# Biodegradability of Binder System Waste from Hydroxyl-Terminated Polybutadiene Propellant and Pretreatment for Biodegradation

## TL;DR

This study explores how waste from HTPB propellant can be broken down by microbes and improves the process using chemical pretreatment.

## Contribution

The study introduces a pretreatment method using sodium methoxide-methanol to enhance the biodegradability of HTPB propellant binder waste.

## Key findings

- The binder system film weight decreased by about 43% after 60 days of biodegradation.
- FT-IR analysis showed reduced C=O and C-O bond signals, indicating partial degradation.
- Pretreatment with sodium methoxide-methanol increased biodegradability of the binder system.

## Abstract

Large amounts of binder system waste are produced upon the recovery of energetic components in scrapped hydroxyl-terminated polybutadiene (HTPB) propellant. This study investigated the biodegradability of the binder system waste using a microbial enrichment solution as the biodegradation medium. We measured the binder system weight loss and performed Fourier-transform infrared (FT-IR), thermogravimetric (TG), and scanning electron microscopy (SEM) analyses of the binder system after 60 days of biodegradation. The results show the binder system film weight decreased by approximately 43% and stabilized after 50 days. The FT-IR analysis shows a reduction in C=O and C-O bond signals, whereas N-H, C-N, and C=C bond signals remain nearly unchanged. The TG analysis shows that the difference between the DOA weight in the initial film and that of the thermal decomposition was almost equal to the weight loss of the binder system film after biodegradation. The SEM analysis shows irregular pits on the film. The binder system has a certain biodegradability, which is mainly caused by its plasticizer component, i.e., DOA. HTPB-based polyurethane, the other major component, is difficult to degrade by microorganisms. As such, the binder system was pretreated with sodium methoxide-methanol solution as a depolymerization reagent, and the pretreated product yielded higher biodegradability.