Determination of the glass transition of powder samples using Dynamic Mechanic Analysis on compacts

Magazine article, 2010

Dynamic Mechanic Analysis, DMA, is a sensitive method to determine the glass transition temperature (Tg) of materials. Several different sample geometries such as three point bending, stretched films or compressed cylinders, are commonly used. The Tg of a powder is related to its “sticky point”, i.e. the temperature when the powder particles interact instead of flowing freely. The determination of powder Tg is not straightforward using DMA due to the limiting geometry. Here it is demonstrated that the Tg of powder samples can be effectively and correctly determined by DMA on compacts in compression mode, using a standard wedge shaped probe usually utilized in three point bend analysis. The analysis of compacts holds the benefits of analysing powder samples as received from manufacturers, being relatively robust with regard to deformation as the material becomes rubbery, and enabling easy sample preparation and handling.