Article by: Guest Author
Author: Bob Wilcox
We’ve noted several posts in the Chemists Corner discussion forum on using homogenizers to prepare shampoos. Our take on homogenizers is primarily from the R&D perspective — that is how lab homogenizers can help researchers develop processes that can be scaled to production levels. And while lab homogenizers have the capability of handling relatively large samples — up to 20 liters for the larger models — those with capacities of from 0.1 ml to 5 liters are probably more useful for preliminary research.
What are homogenizers
Homogenizers are part of a family that includes overhead stirrers and magnetic stirrers. What homogenizers bring to the bench are vigorous stirring and mixing action but at controllable speeds. In fact, just about any composition that can be mixed can be processed by these versatile tools.
We won’t dwell here on where you can employ these tools in the cosmetics lab, but instead describe how they work and the various homogenizing configurations that are available to do the job properly. Among these jobs are included cell disruption, emulsifying, dispersion, dissolving, mixing, suspending, and — with special accessories — in-line processing, grinding and particle reduction.
Lab Homogenizer Components
Lab homogenizers are powered by a drive motor, the size and power of which is determined by the task at hand. Power ranges from 125 watts in smaller models up to 1700 watts. The motors power a rotor shaft (much as an electric drill powers the bit) at controllable speeds as high as 45,000 rpm.
Attached to the working end of the shaft is a removable rotor of sharply machined teeth designed to perform specific homogenizing functions. The rotor shaft fits inside a stationary tube that is attached to the drive motor housing. At the base of this tube is a removable stator with sharply machined slots that are compatible with the specific rotor selected. The rotor-stator combination is called the generator. All of these components — tubes, shafts and generators — are of corrosion resistant stainless steel.
Got that? Rotors and stators can be changed out to achieve different configurations that perform different tasks. The only “but” is compatibility with the tube diameter.
Although there are hand held models, homogenizers are generally affixed to an adjustable mounting stand for correct positioning in the sample container and to assure stable operation during long mixing cycles.
So, an Example Please….
OK, just one. Our highest-speed homogenizer drive, the 350-watt CAT X360 will handle sample volume sizes from 0.1 ml to 2 liters based on shaft sizes. This makes it an excellent choice if your operations call for super-fine disintegration or if you are looking to process larger volume samples on a laboratory scale.
With a design speed of 45,000 rpm the CAT X360 can be connected to the optional P1500 variable speed control allowing researchers to set rotor speed between 10,800 to 42,500 rpm. Other optional equipment include the highly recommended drive stand and clamp plus wrenches to attach and remove rotors and stators.
And by the way, the homogenizers start slow then ramp to the assigned speed to avoid splashing contents about the work area.
More Important is What you are Mixing
As noted, generators are available in several configurations. Stator tubes and rotor shafts are selected based on length and diameter, which relate primarily to the size of your mixing container. The third criterion relates to the physical characteristics of what you are mixing. We broadly classify these as viscous or coarse samples, low viscosity materials, fine or aqueous materials and knife or cutting applications. When activated the homogenizer draws your samples up through the open base of the generator assembly and violently propels it through the knife edge of the stator.
As suggested above other mixing configurations are available. One supports in-line processing by drawing material from one container, homogenizing it and discharging it into another container. This is accomplished by using flow through chambers available in two sizes. The homogenizing principle is the same but the generator assembly is within the chamber. Dwell time in the chamber can be controlled by restricting the outlet flow, and a closed-loop system is produced when the material is withdrawn from its container, processed and returned to the same container.
A third configuration is achieved by attaching the homogenizer drive motor to an analytical mill designed to quickly perform size reduction on a small scale for a variety of organic and inorganic materials in preparation for further analysis. Particle size reduction is accomplished using small sample sizes such as 180 cc or about 11 cubic inches. Disintegration of the material being tested is usually quite rapid but depends somewhat on the hardness of samples being processed.
To conclude, homogenizers are quite versatile tools in themselves and even more so with special attachments. If high speed mixing, dispersing, blending or other actions are required in your cosmetics laboratory consider how these tools can help.
Need more info? Check the homogenizer category for a guide to components and accessories.
Bob Wilcox has represented CAT Scientific’s family of homogenizers, magnetic stirrers, liquid metering and related laboratory equipment since 2002. In addition to heading the sales function in the US he is chief technician for the CAT equipment service organization.