Polymer powders are increasingly used in Additive Manufacturing (AM) processes, with for example powder bed fusion and binder jetting additive manufacturing technologies. In these applications, assessing the spreadability/flowability of powders is essential to ensure good and consistent quality of the additively manufactured parts. Over the recent years, it has become increasingly reported that characterizing powders under process relevant conditions is mandatory. Nevertheless, most flow analysis techniques are still carried out at ambient temperature. Therefore, there is a crucial need for new characterization techniques allowing to measure the performances and the flow properties of powders at high temperature. Especially for additive manufacturing, in which polymer powders are spread at elevated temperature.

In this study, we present a new method for measuring the flow properties of powders and granular materials at elevated temperature. We show the dramatic influence of the temperature on the flow properties and packing dynamics of different polymer powders (amorphous and semi-crystalline), even far below their glass-transition (Tg) or melting (Tm) temperature. Finally, we show that the parameters obtained from the packing curve measured at different temperatures allow extrapolating the temperature corresponding to the onset of caking. This study highlights the critical influence of the temperature in an additive manufacturing process and the need for appropriate testing under relevant conditions.