(18a) Understanding Adhesive Mixing Via Energy-Based Stick/Bounce Model

An energy-based stick/bounce model is presented to explain
relationships between particle interactions dominated by Van-der-Waals
force during mixing of fine and coarse particles at different mixing
intensities. The investigation concerns examination of the adhesive mixing
efficiency (Kq)
based on relative magnitudes of Van-der-Waals energy, dissipated
energy, de-agglomeration energy and relative kinetic energy during impacts.  Kq>1 indicates good adhesive mixing
efficiency, while  Kq<1 indicates poor adhesive mixing
efficiency. Effect of size, material properties and mixing intensity of fine
and coarse particles are investigated to attain a deep understanding of the
mechanisms of adhesive mixing. Most interestingly, larger coarse particle size
leads to larger agglomerate size of fine particles. Larger fine particle size
and high intensity both lead to poor adhesive mixing efficiency. Size of fine
particle agglomerates was also considered
in the model. De-agglomeration energy was found to be highest amongst other
energy terms during processing, indicating the de-agglomeration step was the
most energy consuming step of adhesive mixing. The experimental results using
a vibrational mixer and two sizes of fine (silica and cornstarch) and several
sizes of coarse particles (KCl and cornstarch) validate
the modeling as it explains various mechanisms. The guest silica
particles tended to attach to the host KCl particles with a good adhesive mixing
efficiency, while the guest cornstarch
particles tended to detach from the host KCl particles beyond certain mixing intensity.  Also, larger KCl
particles would lead to the larger agglomerate size of cornstarch, indicating
the poorer mixing efficiency. Finally, higher intensity leads to the worse
mixing efficiency.