Explosives & Energetic Materials
Why C-Therm Trident is Ideal for Explosives and Energetic Materials
C-Therm’s Modified Transient Plane Source (MTPS) method for measuring the thermal conductivity of explosives was developed in collaboration with the U.S. NAVSEA Surface Warfare Division and is purpose-built for testing energetics, ordnance, and propellants. The Trident uses MTPS technology to measure energetic materials with a single-sided sensor, delivering results in under three seconds.
Designed for Safety |
Small Sample Volume |
Sample Versatility |
Validate Thermal Models |
Why Thermal Conductivity Matters for Explosives and Energetic Materials
Every energetic material generates heat as it decomposes. Whether that heat escapes or accumulates depends in part on thermal conductivity (k), making it an important property for understanding thermal behaviour and assessing safe operating conditions.
That question applies across the forms energetic materials actually take: a cast propellant grain, a pressed pellet, a polymer-bonded charge, a stored emulsion, a packed pyrotechnic powder. In each case, the geometry and internal structure govern how far reaction heat must travel before it can be lost.
Thermal conductivity is used in:
- SADT and time-to-ignition predictions, where it influences how quickly reaction heat moves through the material.
- Critical dimension and thermal runaway modelling using approaches such as Frank-Kamenetskii theory.
- Slow and fast cook-off modelling, where thermal conductivity helps determine temperature gradients and the onset of reaction.
- Formulation and process development, where local heat build-up can affect mixing, casting, curing, drying, and machining.
Energetic formulations combine multiple components, binders, additives and void structures, so their effective thermal behaviour may differ significantly from that of the individual ingredients. Published values for a neat compound will not describe a filled, cured formulation.
Measuring the thermal conductivity of the actual formulation provides representative material data that supports thermal modelling, formulation development, and safety assessments.
Five Key Considerations When Testing Energetic Materials
Testing energetic materials requires careful control of the measurement conditions. The properties of the sample, the amount of material required, thermal exposure, power input, electrical configuration, and mechanical contact can all affect how a test is performed.
For applications involving explosives, propellants, and pyrotechnics, these considerations are particularly important when selecting and configuring a thermal measurement method. The following factors should be evaluated as part of the test setup:
- Sample volume
- Thermal exposure time
- Applied power
- Electrical grounding
- Contact pressure
Understanding these practical requirements before testing helps researchers establish an appropriate measurement approach while minimizing unnecessary sample handling and exposure.
In the short video, one of our subject matter experts discusses five key considerations to keep in mind when measuring the thermal conductivity of energetic materials.
Which Energetic Material Are You Characterizing?
Insensitive Munitions & Military Explosives
insensitive munitions · IM qualification · slow cook-off · fast cook-off · plastic-bonded explosive · PBX · HMX · RDX · NTO · cast-cured explosive · hot-spot desensitisation
Insensitive-munitions qualification asks a thermal question before it asks a mechanical one: when a munition is held in a slow-heating or fuel-fire environment, where does the charge reach reaction temperature first, and how long does it take? Answering that in simulation requires the thermal conductivity and volumetric heat capacity of the actual filled formulation, not of the neat energetic, binder loading, plasticiser content, aluminium addition and void fraction all shift the transport properties away from handbook values.
Cook-off test procedures such as STANAG 4382 (slow heating) and STANAG 4240 (fast heating / liquid fuel fire), and the hazard-assessment framework of MIL-STD-2105, define the experiment. The thermal model that predicts the outcome, and that reduces the number of expensive full-scale trials required, is only as good as the property data it is built on.
The MTPS sensor measures a cast or pressed face directly, so the same charge can be characterised before and after ageing or conditioning without being consumed.
C-4 plastic explosives
Solid Rocket Propellants & Aerospace Energetics
solid rocket propellant · composite propellant · HTPB binder · ammonium perchlorate · gun propellant · double-base propellant · burn-rate modelling · grain thermal profile
In a composite propellant grain, thermal conductivity governs the pre-heat zone ahead of the burning surface, the temperature profile through the grain during storage and conditioning, and the exotherm management problem during mixing and cure. It also determines how a grain responds to solar or aerodynamic heating in service.
