An emulsion explosive is a water-in-oil (W/O) emulsion: a supersaturated ammonium nitrate solution is dispersed as micron-sized droplets inside a continuous fuel-oil phase, and an emulsifier — most often a PIBSA-based polymeric surfactant — keeps that structure stable. Until the matrix is sensitized at the blast site, it is not an explosive at all; it ships as an oxidizer.
Written for the formulators and procurement teams who buy this chemistry. The real procurement risk is silent aging: crystallization and heat destroy stability long before anything looks wrong.
What actually holds an emulsion explosive together?
An emulsifier — and nothing else. A supersaturated oxidizer solution, mainly ammonium nitrate, is dispersed as micron-sized droplets in a continuous fuel phase of oil and wax — a thermodynamically unstable structure. The emulsifier sits at the droplet interface — one end in the oil, the other reaching into the salt solution — forming a film that keeps droplets fine and discrete.
Because the matrix cannot be initiated until it is sensitized in the borehole, it travels as an oxidizer (UN 3375, Class 5.1) rather than a Class 1 explosive — the basis of the bulk delivery model standard across the mining industry.
Why did PIBSA-based emulsifiers become the industry default?
Because a polymeric emulsifier holds this emulsion better than a small-molecule one — against textbook selection logic. PIBSA is an amphiphile built for the job: a long polyisobutylene tail dissolved in the fuel phase, carrying a reactive succinic-anhydride head anchored into the oxidizer droplets.
Comparative studies found polymeric emulsifiers outperformed low-molecular-weight agents such as sorbitan esters — despite producing higher interfacial tension. HLB, the classic selection number, correlated poorly with actual stability; head-group design mattered more. Process route counts too: thermal-process PIBSA contains no residual chlorine, unlike the chlorination route.
PIBSA also heads the ashless dispersant family in engine oils — that lubricant grade lives on our polyisobutylene succinic anhydride page.
How does an emulsion matrix fail in storage or heat?
Not by creaming — the dominant failure mode is the oxidizer salt crystallizing inside its own droplets. High-internal-phase emulsions resist flocculation; what degrades them is supersaturated ammonium nitrate crystallizing within the droplets, gradually turning the emulsion into a suspension.
Heat accelerates this: underground strata reach 40–50 °C, and even 2–3 hours at elevated temperature measurably reduced detonation velocity in tests. Contamination compounds it — Fe²⁺ ions lowered the decomposition onset from about 280 °C to about 271 °C and promoted crystallization. Finer droplets help: small, uniform droplets correlate with a higher storage modulus and higher detonation velocity.
So treat shelf-life claims as data requests: ask for temperature-resolved stability results and a droplet-size specification, not a generic “12 months” line.
From the labBuilding an emulsion or mining reagent? CheMost supplies the chemistry.View mining chemicalsWhat should you ask an emulsifier supplier?
For the spec sheet behind the marketing page — and the process route behind it. Six lines on a TDS carry most of the answer:
| Property | What it tells you | CheMost PIBSA1000 (typical) | Method |
|---|---|---|---|
| Acid value | Reactive head-group availability | 115 mgKOH/g | ASTM D664 |
| Viscosity at 100 °C | Pumping behavior | 650 mm²/s | ASTM D445 |
| Flash point | Safe handling margin | 220 °C | ASTM D93 |
| Density at 20 °C | Dosing logistics | 940 kg/m³ | ASTM D4052 |
| Water | Emulsion interference risk | 0.03% | ASTM D1744 |
| Mechanical impurities | Nozzle blockage risk | 0.02% | ASTM D2276 |
Confirm the process route and ask how the emulsifier behaves with your fuel phase and droplet-size target; indicative treat rate is about 1–2 wt% of the emulsion, and more is not automatically better. Use this list as incoming-QC acceptance criteria, with our PIBSA emulsifier for emulsion explosives as a concrete benchmark in the mining chemicals range.
Sourcing a PIBSA emulsifier? → Request a sample and TDS.
FAQ
What are the emulsifiers used in explosives?
Most modern emulsion explosives rely on PIBSA-based polymeric emulsifiers as the primary stabilizer; sorbitan esters such as sorbitan monooleate (SMO) appear mainly as co-emulsifiers fine-tuning droplet size.
What is the difference between ANFO and emulsion explosives?
ANFO is a dry blend of ammonium nitrate prills and fuel oil — cheap but not water-resistant, around 3,000 m/s; emulsions resist water and exceed 4,500 m/s.
What are bulk emulsion explosives?
Bulk emulsions are made as an unsensitized matrix at a plant, hauled as a Class 5.1 oxidizer, then pumped into boreholes and sensitized on site.
How are emulsion explosives manufactured?
At a product level: the oxidizer solution is emulsified into the fuel phase, and sensitization happens at the point of use. Detailed formulations and process parameters belong to licensed explosive manufacturers — outside this guide’s scope.
Can PIBSA be used alone, or is a co-emulsifier needed?
Both. PIBSA works standalone as the primary emulsifier or as the polymeric backbone of a blend, with a sorbitan-ester co-emulsifier tuning droplet size. Our explosives-grade PIBSA emulsifier is used both ways.
About This Guide
Prepared by CheMost’s technical support team from peer-reviewed literature and our own product data. CheMost supplies the PIBSA emulsifier, not finished explosives — classification and performance of a finished emulsion explosive belong to its formulator. Questions? Talk to our technical team.
References & Industry Standards
- Suda, K., Kramarczyk, B., et al. “Emulsion Explosives: A Tutorial Review.” Materials, 2022. PMC9318116
- Zhao, H.R., et al. “Advances in the Rheology of Emulsion Explosive.” Journal of Molecular Liquids, 2021. Summary via AZO Materials
- UNECE. European Agreement Concerning the International Carriage of Dangerous Goods by Road (ADR 2021).