Decomposition Kinetics of Azodicarbonamide in Pine Fiber–Polypropylene Composites Using a Capillary Rheometer

ABSTRACT This study investigates the decomposition kinetics of azodicarbonamide (ACA) as a chemical blowing agent (1 wt%) in polypropylene composites with varying pine fiber concentrations (5, 10, and 15 wt%). The thermal decomposition curves of azodicarbonamide were determined using a capillary rheometer, which served as a batch reactor to measure pressure and temperature as a function of time. To obtain all the information, tests were performed on neat polypropylene, polypropylene/pine fiber composites, and polypropylene/pine fiber composites containing ACA. The results showed that a higher fiber content resulted in increased pressure generated due to the release of volatiles (humidity and extractives) by the fibers. However, the addition of the ACA significantly increased the pressure due to gas generation from its decomposition. Taking all the effects into account, the experimental data were well fitted to the Kamal–Sourour kinetics equation. Then, the kinetic parameters of ACA decomposition were used to determine that the overall reaction order is 1.5. Finally, 10% pine fiber was shown to decrease the activation energy of its autocatalytic reaction and produce foamed samples with a high number of small and uniform cells.