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Solid bisphenol-A epoxy
resin of medium molecular mass was cured using a Lewis acid initiator (ytterbium(III)
trifluoromethanesulfonate) in three different proportions (0.5, 1 and 2 phr).
A kinetic study was performed in a differential scanning calorimeter. The
complete kinetic triplet was determined (activation energy, pre-exponential
factor, and integral function of the degree of conversion) for each system.
A kinetic analysis was performed with an integral isoconversional procedure
(free model), and the kinetic model was determined both with the Coats-Redfern
method (the obtained isoconversional value being accepted as the effective
activation energy) and through the compensation effect. All the systems followed
the same isothermal curing model simulated from non-isothermal ones. The growth-of-nuclei
Avrami kinetic model A3/2 has been proposed as the
polymerization kinetic model. The addition of initiator accelerated the reaction
especially when 2 phr was added. 0.5 and 1 phr showed very few kinetic differences
between them. 相似文献
23.
Jason S. Overby Nathan J. Schoell Timothy P. Hanusa 《Journal of organometallic chemistry》1998,560(1-2)
Two equivalents of K[Cp′] (Cp′=C5(i-Pr)3H2, C5(i-Pr)4H, C5(t-Bu)2H3) react with CrCl2 in THF to give the corresponding chromocenes, Cp′2Cr, in good yield. Despite the presence of bulky substituents on the rings that could affect their properties, the complexes are extremely air- and moisture-sensitive, and possess a low-spin ground state. The low-spin paramagnetic nature of each chromocene was confirmed by magnetic susceptibility measurements. The solid-state structure of [C5(i-Pr)3H2]2Cr was obtained using single crystal X-ray analysis. It displays rigorously parallel rings, with an average Cr–C(ring) distance of 2.17(1)Å; the chromium resides on a crystallographically imposed inversion center. The orientation of the isopropyl groups minimizes unfavorable steric interactions between the rings. 相似文献