A New Route to Highly Stretchable and Soft Inorganic–Organic Hybrid Elastomers Using Polydimethylsiloxane as Crosslinker of Epoxidized Natural Rubber

Sulfur or peroxide crosslinking is the most common and conventional method to develop elastomeric materials. A new approach to crosslink epoxidized natural rubber (ENR) by aminopropyl terminated polydimethylsiloxane (AT-PDMS) is described, intending to develop a new kind of hybrid organic–inorganic elastomers. The curing reaction is accelerated by using hydroquinone as a catalyst. The formation of the hybrid structure is evident from the appearance of two glass transition temperatures, at −1 and −120 °C, for the ENR and PDMS phases, respectively. The curing reaction is found to be of first order with respect to amine concentration with the estimated activation energy of ≈62 kJ mol⁻¹. Comparing the mechanical properties to a typical ENR-sulfur system leads to the conclusion that the ENR/AT-PDMS hybrid structure is highly stretchable and soft, as demonstrated by its relatively higher strain at failure (up to ≈630%), and lower hardness and modulus values. The higher stretchability and soft nature of the material are achieved by introducing flexible PDMS chains during the curing process resulting to a hybrid elastomer networks. This kind of soft but robust materials can find several applications in diverse fields, such as soft robotics, flexible, and stretchable electronics.     

A STUDY ON THE BEHAVIOUR OF GALLIUM IN THE IRONMAKING PROCESS

Gallium is a valuable rare metal which is mainly being used in the production of GaAs. The demand for gallium is increasing but production is limited since gallium is extracted only as a by-product of bauxite processing. On the other hand coal, ironmaking coke and iron ore gangue contain traces of gallium. However little is known about the behaviour of gallium in ironmaking. The aim of the study is to clarify the distribution of gallium between hot metal, slag and top gas by means of laboratory experiments. It was found that Ga2O3 is not stable in blast furnace slags and that gallium is retained in hot metal. Vacuum distillation experiments with hot metal showed that gallium is not transferred to the gas phase. Data on the input and output of gallium at two industrial blast furnaces, as well as chemical analyses of the gallium content of several cokes are presented, too.     

Paraffin oil solutions of the mixture of sorbitan monolaurate-ethoxylated sorbitan monolaurate as lubricants

Paraffin mixtures of sorbitan monolaurate (SML)-ethoxylated sorbitan monolaurate (ESML) were applied as lubricant additives. The esters tested can be obtained from natural resources. They are environment-friendly. Tests under steady load conditions were performed to assess their tribological properties. The friction coefficient and wear scar diameter were measured. On the basis of the results obtained one can conclude that the mixtures tested significantly reduce motion resistance and wear. As compared to paraffin oil, wear scar diameter was reduced four times, while friction coefficient—even six times. The influence of total concentration and SML:ESML ratio on tribological properties was analyzed. The synergistic effect, attaining its optimum for comparable mole fraction of both esters, was observed. The results can be interpreted in terms of creation of micellar solutions and interaction of these structures with friction surface.     

Weiterentwicklung einer Methode zur Bienenbruthaltung unter Laborbedingungen

In the LAVES Institute for Apiculture honey bee brood has been reared in the laboratory according to the method of Aupinel et al. (Bull Insectol 58:107?C111, 2005) for studies on the effects of plant protection products as well as for further improvement of the method since 2008. The introduced methodological changes have a positive effect on the number of larvae available for experimental purposes. Furthermore, the treatment with MBC-solution (methyl-benzethonium chloride) could be replaced by pasteurization, which is to be viewed positively from a health perspective for the personnel but also in terms of possible synergistic effects with active ingredients.     

Degradation of natural polyphenols by methanogenic consortia enriched from digested municipal sludge.

