Phenylphosphine Oxide Catalysis of Epoxy Polymerization

Document Type

Conference Proceeding

Publication Date

1-1-2020

School

Polymer Science and Engineering

Abstract

Atomic oxygen (AO) attack to carbon-fiber reinforcing polymers (CFRP's) on spacecraft surfaces in low earth orbit (LEO) threatens spacecraft safe operation and service life. Incorporating phenylphosphine oxide (PPO) groups into epoxies has been shown to offer a self-regenerating method of protection from AO, but has catalytic effects on the polymerization reaction of epoxies. Herein, epoxides and diamines containing PPO groups were synthesized and the reactivity of the prepared monomers was evaluated for shelf-life and workability. The catalytic effect of PPO on the epoxy polymerization was investigated via differential scanning calorimetry (DSC), rheokinetic evaluation, real-time Fourier-transfer infrared spectroscopy (FT-IR), and real-time heated 31P nuclear magnetic spectroscopy (NMR). The catalytic mechanism was further investigated through electron rich and electron deficient PPOs to elucidate the effect of aromatic substituents on the catalytic effect. It was found that the incorporation of electron rich phosphines had significant catalytic effects on the epoxy polymerization, shifting the onset of polymerization earlier by 50 °C. Moreover, the material remains processable as evaluated by rheology and a mechanism for the catalytic reaction is proposed. This work builds upon previously reported research to fully evaluate PPO epoxies and furthermore suggests that PPO epoxies are excellent candidates for AO resistant CFRPs.

Publication Title

Composites and Advanced Materials Expo, CAMX 2020

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