Meaning
Analytical curves mapping the heat flow or dimensional changes of a polymer over a range of temperatures identify its physical phase transitions. Characterizing the thermal transition profile of a resin allows molders to determine its glass transition temperature, crystallization temperature, crystalline melting point, and onset of thermal degradation.
Analytical Technique
Differential scanning calorimetry represents the primary method used to generate these transition maps. By heating a small sample of resin at a controlled rate alongside an empty reference pan, the instrument measures the differences in heat flow associated with endothermic and exothermic events. These events appear as peaks and steps on the resulting thermogram, showing where the polymer transitions from a rigid solid to a flowable liquid.
Molders use this data to confirm the thermal history and crystalline structure of incoming resin batches.
Processing Relevance
Understanding these transition temperatures is critical for optimizing both the extrusion and molding cycles. For example, the crystallization temperature determines the point at which a semi-crystalline polymer can be ejected from the mold without deforming. If the mold temperature is set too high, the cooling phase must be extended to allow the polymer to solidify, reducing overall production efficiency.
Quality Control
Comparing the thermal transition profile of a production batch against a reference baseline helps detect contamination and molecular weight variations.
