EDITOR ’ S CHOICE HOW TO CHOOSE A MIXER
INTERTRONICS
Achieving a fast , repeatable mixing process without air bubbles
Choosing the correct mixer with the right capabilities will often depend on the materials you need to mix — how prone are they to retain air ( perhaps due to high viscosity ), how much air is already trapped in them , how much air is brought into the mix from the powders you are adding , etc . Planetary centrifugal mixers typically have three types of function or capability to help you mix your liquids , pastes and powders , with complete uniformity and without air bubbles . Here Steve Yeomans , Marketing Executive at adhesives specialist Intertronics , explains how to choose a mixer .
A simple blend of low viscosity liquids may very well mix easily with no visible air bubbles . More complex mixes involving differing viscosities and / or powders will be more difficult to achieve an airfree mix without extra help . For critical applications , where even micro-bubbles are unacceptable , then mixing under vacuum may be required .
THE MIXING PRINCIPLE
The fundamental and common technology of all the THINKY range is “ planetary centrifugal mixing ”. This mixing action does not use blades , paddles or other invasive tools . The technique involves rotating containers around their central axis , at a 45 ° angle , whilst at the same time revolving them around a central point ; similar to the
way the earth moves around the sun , giving us both days and seasons . In the THINKY , these rotations and revolutions are very fast ; ~ 1,000 ’ s of RPM . This generates mixing forces of about 400G , giving powerful material movement in the container . The ratio of revolution to rotation is critical to providing the optimal mixing forces .
The technology results in a fast , fully homogenous mix and , unlike machines that rely on the insertion of paddles or impellers into the material , no air is introduced ; in fact , the shear forces finely disperse any entrapped air , and there is a tendency for it to be removed (“ squeezed out ” to the surface ).
PLANETARY MIXING
Planetary mixers , including the THINKY ARM-310 , offer significant productivity improvements over typical hand mixing techniques . Able to homogeneously disperse engineering compounds such as adhesives , sealants , lubricants , cosmetics , or pharmaceuticals in seconds to minutes , they provide consistent mixing results every time . Mixing takes place in removeable containers , meaning there is no mess to clean up after a mixing process , thereby saving valuable time and avoiding cross contamination .
DEGASSING
While the mixing revolution and rotation action will not add any air to your materials during mixing , and in fact is likely to remove them , it is possible for entrapped air to remain after a normal mixing step . Models such as the THINKY ARE-250 have an additional “ defoaming ” or “ degassing ” mode , where the ratio of revolution to rotation is altered to favour the revolution component , generating high centrifugal forces on the materials — up to 510G . The lowest density contents , air bubbles , rise to the surface of the liquid and are destroyed by shearing forces of the slower rotation .
28 PECM Issue 52