Properties cyanate esters

The trimerization reaction of the polyfunctional cyanates is catalyzed by zinc or manganese octoate, copper carboxylates, and acetylacetonate metal chelates with a synergistic effect when the catalyst is mixed with 4-nonylphenol [21]. The final cure or postcure temperature depends on the glass transition temperature of the tridimensional network. This means that the semi-solid biscyanate 88 is cured at 180-195 C (Tg 192°C) while the biscyanate 85 is cured at 250-300°C (Tg 290°C). However, the maximum cure temperature can be reduced to 120°C in the former example by adding 6-10% of 4-nonylphenol. When compared to epoxies, cyanate esters have higher glass transition temperatures, better thermal stability, and improved dielectric properties. Cyanate esters have been primarily developed... 

Modified Bismaleimides. Bismaleknide resins may be further modified and blended with other thermoset resins or reactive diluents to achieve either specific end-use properties or processibiUty. Thermoset resins that can be used for modification are unsaturated polyesters, vinylesters, cyanate esters, and epoxies. 

The surface properties are of particular interest for composites and coatings. The n = 6 monomer will wet Teflon, and PTFE filled composites can be prepared. The critical surface tension of wetting for the fluoromethylene cyanate ester resin series has been determined from contact-angle measurements on cured resin surfaces. As indicated in Table 2.2, it parallels the fluorine composition and begins to approach the PTFE value of 18 dyn/cm. 

As indicated above, the dielectric properties are the chief consideration for applications of these fluoromethylene cyanate ester resins. As such, processing as coatings for microelectronic applications and as nonstructural castings and composites for radome-related applications is being investigated. In this respect the n = 6 system has been identified as the best compromise for synthesis, properties, and processing. Results in this section pertain only to this member of the series, which is currently under evahation for the above applications.13... 

The synthesis and properties of the fluoromethylene cyanate ester monomer series, NCOCH2(CF2) CH2OCN, n = 3, 4, 6, 8, 10, and corresponding resins... 

Materials Selection and Chemistry of Cyanate Ester Resins Morphology, Thermal and Dielectric Properties. ... 

Table 5. Molecular structure and properties of bisphenol-E cyanate ester resin (BPECN)...

Within the past several years, improvements in the toughening of high-temperature epoxies and other reactive thermosets, such as cyanate esters and bismaleimides, have been accomplished through the incorporation of engineering thermoplastics. Additions of poly(arylene ether ketone) or PEK and poly(aryl ether sulfone) or PES have been found to improve fracture toughness. Direct addition of these thermoplastics generally improves fracture toughness but results in decreased tensile properties and reduced chemical resistance. 

Ganguli, S. Dean, D. Derrick, J. Kelvin, P. Price, G. Vaia, R. Mechanical properties of intercalated cyanate ester-layered silicate nanocomposites. Polymer 2003, 44 (4), 1315-1319. 

Property Epoxy Phenolic Toughened BMI Cyanate ester... 

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. 

Although a large variety of such experimental cyanate esters have been reported, few have achieved commercial success. Some of these have been listed in Table 2 along with their key properties. The properties are very much dependent on the backbone. Thus, the experimental CE resin XU.71787 developed by Dow... 

Table 2. Commercial cyanate esters and thei monomer and polymer Properties ( ) ...

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