Using digested municipal sludge as the inoculum and either rutin, quercetin or hesperidin as the sole external carbon source. methanogenic consortia were enriched which converted various flavonoids at initial concentration of 0.5 3.0mM during stationary incubation at 37 degrees C in serum bottles with specific rates ranging from 0.025 to 0.073 micromol min(-1) (mg protein)(-1). In the culture fluid, several hydroxyaromatic metabolites as well as VFA (acetate, propionate, n-butyrate) were detected and biogas was formed in the headspace of the test bottles. Most of these metabolites were identified. Based on their sequential appearance/disappearance in the test cultures it was concluded that following initial hydrolysis of the glycosidic bond by cellular enzymes, ring C of the flavane skeleton was hydrolytically cleaved yielding an A- and B-ring fission product. In case of the flavonol quercetin, phloroglucinol (A-ring) and 3,4-dihydroxyphenylacetate (B-ring) were identified as the fission products whereas the flavanone hesperetin was cleaved with formation of phloroglucinol (A-ring) and 3,4-dihydroxyphenylpropionate (B-ring). In pre-adapted subcultures amended with either hesperidin or hesperetin, all of the formed hydroxyaromatic metabolites disappeared within 100 h of incubation whereas in the culture medium of rutin and quercetin degrading consortia m-cresol (3-methylphenol) was formed as the ultimate hydroxyaromatic metabolite being detectable in considerable amounts even after prolonged incubation.     

Morphology and electrical resistivity of melt mixed blends of polyethylene and carbon nanotube filled polycarbonate

Blends were prepared from a high density polyethylene (PE) material and a conductive polycarbonate (PC) composite containing multiwalled carbon nanotubes (MWNT). The PC composite contained 2 wt% MWNT and was prepared by diluting a PC masterbatch consisting of 15 wt% MWNT by melt mixing in an extruder. The aim of blending a conductive PC composite with PE was to obtain a conductive blend at lower amounts of MWNT than required for the pure PC component. The blend morphology was found to be co-continuous over a broad composition range of 30–80 vol.% of the filled PC phase as verified by selective extraction of PC and morphological investigations. The co-continuous structure is very fine with ligaments in the range of 1 μm. Significantly reduced volume resistivity values, i.e. in the range of 10⁷ Ω cm, could be achieved in the same composition range of that of the continuous PC phase, i.e. starting at compositions of 30 vol.% filled PC. Here, the total MWNT content in the blend was only 0.41 vol.%. Interestingly, even if the MWNT had been incorporated in the PC phase, the tubes are still visible in the blends after selective extraction of PC. Scanning electron microscopy investigations revealed that the MWNT bridge the PC and PE phases, at least with their ends. This can be understood by the length dimensions of the tubes, which is higher than the phase sizes in the blends.     

Fluidization characteristics and charging behavior of fly ash in a vibro-fluidized bed

Fluidization characteristics of fly ash were investigated in a fluidized bed subjected to mechanical vibrations. In the presence of mechanical vibrations, the minimum fluidization velocity decreased from 4.0 to 1.0 mm/s, and the pressure drop increased slightly. The charge-to-mass ratios of fly ash along the fluidized column revealed that charging behavior of fly ash in the freeboard region significantly differed from that in the dense bed region. In the dense bed region, the net charges of fly ash were slightly negative or almost neutral, whereas fly ash in the freeboard region tended to carry positive charges. Loss-on-ignition (LOI) of fly ash was examined in different regions of the fluidized bed, and the results showed that LOI varied considerably inside the column, generally being lower in the freeboard than in the dense bed since finer particles were entrained into the freeboard. In the dense bed, particle–wall collisions resulted in positively charged carbon and negatively charged ash particles, whereas carbon particles in the freeboard region tended to carry negative charges. The findings demonstrate the potential for separating unburned carbon from fly ash by utilizing a vibro-fluidized bed as a tribocharger.     

Conclusions on the development of smelting reduction

The present paper summarizes the results of the US-German Symposium on “Innovative Iron and Steel Making Processes”. A survey is given on the state-of-the-art technology as well as the state and further needs of research.