The influence of chromate quenching and chloride contamination level on the performance of the painted hot-dipped galvanized steel (duplex system)

The influences of the chromate quenching step and the surface chloride contamination levels of galvanized steel on the performance of duplex systems were studied. Steel panels were galvanized in a commercial steel bath adopting three different postdipping procedures. A comparative study of the galvanized steel, both painted and nonpainted, was performed by electrochemical techniques. It was verified that the chloride contamination level of the galvanized steel surfaces is the main cause of duplex system failures. An explanation for the influence of the chromate quenching on the performance of duplex systems was presented.     

Phase and Rheological Behavior of Cetyldimethylbenzylammonium Salicylate (CDBAS) and Water

The temperature–composition phase diagram in the diluted region of the cationic surfactant cetyldimethylbenzylammonium salicylate/water system was studied with a battery of techniques. The Krafft temperature (T _k = 33 ± 1 °C) was measured by differential scanning calorimetry, polarizing microscopy, conductimetry, viscosimetry, and rheometry. The critical vesicle concentration (cvc, ~0.002 wt%) and a vesicle–micellar transition (cvm, ~0.005 wt%) was detected at a temperature of 35 °C. Below T _k and concentrations ≤2 wt%, a transparent solution is formed (I). Above 2–8.5 wt%, a lamellar (L₁) phase forms. At higher concentrations and up to 12 wt%, a second lamellar phase (L₂) is detected. From 12.4 to 15.5 wt%, an emulsion phase (E) is formed. Rheological dynamic measurements for the I phase indicate that the system exhibits a predominantly viscous behavior (G′ < G″) for concentrations lower than the overlap or entanglement concentration (C _e, ~0.75 wt%). At higher concentrations, wormlike micelles form and the elastic behavior predominates (G′ > G″). The elastic (G′) modulus collapses in a concentration–time master curve in the whole reduced frequencies range ωτ _c examined, whereas the viscous modulus (G″) collapses only at reduced frequencies lower than 0.1. Reduced stress plotted as a function of the reduced shear rate yields a good superposition of the curves at the different concentrations up to the onset of the non-linear behavior.     

Asymmetric Aza‐Morita–Baylis–Hillman‐Type Reactions: The Highly Enantioselective Reaction between Unmodified α,β‐ Unsaturated Aldehydes and N‐Acylimines by Organo‐co‐catalysis

The highly enantioselective organo‐co‐catalytic aza‐Morita–Baylis–Hillman (MBH)‐type reaction between N‐carbamate‐protected imines and α,β‐unsaturated aldehydes has been developed. The organic co‐catalytic system of proline and 1,4‐diazabicyclo[2.2.2]octane (DABCO) enables the asymmetric synthesis of the corresponding N‐Boc‐ and N‐Cbz‐protected β‐amino‐α‐alkylidene‐aldehydes in good to high yields and up to 99% ee. In the case of aza‐MBH‐type addition of enals to phenylprop‐2‐ene‐1‐imines, the co‐catalytic reaction exhibits excellent 1,2‐selectivity. The organo‐co‐catalytic aza‐MBH‐type reaction can also be performed by the direct highly enantioselective addition of α,β‐unsaturated aldehydes to bench‐stable N‐carbamate‐protected α‐amidosulfones to give the corresponding β‐amino‐α‐alkylidene‐aldehydes with up to 99% ee. The organo‐co‐catalytic aza‐MBH‐type reaction is also an expeditious entry to nearly enantiomerically pure β‐amino‐α‐alkylidene‐amino acids and β‐amino‐α‐alkylidene‐lactams (99% ee). The mechanism and stereochemistry of the chiral amine and DABCO co‐catalyzed aza‐MBH‐type reaction are also discussed.     

Formulation and characterization of leather and rubber wastes composites

Residues from footwear roughing and carding operations represent 5–15% (w/w) of the solid wastes generated by shoe‐making companies. These wastes are mainly composed by chromium tanned leather and sole materials, and are mostly land filled. Sometimes leaching tests show these wastes as hazardous due to chromium in the leachate. This work aims at a more sustainable option for these wastes by recycling them in styrene butadiene rubber (SBR) and acrylonitrile butadiene rubber (NBR). Thus, they were charged with: (i) ≤1 mm leather waste fibers in the range of 10–25 parts per hundred parts of rubber (phr); and (ii) leather and soles industrial carding and roughing wastes in the range of 20–100 phr. The leather waste fibers‐rubber composites tear strength is increased till 25 phr and both tension and elongation at break decrease within the acceptable range till 12.5 phr for SBR and 15 phr for NBR. In the case of leather and sole carding and roughing wastes, composites tear strength increases till 100 phr, and tension and elongation decrease within the acceptable range till 20 phr. The composite materials at the end of their life cycle may be considered inert or non‐hazardous wastes. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Solventborne paint systems on carbon steel and hot-dip galvanized steel for a wide range of atmospheric exposures

