Knowledge / Understanding the technology
Using PCM Correctly in Thermal Packaging
PCM absorbs heat when melting and releases heat when solidifying. This can stabilise temperature in thermal packaging. The melting range, quantity and preparation must match the product and transport. Two packs with the same melting point can behave differently if they are not in the same state when packed.
Practical guidance
Select the melting point and format, and define how PCM elements are prepared before packing.
PCM cooling elements in rigid shells. Item identification and the medium determine selection; colours are not a universal temperature code.
In this guide
- How PCM absorbs and releases heat
- Choose the medium first, then the appropriate format
- Why PCM +5 does not automatically hold goods at +5 °C
- The same pack temperature does not mean the same internal state
- Request these material data
- Document preparation in the packing instructions
- When the same packout can be used in summer and winter
How PCM absorbs and releases heat
PCM means Phase Change Material. In physical terms, water is one too. In thermal packaging, “PCM” often refers to specially selected media that melt and solidify at temperatures different from water.
During melting, the material absorbs heat without its temperature increasing to the same extent as after complete melting. It releases heat during solidification. Real PCMs may melt over a temperature range; melting and solidification do not necessarily occur at exactly the same temperature either. Design therefore requires data for the specific material.
Choose the medium first, then the appropriate format
The medium determines, among other things, the phase change temperature and the amount of heat absorbed. The format determines size, arrangement and handling. “PCM or foam brick?” is therefore not a valid comparison: a foam brick can be filled with PCM.
THERMOCON offers standard PCMs with melting points of −21, +5, +18 and +22 °C. In addition to rigid-shell packs, selected PCMs are available in other formats. The product overview shows the combinations offered.
For goods at +15 to +25 °C, the CRT guide explains how temperature-conditioned water and PCM differ.
Source: THERMOCON: PCM cooling elements.
Why PCM +5 does not automatically hold goods at +5 °C
A melting range near +5 °C can suit shipping at +2 to +8 °C. However, the goods’ temperature also depends on spacing, heat transfer, product quantity and initial temperatures. It therefore does not necessarily equal the PCM temperature.
First define product limits and expected ambient temperatures. Then test the medium in the complete packout. More PCM does not necessarily extend duration proportionally; it also changes the available space and heat distribution. Packs prepared too cold can also cause local excessive cooling.
The same pack temperature does not mean the same internal state
Two elements can be close to the same melting temperature even though one still contains a large amount of solid PCM and the other is predominantly liquid. The more solid material remains available to melt, the more heat this phase change can absorb. Heat release through solidification, by contrast, requires liquid PCM.
A surface measurement does not fully reveal how much of the material inside is solid or liquid. The preparation instructions therefore specify temperature, duration, stacking and permitted equipment loading. They must also describe how long the elements may subsequently be staged before packing.
For alternating warm and cold stages, the initial state is defined for the entire sequence. The designation “PCM +5” establishes neither a universal freezing temperature nor a general tempering time.
Request these material data
Ask how much heat per kilogram the medium can absorb or release within the relevant temperature range. Data sheets often call this usable enthalpy. A melting point alone does not contain this information. You also need the filling mass, dimensions, casing material and details of intended reuse.
When comparing weights, check whether a value refers to the medium or the complete pack. The casing contributes to freight weight but does not itself contain PCM.
Some materials begin to solidify only after further cooling below the actual phase change temperature. Clarify whether this behaviour, or changes after repeated use, is relevant to the offered material. Ask the supplier: “Which preparation procedure has been tested for this element, and what data are available for the intended repeated uses?”
Document preparation in the packing instructions
- Which item version is used?
- Should the medium be solid, liquid or in a defined intermediate state when packed?
- At what temperature, for how long and with what stacking arrangement are the elements prepared?
- Is an equilibration period then required, and how long may the elements be staged before packing?
- How are fully prepared elements separated from those not yet ready for use?
This preconditioning must be achieved reliably with the equipment at the dispatch site. The packing process guide provides advice on equipment loading and identification.
When the same packout can be used in summer and winter
A tested year-round packout can reduce the number of seasonal variants at the packing station. Whether the same coolant pack preparation may also be used must be explicitly demonstrated. The use of PCM alone is insufficient evidence.
Compare the effort in your own operation: how many sets of packs must be held? How long does preparation take? Do packing time, the risk of mix-ups or freight weight change? These data show whether the simpler process also offers an economic benefit.
Sources
- THERMOCON: PCM cooling elements. Available PCM melting points, sizes and formats.
Sources checked on 12 September 2026.
Compare PCM melting points and formats
Specify the product temperature range, expected ambient temperatures and your preparation facilities. Then compare suitable PCM melting points, formats and sizes.