LS_CHT_BIA_L34_Thermal Analysis Part 1

Basic Instrumental Analysis

• Module Code: LS5006FPR/5012FP

• Lesson 34: Thermal Analysis - Differential Scanning Calorimeter Part 1

Learning Objectives

• Understand the purpose & working principle of DSC

• Describe the basic components and their functions in DSC

• Explain the importance of sample preparation for DSC

• Understand the applications of DSC

Introduction to Thermal Analysis

• Thermoanalytical methods: TGA and DSC

• TGA measures weight changes; DSC measures heats and temperature of transitions/reactions.

Introduction to DSC

• DSC measures temperature and heat flow related to thermal transitions.

• It records heat absorbed/released by samples during heating, cooling, or held at constant temperature.

• Sample and reference are maintained at nearly the same temperature.

Components of DSC

• Furnace: Main assembly where sample & reference are heated.

• Sample holder: Contains sample and reference material.

• Cooling system: Cools sample for desired temperature program.

• Computer: Interface for monitoring temperature and regulating heat flow.

• Work with small aluminum pans in nitrogen atmosphere to eliminate air oxidation.

Sample Preparation

• Pan type: Small sample pieces in aluminum pans (up to 600ºC); other materials (gold, copper, platinum, graphite) for higher temperatures.

• Samples must be thin to minimize thermal gradients; should be cut, not crushed, to ensure uniform contact with the pan.

• Advantages of crimped pans: Improve contact, reduce thermal gradients, minimize spillage.

• Sample Mass: Appropriate range is 1 mg to 10 mg.

• Precautions: Avoid direct contact with pans/lids; use gloves and goggles to prevent contamination.

Principle of DSC - Detection of Phase Transitions

• Heat flow varies during phase transitions (endothermic vs exothermic).

• Endothermic processes require more heat (e.g., melting); exothermic processes release heat (e.g., crystallization).

• Measured temperature differences indicate heat absorption or release during transitions.

Applications of DSC

• Determining: Glass transition temperature (Tg), Melting temperature (Tm), Heat of fusion, Crystallization temperature (Tc), Oxidative/thermal stability, Curing kinetics.

Summary

• DSC measures temperature and heat flows associated with thermal transitions.

• Provides quantitative and qualitative data on endothermic and exothermic processes during physical transitions.