For many years, the production of plastic-bonded high explosives (PBXs) has relied on manufacturing methods that have changed very little.
While these techniques have worked for decades, they can be difficult to control and often produce inconsistent results.
Now, researchers at Lawrence Livermore National Laboratory (LLNL) have developed a new approach that could make the manufacturing process safer, more reliable, and easier to scale up.
The study, published in Propellants, Explosives, and Pyrotechnics, focuses on improving how small pellets, known as prills, are made.
These pellets are an important part of producing plastic-bonded high explosives, which are widely used in specialized defense applications.
In the traditional manufacturing process, explosive crystals are mixed with a polymer binder, a material that holds the particles together. This mixture forms small granules that are later compressed into solid parts.
However, the process is sensitive to small changes, meaning two production batches can behave slightly differently.
That inconsistency is a problem because the final material’s performance depends not only on its chemical ingredients but also on the size, shape, and internal structure of the tiny particles.
To solve this challenge, LLNL researchers launched Project MAHEM, short for A Modern Approach to High Explosive Manufacturing.
The goal is to better understand how manufacturing methods affect the final product and to borrow proven technologies from industries such as pharmaceuticals and food production, where strict quality control is already standard.
For this study, the team tested a process called extrusion-spheronization, which is commonly used to produce uniform medicine pellets. Instead of relying on older manufacturing methods, the researchers adapted this technology to create highly consistent explosive-like pellets.
To improve safety during the experiments, the team used a formulation containing mostly an insensitive high explosive combined with a small amount of polymer binder. This reduced the risk while allowing them to study the manufacturing process.
The material was first mixed into a soft, damp consistency before being pushed through an extruder to create thin strands. These strands were then placed inside a spinning machine, where they rolled into smooth, nearly round pellets.
The researchers carefully examined the finished pellets using advanced imaging tools to study their size, shape, surface, and internal structure. They then compressed the pellets into test samples and measured their strength and density.
The results showed that the new process produced pellets much more consistently than traditional methods. While different solvent mixtures had some effect, the researchers found that the size and shape of the pellets played the biggest role in determining the strength of the finished material.
The team also looked for ways to improve worker safety. The current experimental process still requires several manual steps, meaning researchers must repeatedly enter and leave specialized rooms where energetic materials are handled.
To address this, engineering students at the University of California, Santa Barbara designed an automated version of the manufacturing system. Their award-winning machine reduced the need for manual handling while producing pellets of similar quality.
Automation could bring important safety benefits by reducing the amount of time workers spend around hazardous materials while also increasing production efficiency.
Although more work is needed before the technology is used on a larger scale, the researchers believe this modern manufacturing method could replace decades-old techniques with a more predictable, efficient, and safer process.
The project highlights how ideas from other industries can help improve even the most specialized manufacturing fields.
