Moisture bonding in powders

The Influence of Relative Humidity on Particle Adhesion – a Review of Previous Work and the Anomalous Behaviour of Soda-lime Glass

“…For the smoothest surfaces considered (RMS roughness 0.2 nm), the transition occurred at an RH of approximately 25%, rising to a value of 65% for a surface with an RMS roughness of 3 nm. Rabinovich et al acknowledge the work of Coelho and Harnby [39,40] in predicting this critical humidity from a thermodynamic perspective involving the BET model for water sorption coupled with the Kelvin equation for liquid bridge stability. However, this model typically results in a critical RH in the region of 70 Ҁ 99%.…”

Dry powder inhalers: Physicochemical and aerosolization properties of several size-fractions of a promising alterative carrier, freeze-dried mannitol

“…498 Low moisture uptake is generally considered advantageous in 499 DPI formulations. This is because moisture uptake can decrease 500 the dispersion performance of the formulation due to capillary 501 forces that could lead to agglomeration (Price et al, 2002) or fusion 502 between fine particles and large particles through solid-liquid 503 bridge formation (Coelho and Harnby, 1978). In addition, the pres-504 ence of free water can affect the stability of particle surface micro-505 structure by a dissolution-precipitation process (Finot et al, 1996).…”

The Influence of Mechanical Processing of Dry Powder Inhaler Carriers on Drug Aerosolization Performance

“…For example, storage of samples at elevated humidities may allow water vapor to condense in the capillaries that exist between individual, with increased levels of fine particles resulting in an increased number of capillaries. 28,29 Furthermore, highly soluble materials, such as lactose monohydrate, may undergo limited dissolution at interparticulate contact points with subsequent solidification, thus resulting in solid-liquid bridge formation between particles, leading to particulate fusion. 30 Similarly, such particle fusion could be facilitated by the presence of amorphous content on particulate surfaces recrystallising at elevated humidity.…”