Reaction Induced Phase Separation and Molecular Weight Dependence of Thermoplastic Toughened Epoxy Networks and Validation With Molecular Simulation

Thermoplastic toughened epoxy systems are widely utilized for their excellent strength and performance to weight ratios. However, understanding phase separation and the ability to direct resulting morphologies is crucial to achieving optimal performance. This research investigates the molecular weight dependence on reaction induced phase separation (RIPS) of high Tg thermoplastic filled epoxy networks that occurs during network cure and how atomistic molecular dynamics (MD) simulations can be utilized to validate results. The dissolution of thermoplastic into epoxy and pre-polymer conversion are simultaneously achieved through use of a high shear continuous reactor. While molecular weight of the thermoplastic drives solubility and phase separation, and the loss of solubility of the thermoplastic within the epoxy prepolymer initiates phase separation. It is hypothesized that the relative time until gelation and specific viscosity environment determines the development of final morphology, and can be directed. Co-continuous and dispersed droplet morphologies are targeted by adjusting the thermoplastic loading levels. Evaluation and characterization of final morphology type and domain size will be performed SEM. In addition to morphology characterization, samples are monitored during cure for rheological evidence of phase separation. Molecular dynamics (MD) simulations will be used to validate results. The effects of molecular weight and rheological changes during cure on network morphology will be resolved using molecular simulations to validate experimental results, establishing tunable and controlled phase separation for targeted morphologies