Introduction to Thermal Analysis
Thermal analysis encompasses a family of techniques that measure the physical and chemical properties of materials as a function of temperature. Among these, Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC) are the most widely used for characterising polymers, pharmaceuticals, metals, ceramics, and composites across the plastics, materials science, and thermal engineering industries.
Both techniques monitor thermal events—melting, crystallisation, glass transitions, curing reactions, and decomposition—that reveal fundamental information about material structure, composition, and processing history.
What Is Differential Thermal Analysis (DTA)?
DTA measures the temperature difference (ΔT) between a sample and an inert reference material as both are heated or cooled at a controlled rate. When the sample undergoes a thermal event (endothermic or exothermic), its temperature deviates from the reference, producing a peak or trough in the ΔT vs. temperature plot.
DTA is a qualitative to semi-quantitative technique. It identifies the temperatures at which thermal events occur but does not directly measure the heat flow associated with those events.
Typical DTA Applications
- Phase diagram determination in ceramics and metallurgy
- Identification of mineral phases
- Qualitative assessment of polymer thermal transitions
- High-temperature materials characterisation (up to 2400°C for specialised instruments)
What Is Differential Scanning Calorimetry (DSC)?
DSC measures the heat flow (mW or mW/g) required to maintain a sample and reference at the same temperature (or the temperature difference under constant heat flow) as a function of temperature. It is a quantitative technique that directly measures enthalpy changes associated with thermal events.
Two Types of DSC
Heat Flux DSC: Measures the temperature difference between the sample and reference on the same furnace block, converting it to heat flow via a calibrated constant.
Power Compensation DSC: Uses separate furnaces for sample and reference, measuring the power difference required to keep them at the same temperature. Offers superior sensitivity and resolution.
Key Thermal Events Measured by DSC
Event | DSC Signal | Information Obtained |
Glass transition (Tg) | Step change in heat flow | Amorphous content, plasticization |
Melting (Tm) | Endothermic peak | Crystallinity, purity |
Crystallisation (Tc) | Exothermic peak | Crystallization kinetics |
Curing (thermosets) | Exothermic peak | Degree of cure, reaction enthalpy |
Oxidation induction time (OIT) | Exothermic onset | Antioxidant efficacy |
Decomposition | Endothermic/exothermic | Thermal stability |
DSC in Polymer Characterisation
DSC is the primary tool for polymer thermal characterisation:
- Percent crystallinity: Calculated from the measured melting enthalpy divided by the theoretical enthalpy for 100% crystalline polymer.
- Glass transition temperature (Tg): Critical for selecting polymers for service temperature ranges. Below Tg, amorphous polymers become glassy and brittle.
- Oxidation Induction Time (OIT): Measures antioxidant stability of polyolefins (ASTM D3895, D6186) — critical for long-life applications such as geomembranes and pipes.
- Blend and copolymer analysis: Multiple Tg or Tm peaks indicate phase separation or multiple polymer components.
DSC vs. DTA: Choosing the Right Technique
Feature | DTA | DSC |
Output | Temperature difference | Heat flow (quantitative) |
Temperature range | Up to 2400°C | Typically −180°C to 700°C |
Sensitivity | Lower | Higher |
Quantitative data | Limited | Yes (enthalpy, Cp) |
Primary use | High-temperature materials | Polymers, pharma, organics |
Conclusion
Thermal analysis techniques like DTA and DSC are essential tools for understanding how materials respond to temperature, providing critical insights into their structure, composition, and performance. While DTA offers valuable information on the temperatures of thermal events—especially at very high temperatures—DSC delivers precise, quantitative data on heat flow, making it indispensable for polymer characterisation.
By selecting the appropriate technique and interpreting thermal transitions accurately, engineers and researchers can optimise material selection, processing conditions, and product performance. Ultimately, thermal analysis plays a key role in ensuring quality, reliability, and innovation across a wide range of industries.
Why Choose Infinita Lab for DSC and DTA Analysis?
Infinita Lab leverages a vast network of accredited labs equipped with state-of-the-art DSC and DTA instrumentation. Our thermal analysis experts design testing programs covering glass transition, melting, crystallinity, cure characterisation, and oxidation stability for all material classes.
Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you. Request a Quote
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