Composite propellants are heavily filled, oxidiser loadings above 80% by weight are routine, so the effective conductivity of the formulation bears little relationship to the binder or the oxidiser alone. Filler dispersion, sedimentation and agglomeration all move the number, which is precisely why MTPS is useful as a formulation-development tool: it is sensitive to those effects and fast enough to screen a matrix of mixes in a single session.
C-Therm instruments are in service in aerospace propulsion laboratories including NASA.
Applications in aerospace energetics
Commercial Explosives, Ammonium Nitrate Emulsions & Mining
ammonium nitrate emulsion · ANE · bulk explosive · emulsion explosive · blasting agent · mining explosives · glass microballoons · sensitiser · ammonium nitrate storage
Bulk emulsion explosives are manufactured, pumped, stored and transported in large volumes, and a series of international incidents has kept the thermal decomposition behaviour of ammonium nitrate under regulatory attention. Storage limits, container sizing and transport classification all rest on thermal-stability assessment, and the conduction term in that assessment is thermal conductivity.
Emulsions are also the class of material that steady-state and flash methods handle worst. An ANE is a viscous, water-bearing, sensitiser-loaded system that cannot be machined into a specimen and should not be held at elevated temperature for hours. The MTPS Liquids & Powders Cell takes the emulsion as it is.
The Canadian Explosives Research Laboratory used exactly this approach to quantify how aluminium and glass-microballoon loading shift the conductivity of a commercial ANE.
Storage limits and transport classification for emulsion explosives rest on thermal-stability assessment, where thermal conductivity (k) is the conduction term.
Pyrotechnics, Thermites & Energetic Powders
pyrotechnics · thermite · energetic powder · flare and igniter composition · combustible dust · minimum ignition energy · dust explosion · powder handling safety · reactive metal powder
Pyrotechnic and thermite compositions are powder systems, and powder thermal conductivity is a function of the packing state as much as the chemistry: particle size, morphology, tap density and interstitial gas all move the result. Characterising them therefore means measuring the actual packed condition rather than deriving a value from constituent properties.
The same physics governs the combustible-dust hazard in mining, milling and grain handling. Adding inert solids to a combustible powder raises the minimum ignition energy — but the effect is threshold-driven, and the inert’s own thermal conductivity is a controlling variable in where that threshold sits.
The MTPS Liquids & Powders Cell holds a fixed volume with a defined tamping weight so packing is reproducible between measurements, which is what makes powder-to-powder comparison meaningful.
MTPS Liquids & Powders Cell with tamping weight: reproducible packing for powder-to-powder comparison
Thermal Conductivity for Process Safety
In a thermal hazard assessment, thermal conductivity is the property that decides whether decomposition heat escapes a mass of material or accumulates inside it. It sets the conduction term in every model that follows: hot-spot formation, thermal runaway, critical temperature, time to maximum rate, and the self-accelerating decomposition temperature (SADT) that determines how a self-reactive substance or organic peroxide may be stored and shipped.
It is also a process-dependent property. Thermal conductivity changes with temperature, pressure, density, compression and moisture, so a value measured under convenient laboratory conditions can misrepresent the same material as it is actually mixed, pressed, dried, stored or transported. Representative test conditions are what turn a thermal conductivity number into a usable input for thermal risk.
Prevent Heat Build-Up
Identify conditions where poor heat dissipation creates hot spots and thermal runaway risk. Measured thermal conductivity improves predictions of critical dimensions and safe charge mass.
Improve Scale-Up Confidence
Larger volumes retain heat differently than small samples. Measured thermal-property data helps translate bench-scale results to process scale and supports package-specific safety assessments.
Test at Temperature
Measure across relevant storage, processing, drying and decomposition temperatures. Automated Thermal Control covers ambient to 300 °C while the thermal chamber covers −73 °C to 200 °C.
Test Under Pressure & Compression
Confinement changes heat transport. The Trident supports testing up to 2000 psi and under controlled compression to characterise materials in their actual pressed, packed or confined states.
Test Real-World Sample Formats
Test emulsions, powders, pastes, liquids, cast and pressed solids, and polymer-bonded composites with minimal preparation and samples as small as 1.25 mL.
Better Data. Safer Decisions.
