Meaning
Differential scanning calorimetry requires specialized containers to hold the material during heating and cooling cycles. Hermetic sample pans are metal crucibles designed to be cold-welded or crimped with a seal that prevents the exchange of gases with the environment. They ensure that the mass of the sample remains constant even when internal pressures rise due to heating or chemical reactions.
Pressure Containment
Sealing the sample allows the instrument to measure reactions that would otherwise be obscured by evaporation. High-pressure hermetic sample pans can withstand several atmospheres of internal pressure without leaking. This capability is essential for studying the curing of phenolics or other resins that release water vapor as a byproduct.
Without a sealed environment, the large endothermic peak of evaporation would mask the smaller exothermic peak of the chemical reaction.
Volatile Suppression
Loss of mass during a thermal scan introduces errors in heat flow calculations. Using hermetic sample pans prevents the escape of solvents, moisture or low-molecular-weight components. This isolation keeps the stoichiometry of the reacting system stable throughout the test.
It also protects the sensitive sensors inside the calorimeter furnace from corrosive vapors or condensables that could degrade performance over time.
Thermal Contact
Flatness and material choice impact the quality of the data collected from the furnace. Aluminum is the most common material for hermetic sample pans due to its high thermal conductivity and ease of sealing. Gold or copper alternatives are used when the sample is corrosive to aluminum or requires a different temperature range.
Ensuring a broad contact area between the pan and the sensor minimizes thermal resistance and improves the resolution of the resulting peaks.
