Dicyanate ester of bisphenol A

Densely cross-linked PCN networks, synthesized by polymerization, via cy-clotrimerization reaction, of dicyanic ester of bisphenol A [159-161], consist of rigid triazine heterocycles as junctions connected with bisphenol A remainders (see a scheme in Fig. 26). At the total conversion of cyanate groups (Xcn pcn 1). PCN exhibits high Tg 300°C and rigidity, good adhesion to different substrates and chemical resistance, as well as low values of dielectric constant and water uptake. This allowed in particular its application as the matrix for glass- and aramid fiber-reinforced plastics in the electronics and aerospace industries. 

Fainleib A., Saiter J.M., Youssef B., Garda M.R., Danilenko I., Grenet J. Novel in situ sequential IPNs from oligourethanemethacrylate and dicyanate ester of bisphenol A synthesized by combined photo/thermo curing. Scientific Israel-Technological Advantages, 10(1), 15-25 (2008). 

Of these, apart from the amino-formaldehyde systems used on wooden structures, the aerospace industry currently concentrates on epoxies, phenolics and polyimides for the majority of its structural bonding applications it is the epoxies that are the real workhorse for the industry. Acrylic and polyurethane chemistries are used, but in very few applications of a structural nature. The relatively novel chemistry based on cyanate esters, for example Arocy B 10 (dicyanate ester of Bisphenol A) ... 

Polyurethane/polycyanurate grafted semi-IPNs were prepared by polycyclotrimerization of dicyanate ester of bisphenol A (DCEBA) in the immediate presence of TPU, as described in Section 3.1. During semi-IPN synthesis, at... 

Difunctional cyanate ester monomers were discovered 30 years ago by Ernst Grigat, an organic chemist now retired from Bayer of Levetkusen, Germany, who was also the first to succeed in making organic cyanate esters at all. Bayer licensed dicyanate/polycyanurate technology to Mitsubishi Gas Chemical Co., Tokyo, and to the then Celanese Corp., New York City. Mitsubishi improved the resin by copolymerization of bisphenol A dicyanate with the bis-(maleimide) of 4,4 -methylenedianiline. 

The predominant curing pathway for cyanate ester is via cyclotrimerization using metal coordination catalysts. Three types of metal coordination catalysts are used metal naphthenates, metal acetylacetonates (AcAc), and metal octoates. Of these, Cu AcAc and Mn octoate are the most popular. Nonylphenol is also required as a cocatalyst. Reaction 5 shows the cyclotrimerization reaction of bisphenol A dicyanate to form the triazine network structure ... 

Aryl cyanate esters such as bisphenol A dicyanate can be processed much like epoxy resins for many applications. This may be implied by comparing the monomer structure of bisphenol A diglycidyl ether to bisphenol A dicyanate. 

Similarities to epoxy resin include no volatile polymerization byproducts stable B-stage resins possible low shrinkage, high adhesion and void free structures. High purity makes cyanate esters very attractive for use in electronic applications. The performance of bisphenol A dicyanate resins in printed wiring board laminates was described by Weirauch et al(4). Mobay Chemical (and Bayer) introduced products of this type for PWB applications in the United States in 1976-78. These "Triazine A resins were not commercially successful and were withdrawn from the market about 1979. 

Fainleib A, Grigoryeva 0, Hourston D. Synthesis of inhomogeneous modified polycyanurates by reactive blending of bisphenol A dicyanate ester and polyoxypropylene glycol. Macromol. Symp., 164, 429-442 (2001). 

The fluorine content, density, critical surface energy, glass transitions, thermal expansion coefficient above and below the glass transition, and 300°C isothermal thermogravimetric stabilities of the fluoromethylene cyanate ester resin system with n = 3, 4, 6, 8, 10 are summarized Table 2.2. Also included for the purpose of comparison are the corresponding data for the aromatic cyanate ester resin based on the dicyanate of 6F bisphenol A (AroCy F, Ciba Geigy). 

