Synthesis and properties of novel 4,4′-biphenylene-bridged flame-retardant cyanate ester resin

Calixarene–based cyanate ester resin for high-temperature material

p-tert-Butylcalix[4]arene-derived cyanate ester resins, both single and binary systems, were synthesized and studied for their thermal properties. The results showed that pure calixarene cyanate ester can be thermally cured at comparatively high temperature, which remains in original powder state after thermally cured. So the pure calixarene cyanate ester resin fails to meet the processing demands of resin-matrixed composite. In this work, p-tert-butylcalix[4]arene cyanate ester was chemically functionalized to have highly decreased thermal cure temperature (by copolymerization with epoxy, bisphenol A cyanate ester (BPACE), and polysilazane (PSZ), respectively). The binary resins were thermally cured into monolithic materials. The optimal acceleration of thermal cure reaction was achieved with an addition of 10% PSZ. The addition of epoxy resin decreased thermal resistance and carbon yield of p-tert-butylcalix[4]arene cyanate ester and addition of BPACE slightly decreased thermal resistance and carbon yield, while PSZ highly improved thermal resistance and carbon yield. Glass transition temperature of the co-cured resin of calixarene cyanate ester with 10% PSZ was much higher than that of conventional BPACE. Calixarene cyanate ester possesses much better property than that of conventional BPACE resin.

Synthesis, characterization, and cure chemistry of high performance phosphate cyanate ester resins

Three thermosetting cyanate ester resins with phosphate cores and potential fire-resistant applications have been synthesized and characterized. A trifunctional resin studied in this work (PhosCy3) has a T_g > 360 °C and a char yield of 67% in air.

Synergistic physical properties of cocured networks formed from di- and tricyanate esters

The co-cyclotrimerization of two tricyanate ester monomers, Primaset PT-30 and 1,2,3-tris(4-cyanato)propane (FlexCy) in equal parts by weight with Primaset LECy, a liquid dicyanate ester, was investigated for the purpose of exploring synergistic performance benefits. The monomer mixtures formed stable, homogeneous blends that remained in the supercooled liquid state for long periods at room temperature, thereby providing many of the processing advantages of LECy in combination with significantly higher glass transition temperatures (315-360 °C at full cure) due to the presence of the tricyanate-derived segments in the conetwork. Interestingly, the glass transition temperatures of the conetworks after cure at 210 °C, at full cure, and after immersion in 85 °C water for 96 h were all higher than predicted by the Flory-Fox equation, most significantly for the samples immersed in hot water. Conetworks comprising equal parts by weight of PT-30 and LECy retained a "wet" glass transition temperature near 270 °C. The onset of thermochemical degradation for conetworks was dominated by that of the thermally less stable component, while char yields after the initial degradation step were close to values predicted by a linear rule of mixtures. Values for moisture uptake and density in the conetworks also showed behavior that was not clearly different from a linear rule of mixtures. An analysis of the flexural properties of catalyzed versions of these conetworks revealed that, when cured under the same conditions, conetworks containing 50 wt % PT-30 and 50 wt % LECy exhibited higher modulus than networks containing only LECy while conetworks containing 50 wt % FlexCy and 50 wt % LECy exhibited a lower modulus but significantly higher flexural strength and strain to failure. Thus, in the case of "FlexCy", LECy was copolymerized with a tricyanate that provided both improved toughness and a higher glass transition temperature.

Cyanate ester resins containing pentadecyl-substituted cyclohexyl moiety: Synthesis, curing and structure–property relationship

Cyanate ester (CE) monomers containing pentadecyl-substituted cyclohexyl moieties such as 1,1-bis(4-cyanatophenyl) 3-pentadecylcyclohexane and 1,1-bis(4-cyanatophenyl) cyclohexane were synthesized and characterized by Fourier transform infrared, proton-nuclear magnetic resonance (1H-NMR) and carbon-nuclear magnetic resonance (13C-NMR) spectroscopies as well as differential scanning calorimetry (DSC). Both 1,1-bis(4-cyanatophenyl) 3-pentadecylcyclohexane and 1,1-bis(4-cyanatophenyl) cyclohexane exhibited better processability coupled with lower melting points, lower cure onset with broad cure exotherm than the commercially available CE monomer, namely, 2,2-bis(4-cyanatophenyl) propane. Glass transition temperatures of cured 2,2-bis(4-cyanatophenyl) propane, 1,1-bis(4-cyanatophenyl) cyclohexane and 1,1-bis(4-cyanatophenyl) 3-pentadecylcyclohexane were observed to be 288°C, 302°C and 160°C, respectively. Cured 1,1-bis(4-cyanatophenyl) cyclohexane displayed higher storage modulus (1.59 × 10 9 Pa) than 1,1-bis(4-cyanatophenyl) 3-pentadecylcyclohexane (1.07 × 10 9 Pa) and 2,2-bis(4-cyanatophenyl) propane (1.39 × 10 9 Pa). The order of thermal stability of cured polycyanurates was found to be 2,2-bis(4-cyanatophenyl) propane > 1,1-bis(4-cyanatophenyl)cyclohexane > 1,1-bis(4-cyanato phenyl) 3-pentadecylcyclohexane. The moisture absorption of cured resins derived from 1,1-bis(4-cyanatophenyl) 3-pentadecyl cyclohexane and 1,1-bis(4-cynatophenyl)cyclohexane was found to be lower than that of 2,2-bis(4-cynatophenyl) propane implying the role of pentadecyl substituent and/or cyclohexyl moiety in imparting hydrophobicity to the polycyanurates.