Meaning
Thermal analysis instruments measure heat flow associated with phase transitions under a controlled, elevated gas pressure. By suppressing volatile losses and shifting chemical equilibria, high pressure dsc enables the characterization of polymers at pressures up to several hundred bars. This method provides critical data on crystallization temperatures and oxidation stability that standard atmospheric testing cannot replicate.
Pressure Effect
Elevated pressure alters the free volume of the polymer chains, which restricts molecular mobility and increases the glass transition temperature. In processes like injection moulding, where cavity pressures are high, the crystallisation temperature shifts upward during cooling. Utilizing high pressure dsc helps the moulder predict the exact point of solidification within the mould cavity.
Thermal Transition
Oxidative induction time measurements benefit from this pressurized environment because the higher concentration of oxygen accelerates the degradation reaction without requiring excessively high temperatures. This acceleration yields precise stability ratings for virgin resins containing antioxidant packages. Regrind materials can be compared against these baselines to evaluate how many heat histories the material has undergone before losing its thermal stability.
Operational Limit
Sealing the sample chamber requires thick-walled metal cells that can withstand both extreme temperatures and high gas pressures. If the seal fails during a test, sudden decompression occurs, which ruins the sensor and invalidates the thermal curve.