Measured thermal-property data supports better heat-transfer models, defensible operating limits and more confident process design, replacing estimated values with results measured to ASTM D7984.
A measured example: when a formulation change quietly moved the safety margin
When the Canadian Explosives Research Laboratory characterised a commercial ammonium nitrate emulsion, the base formulation measured 0.422 W/m·K. Adding 6% glass microballoons (a change made to sensitise the emulsion, not to alter its thermal behaviour) brought that down to 0.309 W/m·K. That is a 27% reduction in the material’s ability to shed decomposition heat, introduced by a decision taken for an entirely unrelated reason. Aluminium loading up to 10%, by contrast, left conductivity essentially unchanged.
Neither outcome is predictable from a handbook value for ammonium nitrate, and the direction of the effect is not intuitive. Both were measured in seconds, from a few millilitres of emulsion, on the material as formulated. Published work confirms thermal conductivity exerts a large influence on predicted time-to-ignition under quasi-adiabatic conditions, which is precisely why it is measured rather than assumed.
See It in Action
Request a demonstration to see how the C-Therm Trident delivers fast, low-energy, repeatable thermal conductivity measurements on explosives, propellants and energetic powders, from as little as 1.25 mL.
Customer Success Stories
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NASA
We purchased the C-Therm Thermal Conductivity Analyzer after seeing a demonstration of how fast and easy it is to operate. The instrument provides unequivocal results and provides the flexibility to test powders and liquids. In terms of our satisfaction with the purchase, I’d give it a 10 out of 10 – extremely satisfied.
Dr. Enrique JacksonSector: Aerospace
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Centre for Industrial Rheology
…The MTPS method available on C-Therm’s Trident System is a perfect fit for us, providing a simple, highly accurate, practical, and versatile route for measuring thermal conductivity of semi-solids, powders, and fluids. The MTPS is a welcome addition to our capabilities, helping to complete our service offering, and has been a boon to the growth of our business.
Neil CunninghamFounder & CEO
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Northeastern University, Boston
… I received a rare chance to see how their instrument works on my sample and hits the performance expectations I have. The sales team is professional and knowledgeable as they understand what their customer truly needs and the weight of purchase decision the customer faces on such instrument.
Melissa ChenResearch Scientist
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TÜV SÜD
Using the Trident system for thermal conductivity testing of our process safety studies and related contract testing has provided our lab with invaluable new capabilities, with great support from the team at C-Therm.
Delphine BersetProcess Safety
Explosives & Energetic Materials Webinars and Technical Videos
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Webinar: Thermal Conductivity Testing of Explosives & Propellants
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Webinar: Material Characterization in the Development of Advanced Defense Subsystems
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Webinar: Thermal Conductivity Factors in Energetics and Process Safety Research
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Webinar Snippet: How Thermal Conductivity Helps Predict Explosion Risk in Energetic Materials
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Automated Thermal Control (ATC) for Elevated Temperature Testing
Application Resources
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Application of the Modified Transient Plane Source Technique for Early Detection of Liquid Explosives
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Study on the Effect of NTO on the Performance of HMX-Based Aluminized Cast-PBX
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Thermal Conductivity Testing of Minimal Volumes of Energetic Powders
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Effect of Inert Plasticizers on Mechanical, Thermal, and Sensitivity Properties of Polyurethane-Based Plastic Bonded Explosives
Thermal Conductivity Instrument & Sensors for Energetic Materials Testing
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Trident Thermal Conductivity Instrument
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MTPS Thermal Conductivity Sensor
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The MTPS sensor equipped with the powder cell, ideal for testing the thermal conductivity of energetic powders, emulsions, or liquids.
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MTPS sensor with a liquid sample
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Automated Thermal Control (ATC) – simplifies elevated-temperature thermal conductivity testing
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Understanding the thermal conductivity of an explosive material can help predict the conditions that will cause ignition, which helps prevent premature explosions
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Propellants are a necessity for the aerospace industry, needing greater performance for longer distances and heavier loads. Understanding the thermal conductivity of these materials allows for greater performance insight.
