Influence of drying conditions on the stress and weight development of capillary suspensions

TL;DR

This study investigates how drying conditions affect stress and weight development in capillary suspensions, showing they dry more uniformly with lower stress, reducing cracking risk without additives.

Contribution

It demonstrates that capillary suspensions inherently resist cracking during drying due to strong particle networks formed by capillary bridges, independent of dry film porosity.

Findings

Capillary suspensions exhibit lower peak stresses during drying.

Increasing relative humidity enhances stress resistance.

Higher boiling point secondary liquids offer better drying control.

Abstract

Cracking of suspensions during drying is a common problem. While additives, e.g. binders and surfactants, can mitigate this problem, some applications, such as printing conductive pastes or sintering green bodies, do not lend themselves to the use of additives. Capillary suspensions provide an alternative formulation without additives. In this work, we use simultaneous stress and weight measurements to investigate the influence of formulation and drying conditions. Capillary suspensions dry more homogeneously and with lower peak stresses, leading to an increased robustness against cracking compared. An increase in dry film porosity is not the key driver for the stress reduction. Instead, the capillary bridges, which create strong particle networks, resist the stress. Increasing the relative humidity enhances this effect, even for pure suspensions. While lower boiling point secondary liquids, e.g. water, persist for very long times during drying, higher boiling point liquids offer further potential to tune the the drying process.