A series of renewable bis(cyanate) esters have been prepared from bisphenols synthesized by condensation of 2-methoxy-4-methylphenol (creosol) with formaldehyde, acetaldehyde, and propionaldehyde. The cyanate esters have been fully characterized by infrared spectroscopy, (1)H and (13)C NMR spectroscopy, and single crystal X-ray diffraction. These compounds melt from 88 to 143 °C, while cured resins have glass transition temperatures from 219 to 248 °C, water uptake (96 h, 85 °C immersion) in the range of 2.05-3.21%, and wet glass transition temperatures from 174 to 193 °C. These properties suggest that creosol-derived cyanate esters may be useful for a wide variety of military and commercial applications. The cure chemistry of the cyanate esters has been studied with FTIR spectroscopy and differential scanning calorimetry. The results show that cyanate esters with more sterically demanding bridging groups cure more slowly, but also more completely than those with a bridging methylene group. In addition to the structural differences, the purity of the cyanate esters has a significant effect on both the cure chemistry and final Tg of the materials. In some cases, post-cure of the resins at 350 °C resulted in significant decomposition and off-gassing, but cure protocols that terminated at 250-300 °C generated void-free resin pucks without degradation. Thermogravimetric analysis revealed that cured resins were stable up to 400 °C and then rapidly degraded. TGA/FTIR and mass spectrometry results showed that the resins decomposed to phenols, isocyanic acid, and secondary decomposition products, including CO2. Char yields of cured resins under N2 ranged from 27 to 35%, while char yields in air ranged from 8 to 11%. These data suggest that resins of this type may potentially be recycled to parent phenols, creosol, and other alkylated creosols by pyrolysis in the presence of excess water vapor. The ability to synthesize these high temperature resins from a phenol (creosol) that can be derived from lignin, coupled with the potential to recycle the composites, provides a possible route to the production of sustainable, high-performance, thermosetting resins with reduced environmental impact.

The low-temperature properties of high-density terpene dimer fuels and fuel mixtures with JP-8, JP-10, and hydrogenated pinene have been studied by shear viscometry and thermomechanical analysis (TMA). Neat terpene dimers have a viscosity of 3.94 × 10 3 mPa•s at −10 °C, while 50:50 mixtures with JP-10, RJ-4, pinane, and JP-8 have viscosities 2−3 orders of magnitude lower at 23.9, 53.0, 24.9, and 3.7 mPa•s, respectively. Linear and branched alkanes in JP-8 disrupt glass formation of the dimers, explaining the significant difference between the viscosity afforded by bicyclic diluents and JP-8. To complement the viscosity data, TMA was used to observe low-temperature transitions (T m and T g ) of the blended fuels. Mixtures of the terpene dimers with cyclic molecules show only glass transition temperatures with no observable melting points, while mixtures with JP-8 and decane show T g values that transition to melting points at high concentrations of terpene dimers. The results suggest that blending conventional fuels with terpene dimers is an effective strategy for mitigating the high viscosity of the C20 molecules. In addition, blending these renewable fuels with conventional jet fuel (JP-8) imparts both a higher density as well as an improved volumetric net heat of combustion while maintaining an acceptable low-temperature viscosity when compared to JP-8 alone.

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