Degradation of cellulose esters during aging and processing measured by gel permeation chromatography

Cellulose esters are degraded by thermal and mechanical stress resulting in a decrease of the mean molar masses M sub N (number average), M sub W (mass average) and M sub Z (Z-average). These mean values are calculated from the molar mass distributions (MMD), which were measured by gel permeation chromatography (GPC) for cellulose nitrate and cellulose acetate containing samples. These mean values characterize the MMD in the low. (M sub N), medium (M sub W) and high (M sub Z) molecular mass regions. Cellulose nitrate (nitrocellulose, NC) is sensitive to thermal stress and to guarantee the service and security lifetimes of NC-based propellants high requirements are imposed on its chemical stability. Besides the older testing methods e.g. weight loss, recently the determination of the stabilizer consumption and of the decrease of the molar masses as a function of storage time and storage temperature are used to judge the chemical and mechanical stabillity /1,2,3/.