Transitions and relaxations in plasticised nitrocellulose

Abstract

Mixtures of nitrocellulose (NC) and various plasticisers were studied by dynamic mechanical analysis (d.m.a.) and differential scanning calorimetry (d.s.c.). The plasticisers were nitroglycerine, triacetin, diethylene glycol dinitrate and dimethylacetamide. At high plasticiser concentrations a single glass transition was observed. However, at lower plasticiser concentrations the glass transition split into two processes: a low temperature transition associated with the glass transition of the plasticiser, and a higher temperature loss process associated with the NC. The splitting of the glass transition was attributed to a breakdown in the cooperativity of motion of the plasticiser and NC molecules. An additional transition of a different type occurred at about 50°C. This transition temperature was independent of plasticiser type and concentration, and of the d.m.a. measuring frequency. It was accompanied by an endothermic peak in d.s.c. traces and was attributed to an increase in flexibility of the NC molecule.