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Homogenizers vs High Speed Immersion Blenders - is there a practical difference?
I’m looking at some formulas using various zinc oxide dispersion from DOW, Kobo and Umicore primarily. Interestingly their sample formulas suggest anything from just paddle mixing to homogenization for 3 minutes or until “desired particle size has been reached” (assuming you have access to a scanning electron microscope to make sure you’re where you want to be).
I’m wondering, for bench test formulation, can your typical 12000 rpm immersion blender provide the same ability to break up and evenly disperse agglomerated mineral particles as your typical 20000 rpm homogenizer? It it mostly a function of time, or is is there some qualitative difference between the methods?
Then further down the line, what equipment does most OTC-ok CMOs use?
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5 Replies
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A little clarification would be nice. At what scale are you making this? The difference between immersion blenders and Homogenizers is one of shear. Most immersion blenders use high speed to produce shear, but because this is typically done with a spinning blade shear levels are relatively low and dont work to well for scaling up. Homogenizers on the other hand don’t run quite as fast (typically 2000-5000 rpm) but they produce greater shear force by the fact that its a blade inside a cage that forces liquid through holes (kind of like putting your fist in the palm of your other hand and grinding. This action can force smaller particle sizes. This is also more scaleable as many homogenizers can be used “in-line” through a pump and hose that gets recirculated.
Also due to the fact that the “particle size” that is being referenced in these procedures most likely is describing oil droplet particle size for creating stable emulsions, you can estimate this size by using a simple 100x light microscope. These can be purchased for as little as $250 on Amazon.
If you are making small lab / hme batches an immersion blender should work fine. If you are paying a CMO to do the work ensure they have a homogenizer on hand.
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Thanks for the thorough response, this makes sense.
I’m doing small scale test formulations, so in that case it’d seem a immersion blender could suffice. I do check with my CMOs regarding their equipment.
As for particle size, what intersts me is mainly pigment particle size, either for color cosmetics or sunscreen formulation - would e.g https://www.amazon.com/AmScope-M160C-2L-PB10-E2-Magnification-Illumination-Battery-Powered/product-reviews/B00H7RMHTG/ref=cm_cr_dp_see_all_btm?ie=UTF8&showViewpoints=1&sortBy=recent be of any use for looking at emulsions with ZnO to see how big the particles agglomerates are?
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To provide some additional color for people who may stumble upon this old question (as I have), there is an immense practical difference between an immersion blender (or any blender) and a homogenizer.
Blenders use fast-moving blades to reduce particle size. They primarily impact particle size through cutting, and secondarily through shear forces.
Homogenizers pull the material into a very small gap between a central, very rapidly spinning rotor and a stationary outer shaft (the stator). Because of the massive difference in speed between those two parts, it creates huge amounts of shear forces.
While a very high-quality immersion blender may approach the RPMs of rotor-stator homogenizers, because the blade of the blender is essentially operating in open space, the shear force is relatively limited. It is the shear force which really gets small particle sizes. With a bladed instrument, you’re mostly relying on how small of a particle the blade can meaningfully impact before it simply gets pushed out of the way before impact due to fluid flow. The design of a rotor-stator actively sucks liquid up into the high-shear area in the probe.
A good immersion blender will provide a particle size of perhaps 100 µm (1/10th of a mm). A good homogenizer and probe can achieve particle sizes below 5 µm (1/200th of a mm). So the particle size will be quite different, and the smaller your particle size, the smoother and more stable your emulsion will be.
Of course, rotor-stators aren’t the only type of homogenizers. You can read about the use of other homogenization technologies in emlusification here: https://homogenizers.net/pages/ac-emulsification
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Beautiful explanation. I am just baffled why the beginner sites promote stick blends as instruments of shear. Especially when for a few dollars more, they can buy a tool that gets quite close to your explanation, from Dynamic/Misceo.
I will enclose a picture of the head from my Dynamic….so people can view the tolerance between the bell and hammer.
I will also mention… Silverson has numerous videos on YouTube that show (but don’t explain well) some of these differences.
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Neat device! I’d be curious what a particle size analysis on something it processed would tell us.
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