Suppression of metallocene catalyst leaching by the removal of free trimethylaluminum from methylaluminoxane

The leaching of the catalyst zirconocene dichloride (Cp₂ZrCl₂) from an SBA‐15 silica support during ethylene polymerization was studied; severe leaching was observed when commercial methylaluminoxane (MAO) was used as the cocatalyst. However, the removal of free trimethylaluminum (TMA) from an MAO solution with a sterically hindered phenol reduced the catalyst leaching by 97–100%. The results obtained from the leaching experiments with TMA‐free MAO suggested that the major reason for catalyst leaching was the free TMA in the commercial MAO solution, not the pure MAO itself. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4632–4635, 2006     

Determination of transforming growth factor-beta 1 (TGF-beta 1) and insulin-like growth factor (IGF-1) in bovine colostrum samples

The major growth factors in bovine colostrum are transforming growth factor-beta s (TGF-beta 1 and TGF-beta 2) and insulin-like growth factors (IGF-1 and IGF-2). Recently, TGF-beta 2 content of bovine colostrum was measured using a TGF-beta 2 specific ELISA (1) and now we have validated ELISAs for for bovine TGF-beta 1 and IGF-1. The concentrations of IGF-1 and TGF-beta 1 in the first milking after calving were 248-1850 ng/ml and 12.4-42.6 ng/ml, respectively, and they declined in correlation with total protein concentration to 27.0-101 ng/ml (IGF-1) and 0.80-3.49 ng/ml(TGF-beta 1) by the fifth milkings. The amount of TGF-beta 1 was on average 5.3 +/- 1.4% of that of TGF-beta 2 and there is a high correlation (r = 0.966) between the concentrations of these growth factors in the same samples. No free TGF-beta 1 form of could be detected.     

Friction and a Tribochemical Reaction between Ice and Hexagonal Boron Nitride: A Theoretical Study

Friction between ice-Ih and hexagonal boron nitride (h-BN) has been determined by periodic ab initio calculations. Surfaces of ice-Ih and h-BN were brought into sliding contact, and the interaction energies were calculated as a function of interplanar distance and lateral displacement of the surfaces. The friction between the surfaces was calculated from the interaction energies, producing a friction coefficient of 0.140. Friction is further influenced at high loads by a tribochemical reaction between ice-Ih and h-BN.     

Effects of silane and the lowering of pH on the properties of phenol–formaldehyde resol resins and resin coatings

Phenol–formaldehyde resol resins were modified by the addition of silane (3‐aminopropyltriethoxysilane) and the lowering of pH (formic acid). The effects of the modifications on the properties of the resins during storage were studied through comparison with the parent resins and by viscosity measurements, NMR spectroscopy, ultraviolet–visible spectroscopy, and differential scanning calorimetry. Resin coatings on paper were prepared to determine the influence of discoloration of the resin solution on the color of the cured resin. A decrease in the pH of the NaOH‐catalyzed resin solutions lightened the color of the solutions and corresponding coatings, whereas silane additions made the coatings slightly more yellow. The lowering of pH increased the viscosities and decreased the reactivities of the resin solutions compared with the unmodified reference resins during storage. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1933–1941, 2007     

Viscose fiber/polyamide 12 composites: Novel gas‐phase method for the modification of cellulose fibers with an aminosilane coupling agent

The objective of this study was to improve the adhesion between viscose fibers and polyamide 12 and, thereby, the mechanical properties of the corresponding composites. The cellulose fiber surface was chemically modified in the vapor phase with a silyl coupling agent, aminosilane [(3‐aminopropyl) triethoxysilane]. This new gas‐phase treatment for cellulose fibers proved to be highly effective. Relative to composites without the coupling‐agent treatment, the tensile strength of the composites (40/60 wt % fiber/polymer) increased from 49.3 to 87.4 MPa; the improved adhesion between the fibers and matrix induced by the coupling agent was observed under a scanning electron microscope. The presence and bonding of the coupling agent on the fibers after the reaction was confirmed by solid‐state ²⁹Si‐NMR. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4478–4483, 2006     

Origin of bicyclic fatty acids in tall oil

It was shown that two bicyclic fatty acids present in Finnish tall oil were formed from (5Z, 9Z, 12Z)-5, 9, 12-octadecatrienoic acid, pinolenic acid (I). Under the alkaline conditions of sulfate pulping, pinolenic acid forms conjugated isomers which undergo Diels-Alder cyclization during the heating in the tall oil distillation. The cyclization products, here called cyclopinolenic acids, are bicyclic fatty acids and stereoisomers of 4-(5-pentyl-3a, 4,5,7a-tetrahydro-4-indanyl) butanoic acid (IV and V).     

Laser-induced heterometallic phase deposition from solutions of supramolecular complexes

Heterometallic (Au–Cu) phase precipitation on the surface of soda-lime glass as a result of laser-induced chemical liquid phase deposition (LCLD) is demonstrated for the first time. The precipitation of heterometallic structures was carried out under Ar⁺ laser irradiation from the solutions of supramolecular complexes. Energy dispersive X-ray (EDX) analysis showed that the deposits consist of both Au and Cu. Morphology of the deposited structures was found to be dependent on the used solvents: delocalized sparse surface structures in the case of the dichloromethane solution, close packed nanoparticles for the dimethyl formamide and homogeneous phase with nano-pores for the acetone solution. In accordance to the SEM photos and scan EDX analysis the homogeneous heterometallic phase with fixed Au/Cu ratio was achieved for the acetone solution of supramolecular complex. The observed formation of the heterometallic phase was explained by the laser-initiated intramolecular reduction process of the supramolecular metal core.     

Soiling of plasticized poly(vinyl chloride)

The effects of three plasticizers and two plasticizer concentrations on the topography and soiling of poly (vinyl chloride) (PVC) were studied. Palmitic acid and triolein were chosen to represent solid and liquid soils. The feasibility of using infrared spectroscopy to quantify the amount of soil on PVC was examined. The structure of the solid model soil on plasticized PVC was studied with optical microscopy and atomic force microscopy. Palmitic acid formed two different structures on the PVC surface. Both the type and concentration of the plasticizer influenced the structure of the oily soil on plasticized PVC. The wetting of plasticized PVC with the liquid oily soil was compared to wetting with water through the measurement of the contact angles. Plasticized PVC was hydrophobic and oleophilic. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Friction Paths for Cubic Boron Nitride: An Ab Initio Study

Friction coefficients for cubic boron nitride were determined with the use of hybrid density functional B3LYP calculations. Two cluster models and an infinite periodic model were applied. Various contacts between duplicated surfaces and different sliding paths of the surfaces with respect to each other were taken into consideration, and friction coefficients were derived. The calculations suggest that three different sliding paths contribute to the friction, the friction coefficient for the periodic model being 0.21 at its lowest. This value is in agreement with previous experimental studies, where a friction coefficient of 0.1–0.2 has been measured for cubic boron nitride.