Thermal Analysis - units.it

Thermal Analysis Different Techniques Thermometric Titration (TT) Heat of mixing Thermal Mechanical Analysis (TMA) Thermal Expansion Coefficient Dynamic Mechanical Analysis (DMA)

Viscoelastic Properties Differential Scanning Calorimetric (DSC) Heat flow during Transitions Thermal Gravimetric Analysis (TGA) Weight Loss due to decomposition Derivative Thermogravimetric Analysis (DTG) Differential Thermal Analysis (DTA)

Heat of Transitions Temperature Programmed Desorption (TPD) Temperature at which gas is desorbed from (catalyst) surface Emission gas Thermoanalysis (EGT) Basic Principle Sample is heated at a constant heating rate Samples Property Measured Wt TGA Size TMA

Heat Flow DSC Temp DTA Gas evolved TPD TGA Constant Heating Rate Initial Temp Final Temp Heating Rate (C/min) Data Weight vs Time

Weight vs Temp. Differential This Data (DTG) DSC DSC Constant Heating Rate Initial Temp Final Temp Heating Rate (C/min) Data Heat flow to sample minus Heat flow to reference vs

Time (Temp.) Measures heat of crystallization Polymer without weight change in this temperature range DTA Sample and Reference Placed in Heater Constant Heating Rate Initial Temp Final Temp Heating Rate (C/min) Data Temp of Sample vs Time (or Temp) Temp of Reference vs Time (or Temp)

Reference should be inert, e.g. nothing but latent heat Measures Heat of crystallization Glass Transition Temperature DTA + DTG TMA Constant Heating Rate Initial Temp Final Temp Heating Rate (C/min) Data Size of Sample vs Time (or Temp.)

Measures Thermal Expansion Coefficient Volume change on crystalization or crystal transformations Sintering Glass Transitions in Polymers TMA Polymer with glass transition DMA Constant Heating Rate Initial Temp Final Temp

Heating Rate (C/min) Data Force vs Time (or Temp.) Force delay vs Time (or Temp.) Viscoelastic Properties Storage and Loss Modulus Measures Glass Transition Viscoelastic Properties Polymer with Glass Transition Typical Features of a DSC Trace

Exothermic upwards Endothermic downwards ^exo MELTING CRYSTALLISATION GLASS TRANSITION DESOLVATION 20 mW H2 O DECOMPOSITION

Y-axis heat flow X-axis temperature (and time) 40 60 80 100 120 140 160 180 200 220 240 260 280 300 o temperature [ C] Modulated Temperature DSC (MTDSC)

This technique uses composite heating profile: determines heat capacity and separates heat flow into the reversible and non-reversible components Benefits Increased sensitivity for detecting weak transitions especially glass transition Separation of complex events into their:

heat capacity (reversible) e.g. glass transition, melting and kinetic components (non-reversible) e.g. evaporation, crystallisation, decomposition Variants of MTDSC Sinusoidal modulation (easy, only one frequency only) TA Instruments

Step scan modulation (easy, precise) PerkinElmer TOPEM modulation (stochastic modulation, complex calculations, but multiple frequency data) Mettler Toledo Example of a MTDSC Curve Polyethylene terephthalate (PET)

Source: Craig DQM and Reading M Thermal analysis of pharmaceuticals