Meaning
Thermal analysis protocol provides the standardized methodology for measuring glass transition temperatures in semicrystalline polymers under controlled heating ramps. ISO 11357-2 governs differential scanning calorimetry testing to isolate the specific heat capacity change associated with amorphous chain mobility. Practitioners apply this procedure to pelletized thermoplastics before processing to verify incoming resin grades against compounding specifications.
Thermal Window
Differential scanning calorimetry equipment records heat flow differentials between a sample crucible and an inert reference pan throughout precise temperature sweeps. ISO 11357-2 mandates specific purge gas flow rates and cooling rates to eliminate baseline drift during the initial thermal sweep. Technicians must execute a preliminary heating run to erase thermal history imparted by prior pellet extrusion or pelletization.
Subsequent cooling schedules establish uniform morphology across competing resin batches before the final quantitative scan occurs.
Property Drift
Baseline shifts on the thermogram indicate the onset and midpoint of amorphous phase softening within the polymer matrix. ISO 11357-2 evaluation methods pinpoint the inflection coordinates that separate glassy behavior from rubbery compliance. Variations in moisture content or residual monomer levels shift these transition bounds upward or downward relative to virgin resin baselines.
Moulders monitor these thermal shifts because unrecognized shifts alter volumetric shrinkage inside the mold cavity during high-pressure injection phases.
Regrind Economy
Recycling scrap streams requires rigorous adherence to thermal baselines because repeated thermal cycles degrade polymer chain length and alter heat absorption profiles. ISO 11357-2 data exposes the broadening of transition intervals that signals thermal degradation in recycled polyolefins and engineering thermoplastics. Blending regrind with virgin pellets compresses the processing window and demands precise thermal verification to prevent part warping and premature mechanical failure.
Laboratory instrumentation detects subtle variations between virgin stocks and degraded regrind fractions long before molded components show visible surface defects.
