The renewable triphenols, resveratrol and dihydroresveratrol, were used in the preparation of two new phthalonitrile resins (PN), each containing three phthalonitrile groups. These are the first reported PN resins generated from a renewable feedstock. These amorphous PN resins were characterized thoroughly by DSC, NMR spectroscopy and rheometry. The monomers exhibited excellent rheometric viscosities suitable for resin transfer molding and resin infusion molding. After complete cure, the PN polymers exhibited thermal stability to above 500 8C and no glass transition temperature (T g ). As a result of the highly cross-linked nature of the network, these materials exhibited a low water uptake of 1 AE 0.2 % and dielectric constant values of approximately 3.0. These results suggest that resveratrol-derived PN resins are excellent candidates for use in maritime environments and aerospace applications.[a] Dr.
Two new oligomeric sulfone and sulfone-ketone containing phthalonitrile (PN) resins with excellent processability have been developed. The PN monomers were prepared from the reaction of an excess amount of bisphenol S with 4-(chlorophenyl)sulfone or 4,4-dichlorobenzophenone in the presence of a base in a solvent mixture (dimethylsulfoxide/toluene), followed by end-capping with 4-nitro-PN in a two-step, one-pot reaction. These PN resins exhibited good viscosities and cure times for molding into various shapes. After being thermally cured to yield crosslinked polymers, these polymers demonstrated superb mechanical properties, thermo-oxidative stability, and maintained good dielectric properties. Published 2016.† J. Polym. Sci., Part A:Polym.
The sustainable resveratrol-based phthalonitrile was used in the preparation of E-glass fiber-reinforced phthalonitrile composite panels fabricated by hot pressed prepreg consolidation with bis[4-(3-aminophenoxy)phenyl]sulfone (m-BAPS) as the curing additive. This amorphous monomer exhibited excellent viscosities at temperatures below 200 8C, which is applicable to standard processing conditions. Rheometric measurements were used to evaluate the cure of the composite as a function of the postcure conditions. The composite retains >95% of its room temperature storage modulus up to 450 8C based on these postcuring parameters. More importantly, flammability performance of the composite-which was determined in terms of ignitability, heat release, and mass loss rate-excels over other state-of-the-art polymer/glass composites. Even under the most extreme heat fluxes (e.g., 100 kWÁm 22 ), the composite performs exceptionally well suggesting that resveratrol-based phthalonitrile composites can be used in fire-resistant applications.
A method to improve the mechanical properties of phthalonitrile (PN) resins at lower postcure temperatures is achieved by blending a second‐generation oligomeric aromatic ether ketone‐based PN resin with 1,1,1‐tris‐[4‐(3,4‐dicyanophenoxy)phenyl]ethane in varying concentrations. Most of the mixtures exhibit a single softening temperature indicating that the two resins are miscibile in one another at the respective concentrations. After various blends are thermally cured to several postcure temperatures yielding crosslinked polymers, the polymers demonstrate superb mechanical properties and thermooxidative stability at lower overall postcure temperatures.
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