THERMAL STABILITY OF LIGHT STABILIZERS (UV STABILIZERS): A STUDY BY TGA

TGA (Thermo-Gravimetric Analysis) is a type of thermal stability test method for chemical products that measures volatility to determine whether additives are suitable for the high processing temperature of polymers.

Two or three additive samples are placed on a table under certain conditions* and heated to measure the average temperature at which the samples lose 1, 5, 10, 20 and 50% of their weight.

*Examples of specific conditions: Heating conditions are 10C/min, flow rate of charging gas is ~25ml/min (filling gas is sometimes used as nitrogen).

[Another method is to measure weight loss by setting it to a specific temperature (polymer processing temperature, Isothermal TGA test).]

In general, weight loss (volatility) is directly related to the molecular weight of the additive and not to the melting point. However, there are some exceptional cases, which may occur when the additive molecules have strong polar forces against each other.

In the actual use process, when the additive is melted and mixed into the polymer, only the additive on the surface of the polymer volatilizes, so it can generally be used by raising the processing temperature up to T10 (temperature at which 10% of the weight is lost). If absolutely necessary, after confirmation, it can be used at 50C below the T10 temperature. In some cases, it can be used without problems at high processing temperatures.

Therefore, when selecting additives suitable for polymers with high processing temperatures, check TGA data before selecting.