Thermal Hysteresis

Moulding Divergence

Injection cycle stability depends on how accurately the machine controls temperature relative to these non-identical phase change points. Process engineers observe thermal hysteresis when the transition from molten to solid occurs at a lower temperature than the initial melt point. Frequent measurement of these distinct peak temperatures ensures the holding pressure maintains density control before the polymer completes its crystalline shift.

Large gaps between these points demand longer cooling times to prevent internal stress or dimensional warping in the finished part.

Material Economics

Regrind incorporation shifts the transition dynamics as molecular weight distributions broaden across multiple heat histories. Virgin pellets demonstrate a narrower window because the polymer chains maintain higher uniformity and consistent branching. Moulders often calculate the shift in transition energy to adjust cycle times when blending recycled content into the barrel.

This adjustment prevents premature freezing or inconsistent viscosity during the filling phase of the cycle.

Control Precision

Sensor placement within the mould cavity determines if the controller catches the actual transition or merely detects heater output. Equipment accuracy hinges on the capacity to track the lag between applied thermal energy and the resulting change in resin state. Variations in wall thickness create localized zones where the material exits the melt phase at different times than the bulk stream.

Advanced process control links the cooling phase to the specific temperature points identified during initial material characterization.