Modelling, Validation and Application of Triboelectrification

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Collisional and sliding contacts of two different materials are commonly associated with electric charge transfer, leading to charge accumulation. This causes an overwhelming number of handling and processing problems and explosion hazards, thereby degrading manufacturing efficiency and causing out of specification products and wastage. Examples are strong adhesion to containing walls and deposition in pipes, impairing flowability and aggravating segregation of components in a mixture, thereby upsetting formulations. It is common to experience highly active drugs filling up a spiral jet mill (thereby upsetting its functioning), components of a formulation preferentially depositing on grounded surfaces, getting concentration spikes of minor components of a formulation, poor powder spreading due to charging in additive manufacturing. In contrast, the phenomenon has been used to good effect in xerography and more recently for Tribo Electric Nano Generators (TENG). Despite being known for millennia, the triboelectrification phenomenon is not well understood and actually not predictable for non-metallic surfaces. The role of environmental humidity and temperature adds to the complexity. Considering its importance in advanced manufacturing of new materials, for which little material is initially available, a timely project with internationally leading-edge participation is proposed to tackle triboelectrification from a molecular level solid-state formation, right up to large scale manufacturing of active pharmaceutical ingredients and polymers. The project has seven industrial partners and six international collaborators from Japan, Brazil, Italy and Canada, contributing to seven work packages, each addressing a topic of scientific as well as industrial interest. The activities range from molecular solid-state level work function calculations by Density Functional Theory, to particle charge transfer characterisation by developing specialised instruments for charge distribution measurement and TENG, to unit operation level, including fast fluidisation and risers, pneumatic conveying and cyclone separation. The work is of strategic interest in manufacturing, ranging from pharmaceuticals, foods and plastics to additive manufacturing. It will have a huge impact on manufacturing sustainability, as the mitigation of triboelectrification issues will have a notable reduction in wastage and environmental footprint, and on the performance and material optimisation for the fast growing new technology of TENG. The proposed programme will tackle six challenges as addressed in the Case for Support.