Solution Processing of High Particle Loading Polymer/Particle Mixtures

Materials with high particle loadings are important for several applications: in many cases the particles provide the desired functionality and the polymer acts to bind them together into a shape, so maximizing particle content is required. As new processing technologies become more prevalent, such as 3D printing and electrospinning, low binder content has introduced challenges, particularly due to the high viscosities encountered in highly loaded systems. Understanding the rheology and the effect of chemistry and molecular interactions on the processability is of great importance to the field.

We have focused primarily on two processing technologies: additive manufacturing (AM, direct ink writing 3D printing) and electrospinning. We focus on direct ink write additive manufacturing and examine the rheology and processability of high particle loading suspensions (>60 vol% particles) and show how the nature of the polymer binder, the particle size distributions and the processing parameters influence the consistency of the print and the distribution of particles and voids in the final solid part. This work will allow us to understand how to design high solids suspensions for direct ink write additive manufacturing to result in homogenous, predictable solid parts for applications ranging from pharmaceuticals to concrete to ceramics.

In a parallel project for preparing highly functional ultrafine fiber mats, we have developed the electrospinning process to prepare fibers containing high loadings of particles, again, with particular attention to rheology and molecular level behavior.