Dave Dickey Forum Moderator 275 Posts
Re: Redesigning the impeller blade for a batch polyurethane tank27 May 2008 at 1:29pm
You have not given me enough information to really answer your question. The batch size and viscosity only tell half of the story. The impeller size and rotational speed are essential to understand the mixing intensity.
However, if you are pulling air into your polymer with a propeller, you are probably doing something else wrong. At those viscosities, you cannot use a center-mounted mixer without baffles. If you don't have baffles in the tank, then the mixer must be mounted at an angle and aimed so a vortex is not formed. If you have a vortex and drawing air in with a propeller, you are going to have the same problem with other impeller types, unless you just have too much mixing. A vortex on the surface usually means that you have poor mixing without much top-to-bottom motion. Any air incorporation further hurts the mixing.