CE-Epoxy Reaction Mechanism

Using monofunctional model compounds, Fyfe et al. recently studied the reaction by high resolution 1H-, 13C-, and 15N-NMR spectroscopy and mass spectroscopy [178]. The major cross reaction product is a racemic mixture of enantiomers containing an oxazolidinone ring formed from one cyanate and two epoxy molecules. Epoxy consumption lags behind the cyanate consumption as triazine formation is faster than both the self-polymerization of epoxy and cy- 

A very recent study based on FTIR analysis of the isothermal co-reaction between tetrafunctional epoxy and cyanate ester resins at different stoichiometric ratios and temperatures substantiates some of these findings. Rheological char- 

As mentioned earlier, the cyanate-epoxy systems find many commercial applications. Many multifunctional formulations, principally based on CE/epoxy, have been claimed. Generally, the properties of epoxies are improved on co-cur-ing by cyanate ester and the blend is more cost-effective than cyanate alone. The applications of these blends, as covered by patents, has been referred to in a review by Penczek and Kaminska [184]. Most of their applications are in copper clad laminates [185-191], fire resistant formulations [192], aircraft structures [193], and in semiconductor devices [194-196]. Due to the commercial significance of the blends, the information on the epoxy-cyanate systems is still covered by patents and some of the most relevant and recent ones have been referred to in this review. 

Mol fraction of epoxy groups in the blend Tensile strength (MPa) for neat resin (0°) Compressive strength (MPa) for composite Flexural (MPa) Compo- site strength Neat resin ILSS (MPa Ambient Tempera- ture ) Retention of ILSS at 150 °C (%) 

Mol fraction of epoxy groups in the blend Moisture Absorption (%) Dielectric constant (1 MHz, 60% RH) Dissipation factor (tan 8) CTE (10 5 °C-1) 

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