The exchange reactions of divalent metal ion complexes of trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetate (CyDTA) with aquometal ions are sluggish compared to the corresponding reactions of EDTA complexes. Nine metal(II)-CyDTA complexes are studied and in each case the rate of exchange is independent of the concentration of the aquometal ion and depends only upon the acid-dissociation rate of the complex. Second-order rate constants (M~l sec-1, 25°, 0.1 µ) for the reaction of hydrogen ion with metal(II)-CyDTA are 5.6 X 10» (Mg), 7.1 X 105 (Ca), 320 (Mn), 3.2 (Co), 3.5 X 10-4 (Ni), 3.9 (Cu), 170 (Zn), 23 (Pb), and 3.1 (Hg). The rate constants for Co, Ni, Cu, and Zn are consistent with a stepwise-dissociation path in which a proton adds to one of the CyDTA nitrogen atoms before the second metal-nitrogen bond breaks. Thus, the values for the rate constants are in remarkable agreement with values predicted from the characteristic water substitution rate constants of the metal ions and the CyDTA stability constants for hydrogen ion and the metal ions. In contrast Mn, Mg, and Ca depart significantly from this behavior and the rate constants are */io to 4/eoo as large as would be predicted. A mechanism is proposed for these complexes in which two metal-nitrogen bonds are broken in succession as a proton is added to one nitrogen. In this mechanism the water substitution rate constant of the metal ion is no longer applicable because several coordinate bonds are broken in the rate-determining step and the kinetics are not characteristic of a stepwise process.
SynopsisA high pressure differential scanning calorimeter (DSC) and a Fourier transform infrared (FTIR) spectrometer with a prism liquid cell (PLC) were used to monitor the reaction kinetics of styrene-unsaturated polyester resins at elevated curing temperatures and pressures. The thermal method is easy to perform but provides only an overall reaction exotherm. The spectroscopic method can detect the detailed reaction mechanism of copolymerizations. It is, however, less quantitative and the calculation is much more time-consuming compared to the thermal analysis. Reactions of two unsaturated polyester resins with different molecular structure were measured by these two methods. Results showed that applying cure pressure on unsaturated polyester resins reduced the reaction rate but increased the final conversion. The styrene reaction was enhanced more than the polyester reaction at high curing temperatures.
Two structures are possible for the product of quaternization of an N‐alkylimidazoline, i.e., symmetrical and unsymmetrical. The literature employs both versions, with no unambiguous proof available for either. Proton and13C nuclear magnetic resonance spectroscopy have been used in this work. The product of quaternization under neutral conditions is shown to be symmetrical. This can be easily rationalized on the basis of resonance stabilization caused by delocalization of the positive charge.
Specialty monomers containing t h e aminimide functional group were used to prepare modified thermosetting acrylic solution, emulsion, and powder coatings. Since t h e aminimide residue is a heat-activated isocyanate precursor, acrylic polymers with urethane cross-links are possible. Coatings of excellent film performance and outdoor durability were obtained from a number of formulations and are described.Attenuated total reflectance infrared spectroscopy was used to determine rate of cure. T h e reaction kinetics or cross-linking rates were shown to b e a function of baking time/temperature relationship.Presently available acrylic resins provide quality surface coatings. As binders, they are used because of their color, color retention, flexibility, non-yellowing properties, resistance to outdoor weathering, and film durability. Such wide-ranging applications as lacquers, thermoplastic airdry emulsion paints, thermosetting emulsion or solution industrial bake finishes, and water-dispersible or watersoluble resins for industrial metal bake primers show the wide utility of these resin systems. Additional versatility is being demonstrated by the fact that thermosetting acrylic resins are also designed for powder coatings.In this paper, we will discuss the thermosetting type which requires baking. We will describe recently available specialty monomers based on the aminimide functional group (-COS~-N-RS) and their utility in solution, emulsion, and powder coatings of the acrylic type. This investigation was aimed a t producing one-package coatings for general industrial purposes, utilizing the isocyanate-hydroxyl reaction to give acrylic copolymers cross-linked uia
A very promising new entry into the family of polymers for advanced composites, for aerospace and heavy duty industrial applications requiring high service temperature and/or low flammability, are bisoxazoline-phenolic resins derived from the step-growth copolymerization of 1,3 (or 1,4)-phenylene bisoxazoline (PBOX) and phenol-free phenolic resins. This new resin system offers a very attractive group of properties, including high modulus, high compressive and shear strengths, excellent toughness, high heat distortion temperature, no volatiles evolution and low shrinkage (<1%) during cure, low flammability and low smoke production, good electrical properties, relatively low coefficient of thermal expansion, very good thermal shock resistance and machinability, and excellent adhesion to carbon fibers, fiberglass and powdered (5 to 20 μm) metal fillers (e.g., iron and aluminum).In this paper are presented example scanning electron microscopy (SEM) micrographs of PBOX-phenolic interfacial regions with both reinforcing fibers and metallic fillers. Carbon fiber reinforced composite specimens were examined by SEM (CamScan Series 4 instrument) after testing to failure using standard ASTM shear, flex and compression tests.
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