Preparation and characterization of blends of high density polyethylene and poly(ethylene‐co‐1‐octene) elastomer

Mechanical, thermal, and morphological properties of blends of high density polyethylene and poly(ethylene‐co‐1‐octene) (PEO) were evaluated. The blends were prepared in a single screw extruder at 230°C and 50 rpm with volume fraction of elastomer varying in the range from 0.05 to 0.8. Factors such as chemical similarity and melt viscosity favor the interdiffusion process of phases, resulting in better interfacial adhesion. A synergistic effect on the strength at break and elongation at break for a particular range of blend composition was observed. Blends with a volume fraction of PEO higher than 5% presented a super tough behavior at room temperature. Thermal analysis showed that there is a certain degree of interaction between high density polyethylene and PEO. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1991–1995, 2001     

Effects of polymer solvents on the performance of cellulose acetate membranes in methanol/methyl tertiary butyl ether separation

The performances of cellulose acetate membranes prepared with casting solutions, with acetone, dimethylformamide (DMF), and N‐methylpyrrolidone (NMP) as solvents, were studied in a series of methanol/methyl tertiary butyl ether separation experiments. The flux and selectivity of the membrane samples were affected by the type of solvent used to prepare the casting solution. The sample with DMF consistently gave the highest selectivity and lowest flux, followed by the samples with NMP and acetone. The differences in the performances were attributed to the effects of the volatility and evaporation rates of the solvents. Scanning electron microscopy and atomic force microscopy techniques were used for comparing the morphologies of the membranes. In addition, we used Raman spectroscopy as a novel technique to study the sorption selectivities of the membrane samples prepared with the three different solvents. In a parallel study, the relation between the polymer concentration in the casting solution and the morphology and performance of the membrane samples was studied. Under similar preparation conditions, the morphology of the membrane changed from being porous to being dense when the membrane was prepared with casting solutions with increasing polymer concentration. Also, the selectivity increased and the permeability decreased with increasing polymer concentration in the casting solution. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2882–2895, 2001     

Esterification of glycerol with conjugated linoleic acid and long-chain fatty acids from fish oil

Free fatty acids from fish oil were prepared by saponification of menhaden oil. The resulting mixture of fatty acids contained ca. 15% eicosapentaenoic acid (EPA) and 10% docosahexaenoic acid (DHA), together with other saturated and monounsaturated fatty acids. Four commercial lipases (PS from Pseudomonas cepacia, G from Penicillium camemberti, L2 from Candida antarctica fraction B, and L9 from Mucor miehei) were tested for their ability to catalyze the esterification of glycerol with a mixture of free fatty acids derived from saponified menhaden oil, to which 20% (w/w) conjugated linoleic acid had been added. The mixtures were incubated at 40°C for 48h. The ultimate extent of the esterification reaction (60%) was similar for three of the four lipases studied. Lipase PS produced triacylglycerols at the fastest rate. Lipase G differed from the other three lipases in terms of effecting a much slower reaction rate. In addition, the rate of incorporation of omega-3 fatty acids when mediated by lipase G was slower than the rates of incorporation of other fatty acids present in the reaction mixture. With respect to fatty acid specificities, lipases PS and L9 showed appreciable discrimination against esterification of EPA and DHA, respectively, while lipase L2 exhibited similar activity for all fatty acids present in the reaction mixture. The positional distribution of the various fatty acids between the sn-1,3 and sn-2 positions on the glycerol backbone was also determined.     

PREDICTION OF PINEAPPLE SORPTION ISOTHERMS USING THE ROSS EQUATION

ABSTRACT

A mathematical prediction of pineapple sorption isotherms was developed using Ross, Norrish and Henderson equations. The prediction considered to have the pineapple average composition oflhe main solutes: sucrose, glucose, fructose, citric acid, malic acid, NaCI, KC1 and cellulose as non-solute. Water activity of individual sugars and organic acids was obtained by Norrish's equation and for the two salts by Raoult's Law. Solute solubility at different temperatures was taken into account. Predicted isotherms were compared with the experimental isotherms obtained in laboratory at 30, 35, 40 and 45° C and with the isotherms reported in literature at 30 and 45° C. The generalized correlation coefficients ( r² ) between predicted and experimental isotherms were in the range of 0.8 - 0.98.     

Study of Thermal Degradation Kinetics of Elastomeric Powder (Ground Tire Rubber)

This paper investigates the use of thermogravimetric analysis to study the kinetics of thermal degradation of ground tire rubber (GTR) obtained from reclaimed tires. We analyzed the composition of GTR and determined the content percentage of its components (volatile compounds, rubber, and ash) using thermogravimetric analysis (TGA). T ₁ and T ₂ temperature peaks corresponding to the maximum normalized weight loss rate (NWLR) of the two main rubber components of tires NR (natural rubber) and a BR/SBR (butadiene/styrene-butadiene rubber blend) using the Gaussian deconvolution method has been determined. The influence of GTR particle size and heating rate on reaction rates (dx/dt) and on degradation time during the degradation process has been analyzed.     

Hydrotreatment of Cracked Light Gas Oil

Since worldwide conversion processes are used to upgrade heavy oil to distillates, the hydrotreatment of light gas oil (LGO) as a downstream process has been used more extensively. This fraction (LGO) is produced from thermal or catalytic cracking or hydrocracking processes. It contains high amounts of unsaturates, nitrogen, and sulfur compounds which cause instability while in storage due to gum formation. The use of LGO as a fuel oil for diesel engines plugs the filter and produces sulfur and nitrogen emissions. These sulfur and nitrogen compounds arise from the cracking of heavy cuts and are aromatic-type molecules which are difficult to hydrogenate. This cut also possesses a low cetane index (CI) which must be increased (by aromatic hydrogenation) because of its poor motor performance. Color and color stability are associated with a high bromine number (BN, unsaturated content), nitrogen, and aromatic content. In order to improve these properties, a deep hydrogenation is sometimes required.     

Screening of Soluble Rhodium Nanoparticles as Precursor for Highly Active Hydrogenation Catalysts: The Effect of the Stabilizing Agents

We report the preparation of rhodium nanoparticles (NPs) stabilized by 1-octadecanethiol (ODT), polyvinyl alcohol (PVA), and tetraoctylammonium bromide (TOAB), and their application for hydrogenation catalysis. The three metal–ligand systems correspond to different mechanism of NPs stabilization via strong covalent linkage, chemisorbed atoms and electrostatic interactions, respectively. We found a strong effect of the interaction between the stabilizer and the surface of the metal nanoparticle on the catalytic activity. The Rh NPs were studied as soluble nanoparticle catalysts and as precursors for the synthesis of supported catalysts. All catalysts were tested in the hydrogenation of cyclohexene under similar conditions as a model reaction. Generally, Rh–ODT NPs were inactive, Rh–PVA NPs exhibited distinct activities in solution (aqueous biphasic catalysis) and as a supported catalyst, and Rh–TOAB NPs exhibited similar activities in solution and after immobilization. This last result opens the opportunity for the preparation of highly active Rh NP catalysts both in solution and as a heterogeneous catalyst. Additionally, the stability of the nanoparticles depends on the choice of ligand and on the functionalization of the support surface before immobilization. By optimizing the catalyst synthesis and reaction conditions, turnover frequencies as high as 700,000 h^?1 where observed for stable and recyclable catalyst.