A detailed parametric mapping analysis of the thermal expansion coefficient for isotropic polyoxymethylene is presented. The molecular composite model has been computerized to investigate the variation of the thermal expansivity of isotropic polyoxymethylene sheets with some typical morphological and structural parameters. The results are reported and analyzed in terms of three-dimensional structure-property maps. The thermal expansion coefficient is found to be significantly dependent on the crystallite content, in the first place, followed by the transverse aspect ratio of the crystallites and the amorphous phase stiffness. It is only at relatively low levels of crystallinity that the thermal expansivity is sensitive to the variation of the amorphous phase tensile modulus. The longitudinal aspect ratio is slightly effective in altering the expansion coefficient as long as it is kept below 25; otherwise it is ineffective.