A variety of CEs with tailorable physico-chemical and thermo-mechanical properties have been synthesized by appropriate selection of the precursor phenol [39,40]. The physical characteristics like melting point and processing window, dielectric characteristics, environmental stability, and thermo-mechanical characteristics largely depend on the backbone structure. Several cyanate ester systems bearing elements such as P, S, F, Br, etc. have been reported [39-41,45-47]. Mainly three approaches can be seen. While dicyanate esters are based on simple diphenols, cyanate telechelics are derived from phenol telechelic polymers whose basic properties are dictated by the backbone structure. The terminal cyanate groups serve as crosslinking sites. The polycyanate esters are obtained by cyanation of polyhydric polymers which, in turn, are synthesized by suitable synthesis protocols. Thus, in addition to the bisphenol-based CEs, other types like cyanate esters of novolacs [37,48], polystyrene [49], resorcinol [36], tert-butyl, and cyano substituted phenols [50], poly cyanate esters with hydrophobic cycloaliphatic backbone [51], and allyl-functionalized cyanate esters [52] have been reported. 

Rubbers and PESs are initially miscible with cyanate ester monomers. Phase separation occurs during the reaction. By plotting the phase diagrams (temperature vs. conversion), it is possible to compare the effects of chain ends and AN content in butadiene-acrylonitrile random copolymers and the effect of molar mass in PES. The cyanate ester monomer based on bisphenol A is a better solvent than DPEDC, and both dicyanates are better solvents than DGEBA. 

Some examples of what may be considered as actual thermosetithermoset blends are the epoxy and bismaleimide thermosets modified with aromatic dicyanate esters such as bisphenol A dicyanate. Aromatic cyanates crosslink by cyclotrimerization to form a network of triazine ethers. 

Similar hybrid thermosets consisting of bismaleimide resins mixed with bisphenol A dicyanate ester have been commercially available (BT resin, Mitsubishi gas chemical). The presence of cross-linked triazine ether network in the matrix of bismaleimide crosslinked network is believed to improve the toughness, reduce the moisture sensitivity and improve the dielectric properties of the bismaleimide thermoset without a sacrifice in heat resistance. 

Thus, several properties of the common bisphenol A-diglycidyl ether-based epoxy thermosets can be improved by cocuring with a commercial bisphenol A-dicyanate ester, and the blend is more cost-effective than the cyanate ester alone. Such epoxy/cyanate ester thermoset blends exhibit improvements in processability, toughness, hot-wet performance, and low dielectric properties. 

Bershtein VA, Egorova LM, Ryzhov VP, Yakushev PN, Fainleib AM, Shantalii TA and Pissis P (2001) Structure and segmental dynamics heterogeneity in hybrid polycyanurate-polyurethane networks, JMacromol Sci Phys, B 40 105-131. Srichatrapimuk V.W.and Cooper S.L.,. J. Macromol. Sci.-Phys., B15, 267 (1978). Bellamy LJ. The Infra-Red Spectra of Complex Molecules. Wiley, New York, 1954. Vilensky V A, Fainleib A M, Goncharenko L A and Danilenko I Yu (2002) Influenee of inclusion polymer and components thermodynamic affinity on bisphenol A dicyanate ester polycyclotrimerization. Reports of the National Academy of Sciences of Ukrainem-. A2- A%. 

Vilensky V A, Fainleib A M, Goncharenko L A and Danilenko I Yu (2002) Influence of inclusion polymer and components thermodynamic affinity on bisphenol A dicyanate ester polycyclotrimerization, Reports Natl Acad Sci Ukraine Nl 142-148 (in Russian). 

This paper presents the curing of bisphenol M dicyanate ester under nanoscale constraint. The effects of pore size and pore surface chemistty on the evolution of glass transition temperature of polycyanurate netwoiks are investigated and both are found to have a significant effect on the curing behavior and final Tf. Nanoconfinement accelerates the cure of bisphenol M dicyanate. For the unsilanized CPG, both the nanoconfinement and surface effects are observed whereas for the silanized controlled pore glass, only the nanoconfinement effect is present. FTIR study confirms the full conversion of the polycyanurate networks under nanoscale confinement. 

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