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TPS thermal conductivity sensors
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TLS thermal conductivity sensor
Technical Specifications
C-Therm Trident – Comparison of Methods
| Specification | MTPS (emulsions, powders, pastes, liquids, cured solids) |
TPS (granules, composites, anisotropic solids) |
TLS (flowable, granular and bulk media) |
|---|---|---|---|
| Thermal Conductivity Range | 0.01–500 W/m·K | 0.005–2000 W/m·K | 0.1–6 W/m·K |
| Volumetric Heat Capacity | Up to 5 MJ/m³·K* | Up to 5 MJ/m³·K | – |
| Temperature Range | –50 to 200°C | –200 to 600°C | –55 to 300°C |
| Precision | Better than 1% | Better than 2% | Better than 3% |
| Accuracy | Better than 5% | Better than 3% | ± (3% + 0.02) W/m·K at 20 °C |
| Test Time | 0.8–3 s | 10–180 s | Less than 4 min |
| Sensor Dimensions | Ø18 mm | Ø6, Ø13, Ø30 mm sensors | 150 mm length |
| International Standards | ASTM D7984 | ISO 22007-2 ASTM E3088 |
ASTM D5334 |
*Calculated parameter
Frequently Asked Questions
The C-Therm Trident is a transient thermal conductivity platform used by energetics laboratories to characterise explosives, propellants, pyrotechnics and reactive powders. Its Modified Transient Plane Source (MTPS) sensor, defined in ASTM D7984 and available exclusively on C-Therm instruments, measures thermal conductivity, thermal effusivity and volumetric heat capacity from as little as 1.25 mL of sample in 0.8 to 3 seconds. The sensor is single-sided and requires no machining, no thermal grease and no steady-state hold, which is why it is used where sample quantity, contact time and handling exposure are the binding constraints.
To discuss your specific sample, contact us or book a demo with one of our experts.
There is no thermal conductivity standard written specifically for energetics. The applicable standard is selected by the physical state of the specimen. ASTM D7984 covers the Modified Transient Plane Source method and is the appropriate route for emulsions, powders, pastes, liquids and cured solids. ISO 22007-2 and ASTM E3088-25 cover the Transient Plane Source method for solid, granular and composite specimens. ASTM D5334 covers the transient line source needle probe for bulk flowable media. ASTM C177 and ISO 8302 (guarded hot plate) and ASTM E1461 (laser flash) exist but impose specimen-geometry and steady-state requirements that are usually impractical for reactive materials.
Separately, the NATO STANAG series governs thermal stability and compatibility testing of explosives, STANAG 4515 (DTA, DSC, HFC, TGA), STANAG 4147 (chemical compatibility), STANAG 4582 (nitrocellulose propellant stability by heat flow calorimetry). These are calorimetric standards. They do not cover thermal conductivity, which is why a complete thermal dossier needs both a calorimetric technique and a transport-property measurement.
To discuss methods and standards applicable to your specimens, contact us.
1.25 mL is the stated minimum for liquids and powders using the MTPS Liquids & Powders Cell on the Trident. For a typical energetic that is on the order of one to two grams. Cured or pressed solids require only a flat face large enough to seat the 18 mm sensor. By comparison, the United Nations H.1 US SADT test requires between 400 g and 200 kg of material and runs for seven days. The small-volume transport measurement is what makes a modelled SADT determination viable for developmental formulations that do not exist in kilogram quantities.
Guarded hot plate (ASTM C177 / ISO 8302) is the primary absolute method for thermal conductivity and is the correct reference technique for inert, machinable, low-conductivity solids. It is rarely practical for energetics. It requires a large specimen machined to parallel faces, holds that specimen at elevated temperature for hours while steady state is established, and cannot accept an emulsion, paste or loose powder without a containment fixture that changes what is being measured. For reactive materials the governing criteria are sample quantity, contact time and handling exposure, and on all three a transient method is preferable. MTPS under ASTM D7984 returns a calibrated result from 1.25 mL in under three seconds.
To discuss your specific sample and the most suitable method, contact us or book a demo with one of our experts.
