Interfacial shear strength of a cured vinyl ester resin at graphene sheets from molecular dynamics simulations Conference Paper uri icon

abstract

  • Interfacial adhesion between graphene sheets and a cured vinyl ester (VE) resin was calculated using molecular dynamics (MD) simulations. The formation of a polymer or resin interphase at and near carbon surfaces is a key issue because an interphase can modify carbon/resin interfacial bonding, which determines the load transfer capability between the matrix and the carbon reinforcement. In this work, an advanced, chemically realistic approach was used to create that resin/carbon interfacial region. First, a model 33 wt% styrene containing liquid VE resin was equilibrated in the presence of pristine graphene surfaces to determine the gradient of monomers that forms as a function of the distance from the surface into the bulk region. The monomer composition present at the surface differs from that from in the bulk, leading to the formation of a monomer mole ratio gradient versus distance from the surface. This equilibrated monomer distribution was then cured by applying the Relative Reactivity Volume (RRV) curing algorithm to form a crosslinked VE resin while enforcing the correct regiochemistry and relative reactivity ratios within the simulated free radical addition polymerization cure. The curing resin/monomer system was regularly equilibrated during the cure, allowing the graphene surface to influence the cure. This procedure produces a cured resin composition adjacent to the surface with a unique composition different than that of the bulk resin. The resin/graphene interfacial shear strength will be different than if the bulk resin's structure was adjacent to the graphene. The concentration of styrene in both the equilibrated liquid monomers and the cured VE resin was substantially higher near the pristine graphene sheets than in the bulk, affecting both the interfacial shear strength and near surface crosslink density. After crosslinking, the resin's glass transition temperature in the graphene/cured VE repeating unit cell was 466 K - 502 K. This is 50 to 100 K higher than for the pure VE matrix. The resin/graphene calculated interfacial shear strength was 118 MPa, indicating effective stress transfer from the VE matrix to the graphene sheets. This simulation protocol provides a more realistic approach to the use of MD simulations to predict the interfacial adhesion of any resin/reinforcement surface than has been reported previously.

author list (cited authors)

  • Jang, C., Lacy, T. E., Gwaltney, S. R., Tohigani, H., & Pittman, C. U.

publication date

  • December 2012