DSC studies on long-term properties of nitrocellulose and SYM-diphenylurea system

Long-term investigations of the phase structure and pore structure of nitrocellulose and sym-diethyldiphenylurea (C1) mixtures were conducted for samples with C1 mass fractions w _C1=0.5, 0.6 and 0.8. The distribution of pore sizes and the composition of the nitrocellulose matrix were determined based on the melting enthalpy of C1. The three kinds of pores was observed with the characteristic size of about 7, 14 and 28 nm. Long-term storage of mixtures caused an increase in size of the smallest pores and a decrease of C1 concentration in the nitrocellulose matrix. The mechanism of changes in pore sizes is presented in term of multi-sheet model of NC fiber. This revised version was published online in July 2006 with corrections to the Cover Date.