The effect of cellulose–solvent interaction on the mechanical properties of bonded fibrous structures

The mechanical properties, i.e., the tensile strength, tensile modulus, elongation at rupture, and tensile energy absorption (work of rupture), of a dry-formed network of cellulose fibers are shown to be substantially improved by impregnation of the network with organic solutions of poly(vinyl acetate) (PVAC). With the exception of the tensile strength, the improvement of the mechanical properties in the dry state is, however, dependent not only on the polymer content, but also on the interaction between the solvent and the cellulose fibers constituting the network. A solvent which interacts strongly with cellulose produces a stiffer and less ductile network than a more inert liquid. It is suggested that this effect is the result of a change in the cellulose network structure itself. The solvents used in this study were methanol, acetone, ethyl acetate, chloroform, and toluene.     

Internal stresses in cold-drawn and irradiated polyethylene

The influence of high-energy radiation on the internal stress level in cold-drawn, high- and low-density polyethylene, with and without subsequent annealing, has been determined using a stress relaxation method described earlier. The internal stress level (σ _i) is found to increase substantially with the radiation dose for doses below 40 Mrad, while the increase at higher doses is only moderate. It is suggested that the initial increase is due to a preferred cross-linking of the amorphous phase or the fold surface of the lamellae. An exception to this behaviour was observed for cold-drawn low-density polyethylene, where the internal stress decreased as the radiation dose was raised.     

Design of Hygroscopic Bioplastic Products Stable in Varying Humidities

Hygroscopic biopolymers like proteins and polysaccharides suffer from humidity-dependent mechanical properties. Because humidity can vary significantly over the year, or even within a day, these polymers will not generally have stable properties during their lifetimes. On wheat gluten, a model highly hygroscopic biopolymer material, it is observed that larger/thicker samples can be significantly more mechanically stable than thinner samples. It is shown here that this is due to slow water diffusion, which, in turn, is due to the rigid polymer structure caused by the double-bond character of the peptide bond, the many bulky peptide side groups, and the hydrogen bond network. More than a year is required to reach complete moisture saturation (≈10 wt.%) in a 1 cm thick plate of glycerol-plasticized wheat gluten, whereas this process takes only one day for a 0.5 mm thick plate. The overall moisture uptake is also retarded by swelling-induced mechanical effects. Hence, hygroscopic biopolymers are better suited for larger/thicker products, where the moisture-induced changes in mechanical properties are smeared out over time, to the extent that the product remains sufficiently tough over climate changes, for example, throughout the course of a year.     

Adsorption of trace elements on pyrite surfaces in sulfidic mine tailings from Kristineberg (Sweden) a few years after remediation

Bioaccumulation of Cd, Co, Cu, Ni, Pb and Zn in the Antarctic calanoid copepod Metridia gerlachei (Giesbrecht 1902) was investigated during a cruise of RV 'Polarstern' to the Weddell Sea, primarily to provide information on accumulation strategies for the metals tested. With the sole exception of Cd, the copepod accumulated metals during exposure and depurated them in uncontaminated seawater. The process of uptake and depuration was successfully described by a hyperbolic model, leading to significant estimations of the following experimental bioconcentration factors (BCFs): 210 (Co), 3430 (Cu), 3060 (Ni), 670 (Pb) and 2090 (Zn). Furthermore, we provide an approach to evaluate the sensitivity of Metridia gerlachei as a biomonitor of water-borne metals in the field; the results indicate minimal increments in ambient exposure concentrations of: 0.5 microg Cu l(-1), 0.8 microg Ni l(-1), 0.6 microg Pb l(-1) and 0.2 microg Zn l(-1), suggesting a high sensitivity of M. gerlachei for biomonitoring.     

Frames,agency and institutional change: the case of benchmarking in Danish construction

This study examines change and the sources influencing the formulation and diffusion of policies in construction. The change examined is the introduction of a benchmarking policy initiative in the Danish construction industry. Using institutional theory with emphasis on the concepts of frames and framings, we show how strategically motivated actors are able to frame policy problems in ways that disclose the mixture of motives, interests and institutional mechanisms at play in change processes. In doing so, we contribute to the literature on the role of agency in institutional change and the framing of policy problems. We conclude by highlighting how insights gained from the framing perspective present a challenge to the dominant comprehensive rationalist view of the policy process and the formulation and implementation of reform initiatives.     

Application of double focusing sector field ICP-MS for multielemental characterization of human hair and nails. Part III. Direct analysis by laser ablation

The capabilities of laser ablation double focusing sector field inductively coupled plasma mass spectrometry for the determination of 55 elements in nails and hair were studied. Quantification was performed by external calibration using in-house matrix-matched standards in tablet form following correction for variations in ablation efficiency by internal standardization using a matrix element (S). For nails, intra-individual long- and short-term chronological variations as well as depth distribution patterns were studied. For the majority of elements tested, significant enrichment was found in the surface of the nail. Element distributions along a hair strand were investigated with a spatial resolution of 2.5 mm.     

Self-diffusion of oil in lubricating greases by NMR

Self-diffusion of base oil in six model lubricating greases and in the base oils themselves was measured using pulsed-field gradient nucleic magnetic resonance (NMR) at 23, 40, 70, and 90°C. Three of the greases were based on naphthenic mineral oils, and three were based on synthetic polyalphaolefin oils. Soaps of 12-hydroxy stearic acid were used as thickener agents in all six greases. The purpose of the investigation using NMR was to see if structure varies with temperature, and if NMR is a viable method for structure determination. The ratio between the diffusion coefficient of the base oil in the grease and the neat base oil in itself was evaluated as a function of temperature. This ratio was taken as a direct indicator of the obstruction effect that the thickener has on the oil. The thickener showed a stronger obstruction effect on the base oil in the synthetic grease than in the mineral-based grease. This was related to the soap content, which, for these greases, is roughly twice as high in the synthetic greases as in the mineral ones. The obstruction effect was constant in the temperature range 40–90°C for mineral- as well as synthetic-based greases. NMR was judged to be a promising method for investigating how the gellant affects the diffusion coefficient of oil in a lubricating grease.