Epoxy, cyanate ester-cured

A typical cured aerospace epoxy resin is highly cross-linked and may contain a dispersed nonpolar thermoplastic or rubber which reduces the equilibrium moisture content and hmits the reduction in Tg. As shown in Table 12.2, more advanced systems, such as an epoxy—cyanate ester blend, absorb lower concentrations of water at equilibrium. However, the water is not uniformly distributed so that the epoxy phase is stiU plasticised to the same extent. Figure 12.12 shows that the different component epoxies and/or hardeners are plasticised differentially with the development of additional relaxation peaks. We discussed the different degrees of water molecule hydrogen bonding as a function of network polarity in this chapter. 

Wu S J, Lin T K, Zhang J X and Shyu S S (2000) Properties of cyanate ester-cured epoxy/poly-phenylene oxide blends as a matrix material for Kevlar fiber composites, J Adhes Sci Technol 14 1423-1438. 

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... 

Su WFA (1993) Thermoplastic and thermoset main-chain liquid-crystal polymers prepared from biphenyl mesogen. J Polym Sci Polym Chem 31 3251-3256 Su WFA, Chuang CM (2002) Effects of chemical structure changes on curing reactions and thermal properties of cyanate ester-cured rigid-rod epoxy resins. J Appl Polym Sci 85 2419-2422... 

Experimentally a cyanate ester precursor mixture consisting of BPEC, 1 wt % BPE, and 100 ppm cobaltacetylacetonate was prepared and subsequently mixed with the cyclohexane phase separating solvent [86]. Essentially the same procedure as for the epoxy is used for sample preparation with the difference that the curing was done at 80 °C and post drying at 240 °C. 

Lin, C. H., Synthesis of novel phosphorus-containing cyanate esters and their curing reaction with epoxy resin, Polymer, 2004, 45, 7911-7926. 

The system has thus been reduced to a univariate problem and conventional analysis may be employed for subsequent quantification if required. In a closely related study of the curing of a cyanate ester rather than an epoxy resin (Cooper, 1999) a similar profile to Figure 3.46 was obtained after PCA (Figure 3.47), and a comparison with the univariate analysis of single peak intensities that are the major peaks in the first principal component after mean centring was made. 

Martin et al. (1989b) focus on cure of epoxies and cyanate ester resins for lamination of prepregs into multilayered circuit boards. The following dual Arrhenius engineering model was fitted to viscosity profiles ... 

Keywords. Cyanate ester, Polycyanurates, Phenolic-triazine, Polymer matrix composite, Cure kinetics, Polymer blends, Cyanate-epoxy blend, Bismaleimide-triazine resins, Aerospace structure... 

Despite their many attractive features, the search for further improvements in performance and reduction in cost of cyanate esters is never ending and a large number of studies have been devoted to matrix modification through blends, and co-curing of these systems. Reactions of cyanate esters with a variety of functional groups like amines [169], hydroxyl [34, 66], epoxy [170-172], phenols, etc., have been reported, among which the most studied are reactions with epoxy [173,174]. Epoxy-cyanate blends are common and found in many commercial and patented resin formulations. 

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