Scope
- DSC enables a range of characteristics to be measured to benchmark materials.
- These include quality control, material and process development activities, failure investigations, and material identification
- DSC Testing Explores the Following Material Properties:
- Glass transition temperature (Tg): The material Tg is the temperature where the material transitions from a rigid glassy state to a rubbery state. This may limit the temperature performance of the material.
- Melt point temperature: In conjunction with infrared analysis, melting point can be used to differentiate different types of the same generic polymer type (copolymer, homopolymer etc.).
- Purity: The presence of multiple melt points and/or wavy heat flow traces can be used to detect the presence of contamination in recycled materials e.g. PE in PP.
- Crystallinity level: Crystallinity is determined from the melting enthalpy compared against the theoretical enthalpy for a 100% crystalline reference sample. To fully understand material and product performance, the amount of crystallinity is very important as it influences the level of shrinkage, material properties and chemical resistance. It is controlled by the processing parameters (cooling from the melt).
- Cure state: For cross-linked materials, the presence of any residual exothermic reaction may indicate that the material is not fully cured.
- Specific heat capacity (cp): This is the quantity of heat necessary to raise the temperature of unit mass of material by 1 K at constant pressure.
- Isothermal tests can also be carried out to determine:
- Oxidation Induction Time or Temperature (OIT) - This test measures the time or temperature for oxidative decomposition. It is widely used for polyethylene pipes but can also be used for material development programs and as part of failure investigations to assess the residual life of materials taken from service.
- Reaction studies - Evaluation of the reaction times to optimize processing conditions.
Test Procedure
- A small sample of the material (typically <10mg) is heated and compared against an inert reference material.
- Any endothermic or exothermic reactions are then recorded to get a detailed picture of polymer performance.
Specimen Size
- A minimum of 20mg of material is required for testing.
This test description is generic, and standards should be obtained from relevant authorities.