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A novel hyperbranched polysiloxane containing epoxy and phosphaphenanthrene groups (EP-HPSi) was synthesized through a ring-open reaction between P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and epoxy group of a hyperbranched polysiloxane. EP-HPSi was used to modify cyanate ester (CE) resin. The influences of the content of EP-HPSi in modified CE resin system as well as the molar ratio between DOPO and epoxy group on the structure and integrated performance of the EP-HPSi/CE system were systematically studied. Results show that EP-HPSi is a multi-functional flame retardant, which endows CE resin with not only outstanding flame retardancy, but also significantly increased toughness and stiffness. For example, EP-HPSi/CE system has a 40–80oC lower curing temperature than CE; moreover, the impact and flexural strengths of EP-HPSi/CE system are about 1.6–2.2 and 1.3 times higher than that of CE resin, respectively. These attractive integrated performances of EP-HPSi/CE system are attributed to the special structure of EP-HPSi, and its influence on the cross-linked network. This investigation suggests that the method proposed herein is a new approach to develop high performance flame retardant resins for cutting-edge industries, especially those that simultaneously have outstanding thermal resistance, toughness, and stiffness. [Supplementary materials are available for this article. Go to the Publisher's online edition of Soft Materials for the following free supplemental resource: Figure S1] [ABSTRACT FROM AUTHOR]

A new hyperbranched polysiloxane containing maleimide (HPMA) was synthesized through the reaction between N-(4-hydroxyphenyl) maleimide and 3-glycidoxypropyltrimethoxysilane, which was then used to prepare cyanate ester (CE) resin-based hybrids (coded as HPMA x/CE, where x is the weight fraction of HPMA in the hybrid). The curing behavior of uncured hybrids and the typical properties (impact strength and dielectric properties) of cured hybrids were systemically investigated. Results show that the performance of hybrids is greatly related with the content of HPMA. Hybrids have obviously lower curing temperature than CE, overcoming the poor curing characteristics (higher curing temperature and longer curing time) of neat CE, for example, the curing peak temperature of HPMA20/CE is about 65°C lower than that of CE. In the case of cured resin and hybrids, the hybrids exhibit decreased dielectric constant and loss than CE resin; moreover, the former also exhibits lower water absorption than the latter. Specifically, the dielectric loss of HPMA15/CE hybrid is only about 27% of that of neat CE resin. In addition, the hybrids with suitable contents of HPMA have significantly improved impact strengths. The overall improved properties suggest that HPMA x/CE hybrids have great potential in applications needing harsh requirements of curing feature, dielectric properties, and toughness. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Novel modified cyanate ester (CE) resins with decreased dielectric loss, improved thermal stability, and flame retardancy were developed by copolymerizing CE with hyperbranched phenyl polysiloxane (HBPPSi). HBPPSi was synthesized through the hydrolysis of phenyltrimethoxysilane, and its structure was characterized by 1H-NMR, 29Si-NMR, and Fourier transform infrared spectra. The effect of the incorporation of HBPPSi into CE resin on the curing behavior, chemical structure of cured networks, and typical performance of HBPPSi/CE resins were systemically evaluated. It is found that the incorporation of HBPPSi into CE network obviously not only catalyzes the curing of CE, but also changes the chemical structure of resultant networks, and thus results in significantly decreased dielectric loss, improved thermal stability, and flame retardancy as well as water absorption resistance. For example, in the case of the modified CE resin with 10 wt% HBPPSi, its limited oxygen index is about 36.0, about 1.3 times of that of neat CE resin, its char yield at 800°C increases from 31.6 to 35.4 wt%; in addition, its dielectric loss is only about 61% of that of neat CE resin at 1 kHz. All these changes of properties are discussed from the view of the structure-property relationship. The significantly improved integrated properties of CE resin provide a great potential to be used as structural and functional materials for many cutting-edges fields. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]