplement etc. The current study investigates the properties of extracts from the seed kernels of two Irvingia species – Irvingia gabonensis (IG) and Irvingia wombolu (IW) as natural wood adhesives. Three extraction methods using various solvent/solute media were compared in terms of yield, composition and mechanical properties. Statistically, the analysis revealed significant differences between the different extraction methods. The adhesion properties of the extracts were tested on wood veneers according to the American Society for Testing and Materials standard (ASTM D – 906-64). The shear strength of the extracts ranged from 0.55 to 1.5 MPa and 0.86–1.7 MPa for IG and IW, respectively. The initial decomposition temperature of all Irvingia Kernel extract ranges from 138.3 to 149.11 °C for IG and 129.5–145.3 °C for IW. As a result, the hot melt temperature for the adhesive experiments was set around 150 °C. The results indicate that Irvingia kernel extract is a more promising source of non-formaldehyde based adhesives in wood composite production.     

“Click” reactions in polysaccharide modification

Polysaccharide chemistry is enjoying accelerating development thanks to advances in synthetic techniques, biochemistry and solvents, which enable polysaccharide materials to be useful in a variety of demanding applications. Among the synthetic advances, click chemistry has reconfigured the realm of polysaccharide modification that previously was dominated by conventional synthetic approaches such as esterification and etherification. “Click” reactions provide mild, modular, and efficient modification pathways, and equally importantly allow us to synthesize derivatives with novel functionality, architecture, and properties, that are otherwise difficult to obtain via conventional methods. Herein, we review application in polysaccharide modification of six groups of click reactions; CuAAC (copper catalyzed alkyne/azide cycloaddition), metal-free [3+2] cycloaddition, Diels–Alder reaction, oxime click, thiol-Michael reaction, and thiol-ene reaction, as well as one click-like reaction that is the subject of our own research, olefin cross-metathesis.     

Bio-renewable precursor fibers from lignin/polylactide blends for conversion to carbon fibers

Lignin, a highly aromatic biopolymer extracted as a coproduct of wood pulping, was investigated as a suitable precursor for carbon fibers. Lignin was chemically modified and blended with poly(lactic acid) (PLA) biopolymer before melt spinning into lignin fibers. The chemical modification of raw lignin involved butyration to form ester functional groups in place of polar hydroxyl (–OH) groups, which enhanced the miscibility of lignin with PLA. Fine fibers were extracted and spooled continuously from lignin/PLA blends with an overall lignin concentration of 75 wt.%. The influence of chemical modification and physical blending of lignin with PLA on the resulting fiber was studied by analyzing the microstructure of the fibers using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The influence of blend composition on the phase behavior was studied by differential scanning calorimetry (DSC). The effect of composition on the mechanical properties was studied by tensile tests of the lignin/PLA blend fibers. The thermal stability and carbon yield of the blended fibers with different concentrations of lignin were characterized by thermogravimetric analysis (TGA). The microstructure analysis of carbon fibers produced from lignin/PLA blends revealed composition dependent microporous structures inside the fine fibers.     

Durability of particleboards made from wood particles chemically modified with propionic anhydride: results after six years in ground stake-test

Propionylated particleboard stakes with 12.2% propionyl content were tested in ground contact in Western Greece. The stakes showed severe attack after five years of testing and total decay after six years, whereas the unmodified boards showed total decay during the fourth year of testing.     

Stakeholder ranking of watershed goals with the vector analytic hierarchy process: Effects of participant grouping scenarios

More effective methods of eliciting and summarizing stakeholders' goals can assist in improving watershed management. This paper discusses the process of summarizing the goals that were generated during a workshop of watershed stakeholders in Virginia by using the Vector Analytic Hierarchy Process, and then grouping them into homogeneous subgroups by using two different methods: 1) assigning subgroups based on individuals' stated affiliations from a participant bio-sheet; and 2) assigning subgroups based on the similarity of individuals' actual preferences between the goals. Several different clustering approaches are considered for creating the preference-based subgroups, and the relative advantages and disadvantages of each approach are discussed. The process of combining the subgroups to generate a single overall preference structure for the group as a whole is also considered, and the final results are compared based on both the resulting rankings and the coherence, or variability of opinion, that they reflect. Determining the “best” set of subgroups can be valuable not only in exploring the underlying nature of the population's preferences, but also in supporting additional discussion and analysis of the results. As such, it can ultimately lead to much stronger and better informed decision-making by the stakeholders.     

