Computational and Experimental Study of Phenolic Resins: Thermal-Mechanical Properties and the Role of Hydrogen Bonding

Molecular dynamics simulations and experimental measurements were used to investigate the thermal and mechanical properties of cross-linked phenolic resins as a function of the degree of cross-linking, the chain motif (ortho-ortho versus ortho-para), and the chain length. The chain motif influenced the type (interchain or intrachain) as well as the amount of hydrogen bonding. Ortho-ortho chains favored internal hydrogen bonding whereas ortho-para favored hydrogen bonding between chains. Un-cross-linked ortho para systems formed percolating 3D networks of hydrogen bonds, behaving effectively as hydrogen gels. This resulted in differing thermal and mechanical properties for these systems. As cross-linking increased, the chain motif, chain length, and hydrogen bonding networks became less important. Elastic moduli, thermal conductivity, and glass transition temperatures were characterized as a function of cross-linking and temperature. Both our own experimental data and literature values were used to validate our simulation results.