Chemical modification of dicyclopentadiene-based epoxy resins to improve compatibility and thermal properties

Application of Mathematical and Experimental Approach in Description of Sedimentation of Powder Fillers in Epoxy Resin

In this paper, sedimentation inhibition attempts were examined using colloidal silica in a mathematical and experimental approach. Experimental results were validated by a two-step verification process. It was demonstrated that application of quantitative metallography and hardness measurements in three different regions of samples allows us to describe the sedimentation process using modified Stokes law. Moreover, proper application of Stokes law allows one to determine the optimal colloidal silica amount, considering characteristics of applied filler (alumina or graphite). The results of mathematical calculations have been confirmed experimentally—the experimental results show good agreement with the calculated data.

Synthesis of a Flame Retardant for Epoxy Resins: Thermal Stability, Flame Retardancy, and Flame-Retardant Modes

A polyphosphonate (PDPA) flame retardant that contains phenyl phosphonic dichloride and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide groups, has been synthesized. The flame retardant was introduced into epoxy resins (EP) and cured by 4,4’-diamino diphenylmethane. The vertical burning, limited-oxygen index and cone calorimeter tests reveal that the PDPA can enhance the flame-retardant properties of the EP significantly. With only a 4 wt% PDPA loading, the EP composites achieved a limited-oxygen index value of 33.4% and a V-0 rating in the vertical burning test, and the peak heat release rate and total heat release were decreased by 40.9% and 24.6%, respectively. The thermal properties and gas pyrolysis products of the EP composites were evaluated by thermogravimetric analysis and thermogravimetric analysis-Fourier transform infrared spectroscopy, and the morphology and structure of residual char were characterized by scanning electron microscopy, Flourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. To explain the combined effects of the condensed and gas phases, modes of the flame-retardant action are proposed.

Versatile Manganese Catalysis for the Synthesis of Poly(silylether)s from Diols and Dicarbonyls with Hydrosilanes

Poly(silylether)s are interesting materials because of their degradation property under hydrolytic conditions and have been prepared via hydrosilylation polymerization from dicarbonyl and hydrosilanes, and via dehydrogenative cross-coupling of diols and hydrosilanes under catalytic conditions. Here, we present a manganese-salen compound based on an inexpensive and nontoxic metal that could effectively catalyze both polymerization reactions with hydrosilane. A series of poly(silylether)s containing various aliphatic and aromatic backbones have been synthesized from diol and dicarbonyl substrates. Moderate to high yields of polymers with number-average molecular weights up to 15 kg/mol are obtained. Because of the dual activity of the manganese catalyst, unsymmetrical substrates with mixed functional groups, such as p-hydroxybenzaldehyde, p-hydroxy benzylalcohol, and 3-(4-hydroxyphenyl)-1-propanol, have been employed to afford poly(silylether)s with multiple silicon connectivity in the main chain.

High-performance transparent solvent-free silicone resins with stable storage and low viscosity based on new hyperbranched polysiloxanes

Five new hyperbranched polysiloxanes, for example, methylhydrogen siloxanes (MHSis), with varying concentrations of silicon–methyl (Si-Me) groups were synthesized and characterized, and then a series of MHSi/poly(methylphenylvinylsilicone) (PSi) resins were prepared to investigate the influence of the structures and concentrations of MHSi on the integrated properties of both uncured and cured MHSi/PSi resins. The results show that the compatibility between MHSi and PSi is closely related to the concentration of Si-Me groups in the MHSi as well as the molar ratio of MHSi and PSi. If MHSi has a suitable concentration of Si-Me groups, and the molar ratios of MHSi to PSi are appropriate, transparent MHSi/PSi resins with stable compatibility can be obtained. In addition, these compatible resins show good thermal stability with dynamic mechanical and dielectric properties. They exhibit a great potential for use as high-performance solvent-free silicone resins in either vacuum pressure impregnating process or liquid-molding techniques.