Filler impact on resin viscosity
Resins are often mixed with fillers to obtain specific properties. During the mixing process, the fillers of the powder are dispersed in the liquid resin. From the microscopic, this is a process of liquid wetting the solid surface. The moisture on the powder surface, the shape of the powder and the surface roughness will affect the resin wetting the powder result(Figure 1). In general, the viscosity of the initial mixture product is relatively high as time goes by the viscosity and it often decreases slightly. Excluding the changes in forces of powder, a reasonable explanation is that the surface was not completely wet and further wetted therefore the flow resistance became smaller. This is the reason that the viscosity was decreased. When the added amount is high, the soaking behavior has different results: It exhibits high viscosity fluid when initial mixture, because it has residual temperature(Figure 2). After standing for a period of time, the sample became "dry out", and it will not recover after re-stirring (Figure 3). From the microscopic, the resin barely disperses the particles, so it can flow (Figure 4). Some resins further wet the surface when standing. The liquid adsorbed on the particle surface is difficulty with flow. The liquid can move between the particles is less, even difficult to fill the gaps between the particles. The powder getting stuck and lose fluid, so it looks like dry lumps (Figure 5).
impact on resin viscosity
─ By Chia-Ying, Chiu