The paper analyzes the performance of solventborne paint systems applied on carbon steel and hot-dip galvanized steel in a wide range of atmospheric exposures. The study has involved paint systems exposure for 3.5 years in eight natural atmospheres. The atmospheric conditions cover from temperate rural climates to tropical severe marine and Antarctic coastal regions. The paint systems included several alkyds formulated with a variety of pigments (anticorrosive and barrier), epoxies, chlorinated rubber, and zinc-rich (ethyl silicate and epoxy). It has been concluded that in rural and urban atmospheres alkyd systems afford equivalent anticorrosive protection of steel to the epoxy/polyurethane system. The toxic red lead pigment may be replaced in long linseed-oil alkyd primer paints by non-toxic pigments, such as a mixture of micaceous iron oxides (MIO) and black iron oxides or zinc phosphate, without affecting the anticorrosive properties of the paint system. In aggressive atmospheres (industrial, marine), paint systems including zinc-rich primers or applied on galvanized steel must be used, especially in surface regions with coating faults (scribes).     

Synthesis and characterization of poly (styrene‐b‐[(butadiene)1−x‐(ethylene‐co‐butylene)x] ‐b‐styrene) star‐like molecular polymers produced by partial hydrogenation of SBS

This article reports the synthesis and characterization of four arm star‐shaped poly(styrene‐b‐[(butadiene)_1?x‐(ethylene‐co‐butylene)_x]‐b‐styrene) (SBEBS) copolymers. A series of SBEBS copolymers with different compositions of the elastomeric block were produced by hydrogenating a given poly(styrene‐b‐butadiene‐b‐styrene) (SBS) copolymer using a catalyst prepared from bis(η⁵‐cyclopentadienyl)titanium(IV) dichloride and n‐butyllithium. The characterization was accomplished by proton nuclear magnetic resonance spectroscopy (¹H NMR), infrared spectroscopy (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The results indicate that there is a selective saturation of the polybutadiene block over the polystyrene block; this selectivity was determined by the Ti/Li molar ratio and the concentration of Ti. It was observed that the saturation rate of the 1,2‐vinyl was higher than that of the 1,4‐trans and 1,4‐cis poly(butadiene)‐b isomers. The DSC and DMA results indicate that the degree of hydrogenation had a profound effect on the polymer's relaxation behavior. All samples exhibited a biphasic system behavior with two distinct transitions corresponding to the elastomeric and polystyrene blocks. SBEBS copolymers with higher saturation levels (>33%) exhibited a crystalline character. The TGA results indicated a characteristic weight loss temperature in all samples, with slightly higher thermal degradation stabilities in the materials with higher degrees of saturation. POLYM. ENG. SCI., 54:2332–2344, 2014. © 2013 Society of Plastics Engineers     

Isolation and Structural Elucidation of Antiproliferative Compounds of Lipidic Fractions from White Shrimp Muscle (Litopenaeus vannamei)

Shrimp is one of the most popular seafood items worldwide, and has been reported as a source of chemopreventive compounds. In this study, shrimp lipids were separated by solvent partition and further fractionated by semi-preparative RP-HPLC and finally by open column chromatography in order to obtain isolated antiproliferative compounds. Antiproliferative activity was assessed by inhibition of M12.C3.F6 murine cell growth using the MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) assay. The methanolic fraction showed the highest antiproliferative activity; this fraction was separated into 15 different sub-fractions (M1–M15). Fractions M8, M9, M10, M12, and M13 were antiproliferative at 100 µg/mL and they were further tested at lower concentrations. Fractions M12 and M13 exerted the highest growth inhibition with an IC₅₀ of 19.5 ± 8.6 and 34.9 ± 7.3 µg/mL, respectively. Fraction M12 was further fractionated in three sub-fractions M12a, M12b, and M12c. Fraction M12a was identified as di-ethyl-hexyl-phthalate, fraction M12b as a triglyceride substituted by at least two fatty acids (predominantly oleic acid accompanied with eicosapentaenoic acid) and fraction M12c as another triglyceride substituted with eicosapentaenoic acid and saturated fatty acids. Bioactive triglyceride contained in M12c exerted the highest antiproliferative activity with an IC₅₀ of 11.33 ± 5.6 µg/mL. Biological activity in shrimp had been previously attributed to astaxanthin; this study demonstrated that polyunsaturated fatty acids are the main compounds responsible for antiproliferative activity.