Copolymerization of norbornene with norbornene terminated polystyrene macromonomer in the presence of Ni-based/MAO catalytic systems

Copolymerization of -norbornenyl polystyrene macromonomer (NBE-PS) with norbornene (NBE) using Ni-based catalysts in combination with methylaluminoxane (MAO) was investigated. The nature of the catalyst, the of the polystyrene macromonomer as well as the [NBE-PS]/[NBE] ratio have been shown to be important parameters to obtain graft copolymers with high NBE-PS incorporation (up to 43 wt%). The compatibilization ability of these graft copolymers has been checked for PS/PNBE blends. The length of the grafts was proved not to be an important parameter to consider compatibilization of the PS/PNBE blend.     

A Flavanone and Two Phenolic Acids from Chrysanthemum morifolium with Phytotoxic and Insect Growth Regulating Activity

Leaves of Chrysanthemum morifolium cv. Ramat were extracted sequentially with hexane, ethyl acetate, and methanol. The methanol fraction, when incorporated into artificial diet was found to reduce the growth of cabbage looper (Trichoplusia ni Hubner) larvae at concentrations between 500 and 5000 ppm of diet. Fractionation of the methanol extract on a Sephadex column yielded five fractions, three of which reduced the weight of larvae relative to the control. One fraction was analyzed using high performance liquid chromatography (HPLC) and found to contain three main constituents. These compounds were purified using a combination of gel permeation chromatography on Sephadex LH20 and HPLC, and analyzed by 1H and 13CNMR as well as undergoing chemical and physical analyses. The compounds were identified as: 1, chlorogenic acid (5-O-caffeoylquinic acid); 2, 3,5-O-dicaffeoylquinic acid; and 3, 3', 4',5-trihydroxyflavanone7-O-glucuronide (eriodictyol7-O-glucuronide). At concentrations between 100 to 1000 ppm these compounds reduced both growth and photosynthesis of Lemna gibba L. with the order of efficacy being: flavanone > chlorogenic acid > 3,5-O-dicaffeoylquinic acid. Furthermore, when incorporated separately into artificial diet these compounds, at 10 to 1000 ppm, enhanced or reduced growth of the cabbage looper (Trichoplusia ni) and gypsy moth (Lymantria dispar L.).     

Injection molding shrinkage of PP: Experimental progress

Injection molding shrinkage deals with dimensional differences between a molded part and the cavity. By adding an array of orthogonal marks into a mold, local shrinkage values may be obtained by comparing dimensions of this array with dimensions of the array replicated on the surface of the parts. A profilograph is employed to obtain dimensional measurements, in the parallel to flow direction and in the cross flow direction. A sensitivity analysis is conducted to determine aspects of shrinkage evaluation causing uncertainty on the results. Prominent sources of uncertainty found are mark straightness defect and part warpage. Uncertainty on shrinkage is evaluated to 0.00025 mm/mm for a distance between the marks of 6.350 mm. Shrinkages have been evaluated locally for molded plates. Different distribution forms were observed for parallel to flow and cross flow shrinkage. Important anisotropy is also observed. The effects of holding pressure and injection velocity on shrinkages have been evaluated using a 2³ factorial design of experiment for three locations on the plates. Finally, shrinkages for three mold geometries have been compared: constant thickness plate, variable in thickness symmetrical plate, and variable in thickness asymmetrical plate. Variable in thickness plates showed the importance of solidification dynamics on final shrinkages. POLYM. ENG. SCI., 46:1275–1283, 2006. © 2006 Society of Plastics Engineers     

Study of the telomerization of dimethylaminoethyl methacrylate (DMAEMA) with mercaptoethanol. Application to the synthesis of a new macromonomer

