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The cross-linking mechanisms of sulfur vulcanization are not analytically known and, therefore, reticulation kinetics has to be deduced macroscopically from standardized tests. One of the most popular laboratory test to characterize curing and reversion is the oscillating disk rheometer ODR, which gives a quantitative assessment of scorch, cure rate, and state of cure. In this article, a numerical two-step approach, which is based on the utilization of experimental ODR data and aimed at predicting the degree of vulcanization of thick rubber items cured with accelerated sulfur, is presented. In step one, a composite numerical three-function curve is used to fit experimental rheometer data, able to describe the increases of the viscosity at successive curing times and at different controlled temperatures, requiring only few points of the experimental cure curve to predict the global behavior. Both the case of indefinite increase of the torque and reversion can be reproduced with the model. In step two, considering the same rubber compound of step one, numerical cure curves at different temperatures are collected in a database and successively implemented in a Finite Element software, which is specifically developed to perform thermal analyzes on complex 2D/3D geometries. As an example, an extruded thick EPDM section is considered and meshed through eight-noded isoparametric plane elements. Several FEM simulations are repeated by changing exposition time tc and external curing temperature Tn, to evaluate for each (tc,Tn) couple the corresponding mechanical properties of the item at the end of the thermal treatment. A recently presented bisectional approach, alternating tangent (AT), is used to drastically reduce the computational efforts required to converge to the optimal solution associated with the maximum value of an output property, tensile strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

A variety of diphenyldiphosphinites have been prepared in a very stable form as PtII or PdII complexes by adding diols to a solution containing cis-[MCl2(PPh2Cl)2] (M = Pt or Pd) preformed in situ from cis-[MCl2(1,5-COD)] (M = Pt; M = Pd) and PPh2Cl. This synthetic pathway can be used for diphosphinites derived from aliphatic 1,2 and 1,3 diols and also from the aromatic catechol. Besides the P−O bond, it is also shown here that the P−N bond can also be formed via nucleophilic attack of an amine group on coordinated PPh2Cl in the presence of a base resulting in some AMPP and BAMP complexes of PtII and PdII. The X-ray crystal structures of the [cis-1,2-cyclohexanediyl bis(diphenylphosphinite)]platinum dichloride, of the AMPP palladium complex from (1R,2S)-(−)-norephedrine and of the BAMP palladium complex [P,P′-diphenyl-1,2-cyclohexanediylbis(imino)bisphosphane]palladium dichloride have been determined. The chemical and optical stabilities of many complexes in solution have been monitored by 31P NMR spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

A detailed microstructural characterization of ethylene-propene copolymers, obtained with a high yield Ti-catalyst and showing elastomeric properties, was carried out by 13C NMR spectroscopy. These copolymers show no inversions in propene insertion, a tendency to form blocks of ethylene and propylene, and the presence of both isotactic and atactic blocks of propylene. Furthermore, in these polymers the reactivity ratio product (r1 · r2) and the experimental versus calculated triad distribution point to the presence of components which are heterogeneous with respect to the monomer distribution and composition. 13C NMR analysis of fractions, separated by hexane and ether, supports the above hypothesis.