Thermal Analysis Flashcards
(16 cards)
What is an endothermic process?
A process that involves the taking in of heat.
Endothermic processes absorb heat from their surroundings.
What does the Gibbs free energy equation relate to in thermal analysis?
It relates changes in free energy, enthalpy, and entropy during a process.
The equation is essential for understanding thermodynamic processes.
What is Differential Scanning Calorimetry (DSC)?
A technique that measures heat flow associated with phase transitions in materials.
DSC is used to assess thermal properties of materials.
What are the two types of thermal events measured by DSC?
- Endothermic
- Exothermic
Endothermic events absorb heat, while exothermic events release heat.
What is the purpose of using a purge gas in DSC?
To provide a dry, inert atmosphere, aid heat flow, and carry away gases.
Common purge gases include nitrogen.
What is the typical scan rate for DSC?
10°C per minute.
This rate is standard for many thermal analysis applications.
What should be checked before using a sample in DSC to avoid decomposition?
Check with TGA first and stay clear of decomposition temperature.
TGA provides thermal stability information.
What is the significance of the glass transition temperature (Tg) in polymers?
Each polymer has an individual glass transition temperature.
Tg indicates the temperature range where the polymer transitions from a brittle, glassy state to a ductile, rubbery state.
How can purity be assessed using DSC?
Based on melting peak temperature depression by impurities.
A higher purity results in a sharper melting peak.
What is the formula for calculating % crystallinity?
% crystallinity = 100 - % amorphous.
This calculation helps determine the crystalline content in a sample.
What are the applications of DSC?
- Identification
- Melting point
- Enthalpy
- Glass transition temperature
- Polymorphic forms
- Re-crystallisation
- Phase transformation
- Purity
- Miscibility
These applications are crucial for characterizing materials in pharmaceuticals.
True or False: DSC can be used to measure only melting points.
False.
DSC measures various thermal events, not just melting points.
Fill in the blank: The energy required to maintain _______ is measured during DSC.
ΔT = 0.
This measurement is crucial for calorimetric assessments.
What materials are typically used for sample pans in DSC?
Aluminium.
Aluminium pans are commonly used due to their thermal conductivity.
What is the significance of melting temperature (Tm) in DSC?
It indicates the temperature at which a solid becomes a liquid.
Tm is a critical parameter for assessing material purity and stability.
What types of polymer blends can be analyzed using DSC?
- Miscible polymer blends
- Immiscible polymer blends
These blends have different thermal properties and behaviors.
