The macromolecular structure of coal

Coals are considered to be three-dimensionally covalently crosslinked macromolecular networks. Solvent swelling techniques, modem polymer theories, and regular solution theory are applied to two bituminous coals in an effort to estimate their crosslink densities. The coals are observed to be extensively, internally hydrogen bonded. The hydrogen bonds serve as crosslinks between the macromolecular chains and contribute substantially to the structural integrity of the coals. Both coals obey the predictions of regular solution theory and their nonpolar solubility parameters (δ) are estimated to be 9.5 (cal/cm³)^½ Flory interaction parameters (χ) were calculated for a series of nonpolar solvent-coal pairs. The Flory-Rehner and Kovac equations were then applied to the available data to estimate the crosslink densities of the coals.