Making Sense of Thermal Analysis of Composites
Introduction to Thermal Analysis
Thermal analysis covers a group of techniques allowing properties of a sample to be investigated as a function of temperature and/or time. The applied temperature system consists of a sequence of segments where the sample is heated or cooled at a constant rate or held at a constant temperature. In many experiments the atmosphere also plays an important role, the most common atmospheric conditions include inert and oxidizing gases.
Glass Transition Temperature
Franklin Fibre reinforced composites are excellent thermal insulators. One of the most important factors when choosing a Lamitex ® composite is to determine whether or not the glass transition temperature will be affected by the heat applied during use. Often confused with the melting point, the glass transition temperature is actually a range of temperatures where softening occurs. Glass transition temperature (often referred to as ‘T sub g’) is the point when the glass or base substrate of the composite will soften, affecting the overall flexural modulus of the composite among other properties
ASTM C168-15 defines thermal conductivity as; "time rate of steady state heat flow through a unit area of a material or construction induced by a unit temperature difference between the body surfaces". Essentially, the amount of heat that is able to pass through the specimen to the ‘thermometer’ (or other associated thermal probe) on the other side during a specific amount of time.
Thermogravimetric analysis (TGA)
In thermogravimetry, the mass of a sample is measured while it is subjected to a temperature sequence. The measurement is performed in a controlled atmosphere, usually in nitrogen (inert condition) or in air (or oxidizing condition). The mass is recorded with a highly sensitive electronic balance. Interfering buoyancy and drag force effects are compensated by blank curve subtraction.
Evolved gases from the sample can be analyzed (EGA, Evolved Gas Analysis) in a coupled mass spectrometer.
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