Nanopaper membranes from chitin–protein composite nanofibers—structure and mechanical properties

Chitin nanofibers may be of interest as a component for nanocomposites. Composite nanofibers are therefore isolated from crab shells in order to characterize structure and analyze property potential. The mechanical properties of the porous nanopaper structures are much superior to regenerated chitin membranes. The nanofiber filtration‐processing route is much more environmentally friendly than for regenerated chitin. Minerals and extractives are removed using HCl and ethanol, respectively, followed by mild NaOH treatment and mechanical homogenization to maintain chitin–protein structure in the nanofibers produced. Atomic force microscope (AFM) and scanning transmission electron microscope (STEM) reveal the structure of chitin–protein composite nanofibers. The presence of protein is confirmed by colorimetric method. Porous nanopaper membranes are prepared by simple filtration in such a way that different nanofiber volume fractions are obtained: 43%, 52%, 68%, and 78%. Moisture sorption isotherms, structural properties, and mechanical properties of membranes are measured and analyzed. The current material is environmentally friendly, the techniques employed for both individualization and membrane preparation are simple and green, and the results are of interest for development of nanomaterials and biocomposites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40121.     

Structural evolution in graphitization of nanofibers and mats from electrospun polyimide–mesophase pitch blends

The evolution of structure in multi-step thermal treatment of polyimide–mesophase pitch (PI–pitch) blend nanofiber mats obtained by an electrospinning process is described. The mats were thermally treated at a series of stages up to 3000 °C. The structural transformation of the nanofiber mats consisted of three regimes. First regime corresponds to the removal of the majority of non-carbon elements and the formation of initial residual carbon. Second regime involves slow growth of the graphitic layers and slow improvement of their stacking order. Progressive graphitization occurs in regime three when the fibers become highly graphitic. The addition of pitch was found to give rise to overall enhanced graphitic order in the PI–pitch blend nanofibers as reflected in the smaller inter-layer spacing d₀₀₂ approaching that of the perfect graphite crystal, and the larger crystal sizes, L_c and L_a, confirmed by XRD analysis, as well as the higher ratio of graphitic structure revealed by Raman spectroscopy. Development of highly localized oriented domains in these nanofibers were observed by dark field TEM. The addition of pitch led to enhancement of both electrical and thermal conductivity.     

Effects of typical soybean meal type on the properties of soybean-based adhesive

In order to effectively apply soybean meal for the preparation of water-resistant soybean-based adhesives for plywood, the effects of three typical soybean meal products, namely, low-temperature soybean meal (LM), high-temperature soybean meal (HM), and physical soybean meal (PM), on the properties of soybean-based adhesive were investigated. The results indicated that the number of reactive groups in the three soybean meals followed the order LM > HM > PM, which in turn led to various crosslinking densities when these soybean meals were crosslinked by epichlorohydrin-modified polyamide (EMPA) during the curing process. The LM soybean adhesive had 6.6% higher soaking bond strength and 16.5% higher boiling-dry-boiling bond strength than the HM soybean adhesive, and 19% higher soaking bond strength and 33% higher boiling-dry-boiling bond strength than the PM soybean adhesive, respectively. These three soybean meals could be used to prepare soybean adhesives for interior-use plywood because all plywood panels bonded with their adhesives passed a water-soaking test at 63 °C for 3 h, but only the LM soybean adhesive achieved the desired water resistance for floor-base plywood. Among the three evaluated soybean meals, LM was the most promising raw material for the preparation of soybean-based adhesive because of a greater number of reactive groups, higher crosslinking density, and superior bond strength. Plywood panel bonded with HM soybean adhesive had a water resistance lower than, but very close to, the standard required value (>0.8 MPa) for floor-base plywood.