Effects of Cross-Linking Degree and Characteristic Components on Mechanical Properties of Highly Cross-Linked Phenolic Resins: A Molecular Dynamics Simulation Study

Phenolic resins (PF), naphthol modified phenolic resins(NPF),and cyanate ester modified phenolic resins (CEPF) were constructedwhere naphthols and triazine rings act as chain reinforcing and chain-to-chainbridging roles, respectively. Then, molecular dynamics simulationswere performed to predict the Young's modulus. The resultsshow that methylene bridges and branched phenolic rings are key factorsaffecting the stiffness of resin. Introducing naphthols does not providea clear benefit in stiffness due to a counterbalance between the risein nonbonded energies and the drop in methylene bridges. For CEPF,the chain-to-chain bridges of triazine rings increase the Young'smodulus up to 2.93 GPa and contribute significantly to stiffness comparedto reinforcing chains by rigid naphthols. The trend of the three systemsfrom plastic to the cured state can be seen in the mean squared displacementand Young's modulus. These findings can support the study ofthe molecular design of PF to optimize stiffness.