Calculation of crosslink density in short chain networks

Simple, new equations are provided for calculating crosslink density of networks prepared from low-molecular-weight, multi-functional reactants. The equations apply to stoichiometric mixtures at incomplete conversion and are obtained by modification of the Scanlan (Sc) equation. Previously the Sc equation was limited to complete conversion. Examples are selected to represent network forming reactions frequently encountered in thermoset industrial coatings. The rather complex Miller and Macosko (M and M) calculations are applied to the same examples. At extents of conversion in the 0.75 to 1.00 range, the modified Sc equations and the M and M calculations are shown to give the same results. The Sc equations account for dangling ends but neglect sol whereas the M and M calculations account for both dangling ends and sol. Clarifications are provided to explain inconsistencies in published values of 'number average molecular weight of network chains'. (C) 1997 Elsevier Science S.A.