Thermal conductivity determines the rate at which decomposition heat generated inside a mass of material reaches its boundary. In the Frank-Kamenetskii treatment, which applies to conduction-limited solid and viscous systems, the criticality parameter δ scales as a²/λ — so the critical half-dimension scales as √λ and the critical mass as λ^1.5. Published work shows thermal conductivity exerts a large influence on predicted time-to-ignition under quasi-adiabatic conditions. A modelled SADT built on kinetics from DSC or ARC but on an assumed thermal conductivity carries that assumption straight into the storage limit it produces.
A slow or fast cook-off simulation needs decomposition kinetics (activation energy, pre-exponential factor, heat of reaction) plus three transport and storage properties: thermal conductivity, volumetric heat capacity and density. Kinetics come from DSC, ARC or heat flow calorimetry; thermal conductivity and volumetric heat capacity are measured directly by MTPS under ASTM D7984. Because the properties must describe the filled, cured formulation: binder, plasticiser, aluminium, void fraction and all, handbook values for the neat energetic are not a substitute. Test procedures such as STANAG 4382 (slow heating), STANAG 4240 (fast heating) and the MIL-STD-2105 hazard-assessment series define the experiments the model is validated against.
Yes. The MTPS Liquids & Powders Cell holds the emulsion in a fixed geometry against the single-sided sensor, so the material is measured as formulated, no dilution, no drying, no machining. The Canadian Explosives Research Laboratory used this configuration to measure a commercial ANE, recording 0.422 W/m·K for the base emulsion and showing that 6% glass-microballoon loading reduced conductivity to 0.309 W/m·K while aluminium loading up to 10% left it essentially unchanged. A weighted cap ensures complete sensor coverage and repeatable contact.
Yes. The Trident accepts three sensor types on one platform. MTPS handles emulsions, powders, pastes, liquids and cured solids through a single-sided contact measurement. TPS handles granules, composites and anisotropic solids in a double-sided configuration. TLS handles bulk flowable and granular media. For an energetics laboratory whose sample inventory spans a cast charge, a pressed pellet, a loose oxidiser powder and a pumped emulsion, this removes the need to correlate results across separate instruments with different measurement bases.
Have questions about using the Trident for your specific materials? Contact us or book a demo with one of our experts.
MTPS applies a short, low-power heat pulse and reads the transient response over 0.8 to 3 seconds. The temperature excursion at the sensor interface is small and brief by design, and the total energy delivered to the specimen is orders of magnitude below that of a steady-state method holding the same specimen at an elevated set point for hours, or a flash method depositing a high-intensity pulse onto a coated face. Short contact time also shortens the operator’s handling time, and C-Therm can advise on configuration options that mitigate unnecessary electrostatic exposure when characterising sensitive formulations.
Because the value that matters belongs to the formulation, not to the neat compound. Binder chemistry, plasticiser content, oxidiser loading, metal fuel addition, particle size distribution, void fraction, packing density and moisture all shift effective thermal conductivity, frequently by more than the model’s tolerance for error. The CERL emulsion data illustrate the point directly: a 6% glass-microballoon addition made for sensitisation reasons reduced the emulsion’s conductivity by 27%, a change no ammonium nitrate handbook value would predict. Where δ scales as 1/λ, that error propagates into every critical-dimension and storage-limit calculation downstream.
For hazard and cook-off modelling, yes. The relevant temperature range runs from cold-storage conditions up to the onset of decomposition, and thermal conductivity is not constant across it, particularly for filled, porous or phase-changing systems. The Trident’s Automated Thermal Control stage covers ambient to 300 °C and the thermal chamber covers −73 °C to 200 °C, so a temperature series can be generated on the same specimen and fed to the model as a function rather than a single point.
You may contact us or book a demo with one of our experts to discuss the details.
Thermal conductivity (λ, W/m·K) describes how readily heat is transported through the material at steady state, and it sets the conduction term in criticality and SADT calculations. Thermal diffusivity (α, mm²/s) describes how quickly a temperature change propagates and governs transient heating profiles, such as the thermal gradient through a charge during slow cook-off. Thermal effusivity (e, W·s^½/m²·K) describes how readily the material exchanges heat across an interface with its surroundings, and it is the more diagnostic parameter for hot-spot and interfacial behaviour — the property that distinguished the Licowax-filled nano-β-HMX in the desensitisation study. The MTPS sensor measures conductivity and effusivity directly and derives diffusivity and volumetric heat capacity.