Tg/Tm for unsubstituted polymers

Polymers under discussion can be represented by [CH₂)_nR]_p where R is CH₂, CF₂, O, S or CH = CH; and where n can vary from 0 to ∞. The copolymer, P(ethylene-alt-TFE) is also included. These polymers tend to be highly crystalline with resultant confusion about their Tg and hence their Tg/Tm values and a clarification scheme is proposed in which it is considered that each such polymer has a double glass transition, Tg(L)/f(χ_c), Tg(U) = F(χc); and a sub-glass T<Tg(L) at 0.75 Tg(L), where F(χc) signifies a function of fractional crystallinity, χ_c. T<Tg(L) and Tg(L) increase linearly with Tm. The ratio, Tg(L)/Tm, is therefore, not a constant but is close to 0.5. T<Tg(L)/Tg(L) is also not a constant but is close to 0.75. Tg(U) lies within a wedge whose top and bottom sides increase with Tm. The premelting, intracrystalline transition temperature, Tα_c, is also a linear function of Tm. It is suggested that the scheme outlined above should help to resolve uncertainties in assigning transition temperatures for unsubstituted polymers. The low Tg/Tm values for these polymers is discussed in terms of their small da/dc ratios and small crosssectional areas per chain.     

Hydrogenation of canola oil in the presence of nickel and the methyl benzoate-chrome carbonyl complex

Canola oil was hydrogenated using a mixture of homogeneous methyl benzoate-Cr(CO)₃ and heterogeneous nickel catalysts. The effect of the methyl benzoate-Cr(CO)₃_to-nickel ratio on the activity, specific isomerization index, linoleate and linolenate selectivities, and fatty acid composition was evaluated, and the results compared with those obtained with commercial nickel catalyst and methyl benzoate-Cr(CO)₃ used individually. At higher chromium-to-nickel ratios the activity of nickel was inhibited and the system behaved essentially like the pure chrome complex, while at low chromium-to-nickel ratios the characteristics of the nickel predominated. In a short transition zone relatively high reaction rates were obtained with significantly reducedtrans-isomer levels in the product. In a broader sense, it may be possible to combine a homogeneous and heterogeneous catalyst while retaining the advantages of both. We may thus be able to design catalyst systems for specific applications.     

Colloidal silica removal in coagulation processes for wastewater reuse in a high-tech industrial park.

Four experiments of coagulation and flocculation were conducted to investigate the characteristics of colloidal silica removal in a high-tech industrial wastewater treatment plant for reclamation and reuse of the effluent. Experimental results illustrated that poly-aluminium chloride (PACl) showed higher performances on colloidal silica removal than alum. Interestingly, the two coagulants demonstrated the same capacity on silica removal. The specific silica removal capacity was approximately 0.135 mg SiO2/mg Al2O3 when the dosage of coagulants was in the range 30-150 mg/L Al2O3. In addition, the silica was reduced significantly at the condition of pH above 8. Experimental data implied that precipitation of aluminium flocs was the major mechanism for colloid silica removal in PACl and alum coagulation, besides, charge adsorption was also important for improving removal efficiency. Moreover, the addition of polyacrylic acid (PAA) as a flocculant could slightly advance silica removal in the PACl coagulation. The combined PACl/PAA/flocs coagulation was effective for the removal of colloidal silica, soluble COD, and turbidity and also suitable as a pretreatment unit in wastewater reclamation and reuse processes.     

The research seminar on computer algebra in 2005–2006

An annual report on meetings of the scientific research seminar on computer algebra is presented.     

Radiographisch-densitometrische Holzeigenschaftsuntersuchungen an Douglasien aus unterschiedlich durchforsteten Versuchsflächen

From two experimental areas with different thinning grades of a mixed stand of Douglas-fir and spruce, increment cores were taken from 40 Douglas-fir trees, chosen at random in a height of 1.3 m. The properties ring width, latewood percentage, average density, maximum and minimum density were examined from one part of the material by the x-ray densitometric method. The oven-dry density of the remaining part of increment core was examined for additional control. Based on the existing sample data, a significantly higher ovendry density was determined in the untreated area of higher stand density (376 stems/acre) than for the thinned stand (214 stems/acre). The specific gravity (at 10% moisture content) determined by x-ray densitograms shows no statistically valid difference on the average. The possible factors for this result are still being discussed. Further investigations of interactions between individual properties of the Douglas-fir samples obtained by the x-ray densitometric method are being carried out by multiple linear regression analysis.     

Hydrogen peroxide: Control of its content in water objects

A brief review of existing methods designed to determine hydrogen peroxide in aqueous media has been presented. Particular attention has been given to biosensor devices enabling us to exercise simple and express control of concentration of the specified compound.     

Two geometrical isomers of linoleic acid: Improved total syntheses

The total syntheses of 9(Z),12(E)- and 9(E),12(Z)-octadecadienoic acids have been carried out. A useful intermediate in both syntheses, 8-bromo-octanoic acid, recently has become available from commercial sources. This compound has been used to expedite the preparation of these isomers. The remaining carbon atoms were derived from propargyl alcohol along with either 1-heptyne or acetylene and 1-bromopentane. Because the overall yield for each sequence was roughly 15% and there were no extraordinary reaction conditions in any of the synthetic steps, the compounds could be prepared readily in multiple gram quantities. The syntheses of the two compounds were supported by data from a variety of spectroscopic techniques.