Meaning
Differential scanning calorimetry is a thermoanalytical technique measuring heat flow associated with material transitions as a function of temperature under a controlled program. This quantitative method establishes polymer crystallinity, glass transition temperatures, and melting points by comparing thermal changes in a specimen against an inert reference pan. Moulders use the resulting thermogram to verify incoming virgin resin integrity before compounding or processing begins.
The procedure stops applying when thermal decomposition occurs without a preceding physical state change or when samples lack homogeneity across the tested mass.
Thermal Transition
Crystallinity percentages derived from melt enthalpy curves govern final stiffness and shrinkage rates during injection moulding. Engineers set the heating rate during the compounding phase to establish baseline molecular organisation before pellets enter the machine hopper. Variations in thermal history shift the endothermic peak position, causing warp and dimensional drift in precision housings.
Moulders maintain narrow processing windows because minor shifts in polymer morphology alter shrinkage patterns across the cavity. Regrind economics require frequent testing because recycled chains exhibit degraded thermal profiles that diverge from virgin data. A material specification establishes the absolute baseline value for these transition points, whereas a part specification tolerates broader variations driven by cooling rates in the tool.
Datasheet values represent laboratory ideals that rarely match the actual performance achieved on the factory floor.
Crystallite Melting
Molecular chains absorb thermal energy during the endothermic phase, creating a specific curve that exposes nucleating agent effectiveness. Technicians detect incomplete polymerisation when the melting range broadens unexpectedly during routine quality audits. Unchecked moisture in the feed throat alters the endothermic profile, producing irregular part density and structural failure under load.
Processing parameters must compensate for variations in molecular weight distribution revealed by the initial melt peak. Cooling channels within the tool dictate how fast crystallisation occurs, directly impacting the final mechanical strength of moulded components.
Transition Velocity
Heat flux sensors track sample power differentials continuously while the furnace temperature ramps upward at a fixed linear rate. Operators calibrate baseline stability regularly to eliminate spurious signals caused by furnace asymmetry or thermocouple drift. Sample mass must remain small to prevent thermal gradients from distorting the recorded peak shape.
Instrument sensitivity determines the lowest detectable enthalpy change, allowing technicians to spot minor additive loadings in base polymers. Precise temperature control ensures that the resulting thermogram provides reliable data for mould design and tooling adjustments.
