A study on the decomposition pathways of HTPB and HTPE pyrolysis by mass spectrometric analysis

Abstract

Hydroxyl-terminated polybutadiene (HTPB) and hydroxyl-terminated polyether (HTPE) are used as binders for rocket propellants, while the mechanisms for their pyrolysis processes are still not clear. In this work, the slow and fast pyrolysis behavior of HTPB and HTPE were studied with a combination of single photoionization mass spectrometry (SPI-MS) and GC-MS, respectively. SPI-MS allowed on-line studying the dynamics of volatile formation as a function of the pyrolysis process, and GC-MS was utilized to characterize the condensed products. Furthermore, the heavy products (m/z > 300) in the condensed liquids were also characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS). Based on the experimental results, a full picture of the product distributions from the HTPB and HTPE pyrolysis was described. Meanwhile, the decomposition pathways were proposed and discussed in detail. The results showed that the radical-addition reaction dominated the decomposition pathways of HTPB, in which the six-membered ring products were readily formed. HTPE was mainly transformed into ethers or aldehydes during the pyrolysis process, and the cyclic products were mainly composed of tetrahydrofuran and its derivatives.