Investigating the plateau burning of composite solid rocket propellants based on different isocyanates

摘要

Plateau burning of composite solid rocket propellants is a required goal in the design of propulsion systems for space launching vehicles and military missiles. In this study, we aimed to generate plateau burning from abundant and processing-friendly curing agents. Therefore, three propellant compositions were prepared based on changing the employed isocyanate namely, hexa-methylene di-isocyanate (HMDI), iso-phorone di-isocyanate (IPDI) and di-cyclohyxyl-methane di-isocyanate (H_(12)MDI) to investigate their ability to generate plateau burning. The burning rate of these compositions was measured at 1 MPa-intervals from 1-14 MPa via Crawford bomb to study its response to different pressure regions. While compositions based on HMDI and IPDl exhibited bi-plateau and plateau burning phenomena respectively, the H_(I2)MD1 composition did not show any abnormal behaviour at the examined pressure range. These results are related to the activation energy of the first decomposition stage of the employed binders, which is believed to be responsible for the existence of the plateau burning. The higher the decomposition activation energy of the binder was found to absorb more energy from the surrounding burning surface, thus causing less thermal energy to be delivered to the coarse ammonium perchlorate to burn. This would cause a slight depression in the structure of the flame of coarse ammonium perchlorate consequently causing the plateau burning to exist.