Thermal Conductivity

Heat Transfer

Injection moulding cycles depend upon the rapid dissipation of energy from the molten plastic into the cooling channels of the steel tool. High values allow for shorter dwell times because the plastic loses internal heat to the mould surfaces at a higher rate. Low values act as an insulator, which retains heat in thick sections and causes differential cooling during solidification.

Excessive heat retention leads to internal voids, sink marks, and residual stresses that deform the finished part after ejection.

Material Specification

Datasheet values represent the bulk property of a virgin resin tested under controlled laboratory conditions. Processors find that actual moulding performance varies from these static values due to the addition of fillers, pigments, or glass fibers. Recycled resins exhibit lower consistency because contaminant particles create thermal barriers that impede uniform conduction across the melt.

Moulders adjust holding pressures and cooling durations to compensate for the drift in conduction rates that happens when the resin source changes.

Processing Impact

Tool designers choose alloy grades based on the need to move heat away from the part interface. High conductivity steels prevent local hot spots on the cavity surface that degrade thin sections of the plastic part. Surface finish remains uniform only when the heat flux stays consistent across the entire mould geometry throughout the injection phase.

The cooling rate determines the crystalline structure of semi-crystalline polymers, so fluctuations in conduction directly alter the final mechanical strength of the moulded product.