The telomerization of dimethylaminoethyl methacrylate (DMAEMA) with mercaptoethanol initiated by 2,2′-azobisisobutyronitrile was first investigated at 70 °C and the influence of the type of solvent was studied. The results showed that well-defined telomers of DMAEMA could not be synthetized via telomerization of DMAEMA in water or water/acetonitrile mixture since the telomerization reaction is in competition with the nucleophilic addition of thiol onto the monomer. Transfer constants for mercaptoethanol in benzene and acetonitrile were determined by Mayo's and O'Brien's methods. The transfer constant obtained in acetonitrile (0,6) was higher than that obtained in benzene. This difference can be explained by the fact that the thiol was consumed by two reactions: nucleophilic addition and telomerization. The influence of solvents on the polymerization kinetics was enlightened. These results were applied to the synthesis of macromonomers of DMAEMA with isocyanatoethyl methacrylate (IEM). These macromonomers were copolymerized with styrene.     

Synthesis and characterization of long-chain fatty acid cellulose ester (FACE)

Long-chain fatty acid cellulose esters (FACE) were synthesized by the acid chloride-pyridine reaction with different degrees of substitution (DS). The hydrolyzed soybean oil was used as unsaturated fatty acids, its unsaturation degree, and composition were analyzed by ¹H and ¹³C NMR methods. The chemical structures of FACE were confirmed by solid-state ¹³C NMR, and substitution reaction of fatty acid chloride on cellulose were analyzed by IR spectroscopy. FACE(s) are insoluble in common organic solvents, such as benzene, toluene, THF, etc., at refluxing temperature. As the DS increased, the tensile strength of extruded FACE films decreased, but elongation increased. © 1994 John Wiley & Sons, Inc.     

Biochemical,functional, and histochemical effects of essential fatty acid deficiency in rat kidney

The present study was designed to examine the effects of EFA deficiency (EFAD) on biochemical, functional, and structural aspects of the kidney in growing and adult rats fed a normal or EFAD diet for 9 wk after weaning. Food and fluid intake (FI), urine volume, and Na⁺ and K⁺ excretions were measured weekly from weeks 4 to 8 by placing the rats in individual metabolic cages for 24 h. At week 9, Li⁺ and a 5% water load, respectively, were administered at 14 and 1.5 h prior to glomerular and proximal tubular function studies, as assessed by 3-h creatinine (C_Cr) and Li⁺ (C_Li+) clearances. Hematocrit and urine volume; serum and urine [Cr], [Li⁺], [Na⁺], and [K⁺]; and renal FA distribution were also measured. Data [corrected to 100 g/body weight (bw) and presented as means ±SEM] were significant, at P<-0.05. Despite a similar ingestion of solids from weeks 4 to 7 (weeks 7 to 10 of life), the rats on the EFAD diet showed a decreased body weight from week 5. From weeks 4 to 8, Fl and urine volume were similar for both groups, but the Fl increased at week 6 in the EFAD group; 24-h Na⁺ and K⁺ excretions were similar at all weeks, except for an increase in the EFAD group for both ions at week 7. In the EFAD group, C_Cr and C_Li+ decreased by 27 and 56.3%, respectively (385.7±33.4 vs. 280±21.1, and 21.0±2.1 vs. 9.2±1.1 μL/min/100 g; n=9 vs. 10), the latter result suggesting increased proximal reabsorption. The 3-h Na⁺ and K⁺ excretions were similar, but the Li⁺ decreased (0.78±0.06×10⁻² vs. 0.32±0.03×10⁻² μeq/min/100 g) in the EFAD group, giving additional support to the suggestion. Renal structure was normal and similar for both groups, but the EFAD group showed a more prominent proximal tubule brush border, together with heavier periodic acid-Schiff staining in all specimens from weeks 5 to 9. In the EFAD group, FA of the n−9 and n−7 series were higher, but most of the n−6 series were lower as a percentage of total lipids in the medulla and cortex. Medullary levels of 20∶4n−6 were maintained, 22∶4n−6 declined twice, arachidonic acid was maintained, and 20∶5n−3 was lower. The EFAD diet affected glomerular function, proximal tubular structure and function, and FA distribution in the rat kidney.     

