Alexander V. Babkin

Phthalonitrile-carbon fiber composites produced by vacuum infusion process

High-temperature carbon fiber-reinforced plastics based on phthalonitrile resins are obtained for the first time by vacuum infusion process. For this purpose, formulations based on low-melting bis(3-(3,4-dicyanophenoxy)phenyl) phenyl phosphate monomer in combination with 1,3-bis(3,4-dicyanophenoxy)benzene and 4-[3-(prop-2-yn-1-yloxy)phenoxy]benzene-1,2-dicarbonitrile were developed. Resin viscosities η ≤ 600 mPa·s were suitable for VIP and at the same time the thermal and mechanical properties of the cured matrices were in high level featured to phthalonitriles (HDT ≥ 420℃, E ≥ 5.1 GPa). CFRP samples were manufactured by vacuum infusion process with carbon fabric and demonstrated thermal stability over 400℃ and a change of mechanical properties by less than 10% at 300℃. Present results sufficiently extend the application field of phthalonitriles as matrices for complex-shape high temperature composite parts in aerospace or high-temperature composite tooling for PEEK-like thermoplastics processing.

Mechanical and physicochemical properties of matrices for fiber reinforced plastics based on low-melting phthalonitrile monomers

The mechanical properties of cured phthalonitrile matrices for fiber reinforced plastics (FRP) based on low-melting phenylmethylsilanediyl-bis[oxymethylene(1,4-phenylene-4’-oxyphthalodinitrile)] (1) or its mixture with 1,3-phenylene-bis(oxy-4-phthalodinitrile) (2, comonomer) were studied. The flexural strength, Young’s modulus, fracture toughness, and some other characteristics of the cured resins based on monomer 1 (PN-1) and the mixture of monomers 1 and 2 (PN-1m) were determined. It is noted that the PN-1 resin can be processed by vacuum infusion and the PN-1m resin can be processed by compression injection molding. The developed resins are promising as materials for high-tech aerospace applications.

Thermally stable phthalonitrile matrixes containing siloxane fragments

New low-melting phthalonitrile monomers suitable for the production of high-temperature matrixes for polymer composite materials are synthesized. After the introduction of siloxane bridges into a monomer, the glass-transition temperature decreases to–1–27°С, depending on the type of substituent at the silicon atom. These compounds are found to be sufficiently hydrolytically stable, despite the presence of sensitive siloxane bonds. The cured resin retain properties featured to the class of phthalonitriles, such as a high onset tеmperature of degradation (>530°С in argon), a high heat deflection temperature (>420°С), and char yield. The considered compounds make it possible to widen the temperature window for processing of phthalonitrile resins without any change in the properties of the final material.

Dynamic and Static Mechanical Properties of Crosslinked Polymer Matrices: Multiscale Simulations and Experiments

We studied the static and dynamic mechanical properties of crosslinked polymer matrices using multiscale simulations and experiments. We continued to develop the multiscale methodology for generating atomistic polymer networks, and applied it to the case of phthalonitrile resin. The mechanical properties of the resulting networks were analyzed using atomistic molecular dynamics (MD) and dissipative particle dynamics (DPD). The Young’s and storage moduli increased with conversion, due both to the appearance of a network of covalent bonds, and to freezing of degrees of freedom and lowering of the glass transition temperature during crosslinking. The simulations’ data showed good quantitative agreement with experimental dynamic mechanical analysis measurements at temperatures below the glass transition. The data obtained in MD and DPD simulations at elevated temperatures were conformable. This makes it possible to use the suggested approach for the prediction of mechanical properties of a broad range of polymer matrices, including ones with high structural heterogeneity.