Thermooxidative reactions of polypropylene wax in the molten state

Thermooxidation of polypropylene wax was investigated in the molten state under an air‐flowing atmosphere. Calorimetric measurements were performed to investigate the effect of the inclusion of 1‐dodecanol as an efficient primary alcohol and to reveal the typical outlines of thermooxidation, that is, the induction time and oxidation rate. The same parameters were obtained and compared on the basis of the Fourier transform infrared (FTIR) peaks of major oxidation products, such as ketones and hydroxyl groups. The results showed that 1‐dodecanol caused a change in the shape of the calorimetric thermogram and also yielded oxidized products with more clarity in color. With the Arrhenius equation, the apparent activation energy was calculated on the basis of the induction time and oxidation rate for carbonyl and hydroxyl groups individually. The obtained apparent activation energy was in agreement with the proposed mechanism based on bimolecular hydroperoxide decomposition involving dodecanol. With FTIR spectroscopy, no changes in the chain helical conformation or double‐bond concentration were observed during oxidation up to 500 min. An acid value of up to 6 mg of KOH per gram was obtained at this time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Subquarter-micrometre elevated source-and-drain MOSFET structureusing polysilicon spacers

A novel subquarter-micrometre MOSFET with a selfaligned source and drain structure is proposed with elevated sources and drains formed by using polysilicon spacers. The spacers can reduce the effective channel length by 50% compared to the mask length, and reduce the junction capacitance by over 30% through a reduction in junction area, as shown by PISCES simulations. A graded oxide spacer is used to decrease the parasitic gate-to-drain capacitance     

Viscoelastic behavior of NBR/phenolic compounds

NBR/phenolic interpenetrating networks (IPNs) offer a wide variety of mechanical and physical properties at moderately high temperature. This temperature stability along with oil and fuel resistance property has made IPNs appropriate candidates for various applications. In the present work, NBR compounds containing 5, 7 and 12 phr of Novolac, as a curable phenolic resin was formulated using a two-roll mill. Low and high acrylonitrile NBR; KNB 35L and Europrene N4560 were selected in the compound and the same condition of mixing was applied in the blend preparation stage. Curing test, followed by a cooling period and the stress relaxation test were carried out consecutively and automatically in a rubber process analyzer. The samples presented various relaxation times. The relaxation curves were well estimated by Maxwell model and the Prony coefficients were determined. Furthermore, compression test was performed on the samples, so that the set or permanent deformation of each sample was measured. The results of both tests have indicated that by adding phenolic resin into the NBR matrices, the viscoelastic behavior of the compounds become more elastic, to the detriment of the viscous component. This phenomenon would be due to IPN formation in the compounds. In addition, by increasing the phenolic resin content in the compounds, the difference between maximum and minimum torque (M _H ? M _L) value became greater, which is an indicator of higher cross-link density and IPN formation. Swelling test results confirmed more extensive cross-links in the compounds by addition of more resin into the compound.     

Investigating changes in electrochemical properties when nano-silica is incorporated into an acrylic-based polyurethane clearcoat

Two different types of nano-silica (i.e., hydrophilic Aerosil 200 and hydrophobic Aerosil R805) were employed in the preparation of 2-pack acrylic polyol polyurethane nano-coatings so that the electrochemical properties of the resultant coatings could be investigated. Electrochemical impedance spectroscopy was used to evaluate the corrosion performances of such nano-coatings applied onto mild steel substrates that were immersed in 3.5% (w/w) NaCl solutions. It was observed coatings that contained nano-silica increased the barrier properties of the binder, as well as the coatings’ electrochemical resistance compared with pure polyurethane coatings. The surface tension of pure polyurethane was measured by a tensiometer. Rheological properties were also determined at various shear rates by a rotaviscometer. Results showed that the surface tension of hydrophobic nano-silica is very close to the pure polyurethane matrix, giving the better compatibility of the two. This was further confirmed by transmission electron microscopy and by the fact that the hydrophobically filled nano-silica coatings showed shear thinning behavior in the fluid state. Also observed was better corrosion performance of the resultant hydrophobic nano-coatings compared to coatings embedded with hydrophilic nano-silica.