Zinc-rich powder coatings corrosion in sea water: influence of conductive pigments

The effect of addition of conductive pigments like carbon blacks on the corrosion behavior of zinc-rich powder paints coated steel in artificial sea water was investigated. Open circuit potential measurements were used to characterize the cathodic protection ability and duration. Micro-Raman spectroscopy analysis was performed in order to identify the corrosion products and to follow the penetration of the solution inside the coatings.

Two different effects were pointed out: an increase of the porosity induced by carbon addition and a galvanic action between zinc and carbon pigments. The performance of the powder coatings, strongly improved if the carbon amount is sufficient, was compared to the one reported for solvent-based zinc-rich paints.     

Kinetics of the selective catalytic reduction of NO by NH3 on a Cu-faujasite catalyst

The kinetics of the selective catalytic reduction (SCR) of NO by NH₃ in the presence of O₂ has been studied on a 5.5% Cu-faujasite (Cu-FAU) catalyst. Cu-FAU was composed of cationic and oxocationic Cu species. The SCR was studied in a gas phase-flowing reactor operating at atmospheric pressure. The reaction conditions explored were: 458<T_R<513 K, 2503 (ppm) < 4000, 12 (%) < 4. The kinetic orders were 0.8–1 with respect to NO, 0.5–1 with respect to O₂, and essentially 0 with respect to NH₃. Based on these kinetic partial orders of reactions and elementary chemistry, a wide variety of mechanisms were explored, and different rate laws were derived. The best fit between the measured and calculated rates for the SCR of NO by NH₃ was obtained with a rate law derived from a redox Mars and van Krevelen mechanism. The catalytic cycle is described by a sequence of three reactions: (i) Cu^I is oxidized by O₂ to “Cu^II-oxo”, (ii) “Cu^II-oxo” reacts with NO to yield “Cu^II-N_xO_y”, and (iii) finally “Cu^II-N_xO_y” is reduced by NH₃ to give N₂, H₂O, and the regeneration of Cu^I (closing of the catalytic cycle). The rate constants of the three steps have been determined at 458, 483, and 513 K. It is shown that Cu^I or “Cu^II-oxo” species constitute the rate-determining active center.     

Electrochemical behaviour of copper in neutral aerated chloride solution. I. Steady-state investigation

The electrochemical behaviour of a Cu rotating disc electrode in neutral aerated NaCl solution was investigated in the cathodic and anodic ranges and at the corrosion potential. In the cathodic range, where the reduction of oxygen takes place, reduction peaks allow the identification and quantitative evaluation of insoluble corrosion products (CuCl and Cu₂O). In the anodic range Cu is dissolved, most likely as CuCl ₂ ^– . A new mechanism for the anodic dissolution is proposed after comparing our data with previously published mechanisms. Corrosion currents were found to decrease with time and to be a function of the rotation rate of the electrode. Both the mixed kinetics of the anodic partial reaction and diffusion through a porous layer seem to be relevant in controllingl _corr.     

Copper diffusion into silicon substrates through TaN and Ta/TaN multilayer barriers

A study of copper (Cu) diffusion into silicon substrates through Ta nitride (TaN) and tantalum (Ta/TaN) layers was investigated based on an experimental approach. TaN _x and Ta/TaN _x thin films were deposited by radiofrequency sputtering under argon (Ar) and Ar-nitrogen (N) plasma. The influence of the N₂ partial pressure on the microstructure and the electrical properties is reported. X-ray diffraction patterns showed that the increase of the N₂ partial pressure, from 2 to 10.7%, induces a change in the composition of the δTaN phase, from TaN to TaN_1.13, as well as an evolution of the dominant crystallographic orientation. This composition change is related to a drastic increase of the electrical resistivity over a N₂ partial pressure of 7.3%. The efficiency of TaN layers and Ta/TaN multilayer diffusion barriers was investigated after annealing at temperatures between 600 and 900 °C in vacuum. Secondary ion mass spectrometry profiles showed that Cu diffuses from the surface layer through the TaN barrier from 600 °C. Cu diffusion mechanisms are modified in the presence of a Ta sublayer. This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was held during TMS 2006, the 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized by Yongho Sohn of the University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University.