Characterization and evaluation of TPU based compressible polymer bonded explosive and investigation of effects of pressing parameters on its properties

Date

2026-7-14

Author

Bozdemir, Alperen

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

80
views

0
downloads

Cite This

Pressable polymer-bonded explosive (PBX) systems require a careful balance among high solid loading, compact density, mechanical integrity, and processability. Binder characteristics, particle size distribution, and pressing conditions significantly affect particle packing, pressure transmission, and the quality of the final compact material. Consequently, a systematic understanding of formulation and processing variables is critical for achieving reproducible PBX compacts. This study investigated HMX–TPU-based pressable PBX formulations using a stepwise experimental approach. Initially, an inert model system facilitated the comparison of four binder candidates: TPU (Estane 5703), ACM (HyTemp 4454), FKM-A (Viton A), and FKM-B (Viton B). Hence, the evaluation criteria of this study include coating homogeneity, compact density, morphology, particle size similarity, flowability, and micromeritic behaviour. TPU binder demonstrated the most favourable overall performance, so it was selected for binder of subsequent energetic formulation. Moreover, in the energetic system, the reference composition consists of 93 wt.% HMX and 7 wt.% TPU binder. The effects of binder ratio, HMX particle size distribution, and pressing parameters were assessed using density measurements, indirect tensile strength determined by the Brazilian test, and fracture morphology of PBX compacts. Overall, results indicate that the bimodal B4/S20 mixture, composed of 80 wt.% coarse HMX Class 3 and 20 wt.% fine HMX Class 2, serves as an effective reference formulation for subsequent processing and modelling studies, with a density of 1.796 g/cm³ and 97.84% of the theoretical maximum density under initial evaluation conditions. Using this formulation, the influences of pressing pressure, temperature, dwell time, pressing speed, aspect ratio, and die-wall lubrication were systematically examined to enhance compact quality and elucidate the compaction behaviour of the PBX system. The investigation of pressing parameters revealed that pressures between 140 and 200 MPa, temperatures from 70 to 90 °C, dwell times of approximately 90 seconds, and low-to-moderate pressing speeds constitute an optimal processing window for producing dense and mechanically balanced PBX compacts. Furthermore, the effects of aspect ratio and die-wall friction were assessed using a pressure transmission approach, which demonstrated that lubrication enhances pressure transfer, while the absence of lubrication increases friction-related pressure losses. A first-order density prediction model based on effective pressure was also adapted for PBX compaction. This model estimated average compact density with prediction errors between 0.14% and 0.43%, supporting its value as a practical approximation for pressable PBX systems.

Subject Keywords

Pressable PBX, HMX, Estane 5703, PBX Compaction, Particle Packing, Density Prediction

URI

https://hdl.handle.net/11511/119942

Collections

Graduate School of Natural and Applied Sciences, Thesis