Thermal Analysis 

Thermal analysis provides very useful and relevant information for a number of various materials.  By utilizing various techniques, H&M can determine the melting point, glass transition temperature, weight loss, specific heat and other material properties.  This is achieved by employing 2 different but complimentary characterization techniques, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).

Thermal Gravimetric Analysis

TGA can measure the changes in a samples weight in a controlled environment as a function of either temperature or time.  The weight loss occurs due to the changing of chemical or physical properties and can be detected down to fractions of a micro-gram.  Based on the type of sample and information that’s required, the test can be performed by fixing the temperature over a range of time or by ramping the temperature over a fixed time period.  Both of these methodologies provide information of thermal stability.

Differential Scanning Calorimetry

DSC consists of exposing a small quantity of a sample, typically 0.5 to 100 mg, to a controlled heating program with a known reference material in the chamber in order to measure the temperature difference between them.    If the sample undergoes a thermal event that absorbs more heat than the reference, this corresponds to a decrease in the heat flow on the DSC and is called an endothermic process.  An example of this behavior is once a material reaches its melting point.  The opposite reaction is called an exothermic event and this occurs when the DSC displays an increase in heat flow compared to the reference.  An example of this behavior is a crystallization point for a specified material.  Determining the exact point of these transitions is important in evaluating the presence of a polymorph in pharmaceutical samples or identifying an unknown material or phase.  Standard steady state heating cycles, multiple heating or cooling ramps, and isothermal holds can be utilized to study different thermal events.

Main Applications of Thermal Analysis

TGA

  • Thermal stability of a solid or liquid
  • Decomposition kinetics of volatile materials
  • Absorbed moisture content
  • Screening of additives

DSC

  • Characterization of phase transitions in glasses and other materials
  • Determining the heat capacity
  • Oxidative stability
  • ID of unknown impurities in materials
  • Characterizing polymorphic materials

 

Pros

  • Small sample size
  • Very precise temperature control
  • Analysis of solids and liquids with minimal sample preparation
  • Highly accurate measurement of phase transitions and heat capacities (DSC)
  • Sensitive measurement of subtle or weak phase transitions (DSC)
  • Qualitative or quantitative analysis (TGA)
  • Detection of multiple mass loss thermal events from physical and chemical changes of materials (TGA)

Cons

  • Destructive test
  • Accurate data cannot be obtained when a decomposition or reaction event occurs within the same temperature region as the phase transition like melting point (DSC)
  • Mass of sample has to remain constant in the pan for accurate measurement; that means no loss of sample to evaporation or sublimation during the test (DSC)

Detailed Analysis

Decomposition of Pharmaceuticals

Thermal analysis is a common characterization technique used in the manufacturing and testing of pharmaceutical drugs.  TGA is a common methodology to examine the excipients that are used pharma manufacturing.  It is vital to know how the active ingredients in the drug will thermally behave with the numerous excipients when combined. TGA can provide data based on the decomposition or decomposition’s at various temperatures.  Pharma products can be manufactured using hot melt extrusion techniques which all the components are exposed to elevated temperatures.  It is require information to ensure that all the components have excellent thermal stability.

Pharmaceutical Drugs Pharma Products

Application based Polymer Testing

There are numerous polymers that are used in everyday life covering a wide berth of applications.  Polymers themselves are long chains of molecules and the they behave differently based on the linkage of the molecules and the conditions that they are formed, primarily pressure and temperatures.  DSC provides a large amount of data on how a polymer can perform based on its thermal data.  Polymers that are exposed to increased temperatures require high melting points.  When a known or unknown polymer is tested using DSC the following information can be revealed:

  • Glass transition temperature
  • Enthalpy
  • Crystallization point
  • Melting point
  • Heat capacity

Atomic view of polymer formation

 

Thermal Analysis Equipment

Technical Specifications of Equipment

TGA

  • Signal detected: Mass and temperature change
  • Sample size range: 10 mg to 1 g
  • Temperature range: Ambient to 1000°C
  • Controlled heating rate: 0.01 to 100°C/minute
  • Weighing precision: +/- 0.01%

DSC

  • Temperature range: -40°C  to 400°C
  • Controlled heating rate: 0.01 to 200°C/minute
  • Temperature accuracy: +/- 0.1°C
  • Temperature precision: +/- 0.05°C
  • Sample size Range: 0.5 mg to 100 mg

Key Markets Served

  • Pharmaceuticals
  • Semiconductors
  • Coatings and Adhesives
  • Glass Manufacturing
  • Polymers & Plastics
  • Aerospace
  • Solar and Lighting
  • Defense
  • Data Storage
  • Raw Chemicals
  • Personal Care
  • Packaging
  • Life Sciences
  • Law and Litigation

 Application Notes

Decomposition Analysis of Calcium Oxalate Using TGA