Differential Scanning Calorimetry (DSC) according to ISO 11357-1

glass transition
Testing lab
Plastic characterization
Testing standard

ISO 11357-1, ASTM D3418, ASTM E1356

DSC

DSC is a versatile and essential method for characterizing the thermal behavior of plastics. It provides valuable insights for quality control, material identification, processing conditions, and performance prediction of polymer products.

Differential scanning calorimetry, or DSC, is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature. Both the sample and reference are maintained at nearly the same temperature throughout the experiment. In general, the temperature programme for a DSC analysis is designed such that the sample holder temperature increases linearly as a function of time.

If a material is heated a chemical of physical reaction can occur which is linked to absorption or release of heat. DSC equipment is able to measure this energy changes.

Test principle

ISO 11357-1: Plastics – Differential Scanning Calorimetry (DSC) – Part 1: General Principles

ISO 11357-1 describes the general principles of Differential Scanning Calorimetry (DSC), a thermal analysis technique used to measure how a plastic material responds to changes in temperature. DSC provides critical information about thermal transitions such as glass transition temperature (Tg), melting temperature (Tm), crystallization, and oxidative stability, among others.

Test Procedure

  • Sample Preparation:
    • A small specimen (typically 5–20 mg) of the plastic material is placed in a sealed or open DSC pan, depending on the nature of the test and material.
  • Instrument Setup:
    • The DSC instrument has two pans: one with the sample and one empty (reference).
    • Both pans are subjected to a controlled temperature program (heating, cooling, or isothermal).
  • Measurement Process:
    • As the temperature changes, the instrument measures the difference in heat flow between the sample and the reference.
    • When the sample undergoes a thermal event (e.g. melting, crystallization, glass transition), its heat flow changes, and this is recorded as a DSC curve (thermogram).
  • Test Conditions:
    • Heating/cooling rates, atmosphere (nitrogen, air, etc.), and temperature range are chosen based on the material and purpose of the test.
    • Standard heating rates are often 10°C/min but can vary depending on the application.
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Key Thermal Properties Measured

  • Glass Transition Temperature (Tg): Indicates the transition from a rigid to a more rubbery state.
  • Melting Temperature (Tm): The point at which the crystalline regions of a polymer melt.
  • Crystallization Temperature (Tc): The temperature at which the material crystallizes upon cooling.
  • Heat of Fusion (ΔHf): Energy required to melt the material, linked to crystallinity.
  • Oxidative Induction Time/Temperature (OIT): Assesses thermal-oxidative stability (covered in ISO 11357-6).

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