Surface modification to improve powder bulk behavior under humid conditions

• Humidity affects the flow and packing properties of corn starch.
• Surface modification using hydrophobic nano-particle results in improved and consistent powder bulk properties at all RH conditions.
• Surface modification helps in reducing interparticle frictional forces at low RH and prevents capillary bridges at high RH.
• Study indicates that surface modification can produce humidity-resistant fine powder.

Humid environment often creates various problems in fine powder processing and frequently poses a substantial threat to the final product quality. The present study focuses on improvement of bulk behavior of fine powder under humid environment using surface modification. Corn starch powder was surface modified using Aerosil R972 grade of hydrophobic nano-silica through dry coating. It was found that flow and packing properties of uncoated powder deteriorated at elevated relative humidity (RH) conditions with prominent changes observed above 60% RH. Also, at low RH conditions (30%), increased interparticle frictional forces owing to the diminished lubricating moisture layer resulted in decreased flow of uncoated powder. In contrast, surface-modified powder exhibited resistance to such detrimental effects of moisture loss and gain at low and high RH respectively. The present study showed that surface modification of powders helps to reduce the interparticle cohesion in fine powders and prevents the detrimental effects of humidity on its bulk behavior.

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