First Mixer Mill Worldwide with the Power of a Planetary Ball Mill

In this interview, AZoM talks to Dr. Tanja Butt from RETSCH GmbH about the world's first mixer mill to have the power of a planetary ball mill.

Can you give a brief overview of RETSCH, the work you do, and the markets you serve?

Retsch is the worldwide leading provider of lab-scale solutions for size reduction and particle sizing technology. The product portfolio includes various types of mills, crushers and grinders as well as analytical sieve shakers and test sieves. As our instruments are mainly used for quality control of solid materials, you can find our machines in almost any industry. To name but a few: Food & Feed, Environment, Material Science, Glass/Ceramics, Chemistry, Pharmaceuticals, and many more.

How does the Mixer Mill 500 compare to alternative mixer mills?

The most prominent feature of the new MM 500 is that it operates with a frequency of 35 Hz. Other mixer mills usually have a frequency of 30 Hz or even less. The effect of the extra 5 Hz is very impressive for high-impact applications where hard-brittle samples are pulverized within minutes. This is also true for cryogenic grinding of tough/elastic samples.

What other benefits does the Mixer Mill MM 500 have?

The innovative Screw-Lock jar design in combination with the new clamping system make the handling of the mill very easy. Clamping the jars is done in a few seconds. The jars can stay clamped for taking sub-samples or visual checks of the particle size. This is a unique feature of the MM 500; in all other balls mill, the jars have to be removed for intermediate checks. The grinding jars come in sizes of 50, 80 and 125 ml. They are pressure-tight up to 5 bar which makes them ideally suited for mechanochemical applications or wet grinding. Moreover, due to the flat lid these jars allow for full exploitation of the jar volume, something which is not possible with the jars of other mixer mill types. These usually have part of the volume inside the lid, hence it is difficult to fill in enough fibrous sample material or, for efficient nano grinding, enough small grinding balls plus sample plus liquid.

The Mixer Mill MM 500 is also stated to be a real alternative to classic planetary ball mills, why is this the case?

What’s unique about the MM 500 is that performance, handling, application fields and design make it a combination between a classic mixer mill and a planetary ball mill.

When it comes to long-term grindings of several hours with high energy input to obtain particle sizes <1 µm, Planetary Ball Mills have been the instruments of choice so far. Despite their benefits for this type of application, they have the drawback of requiring cooling breaks and are not as easy to handle as mixer mills.

Thanks to the maximum frequency of 35 Hz, the MM 500 possesses the crushing power to produce particles in the nanometer range. It accommodates 2 grinding jars sized 50 ml, 80 ml or 125 ml and with its suitability for long-term grinding processes up to 99 hours without cooling breaks, it is a real alternative to planetary ball mills – with all the benefits a mixer mills offers like comfortable handling and substantial time savings thanks to less warming effects.

Could you please explain the basic theory behind how your Mixer Mill MM 500 can crush samples to the nanometer range?

In mixer mills, the grinding jars perform radial oscillations in a horizontal position, usually with a maximum frequency of 30 Hz or less. The number and size of the grinding balls determines the predominant grinding mechanism: using one large and heavy grinding ball leads to the high-impact mode, i. e. the ball hits the rounded ends of the jar with high impact. The high-impact mode, which allows for very fast pulverization, is unique for mixer mills and is intensified in the MM 500 by the high frequency of 35 Hz. Using a number of balls with smaller diameters generates high friction between grinding balls, jar walls and sample material. This high-friction mode is a prerequisite for producing nanosized particles. Another prerequisite is the use of grinding balls Ø 3 mm or smaller to obtain enough surface and friction points between the balls to produce nano particles. The smaller the balls, the finer the resulting particles.

What other applications does the Mixer Mill MM 500 cover?

The MM 500 is suitable for dry, wet and cryogenic pulverization of soft, hard, brittle, fibrous and elastic sample materials for subsequent analysis. With its ability to deliver high energy input at 35 Hz, it is also suited for mechanical alloying processes to produce new materials or for chemical reactions in mechanochemistry applications.

What’s next for RETSCH?

We’re continuously striving to develop instruments and solutions which make our customers’ work in the lab easier, safer and more efficient. An example for this is the new Retsch App which will soon be available for some of our mills including the MM 500.We will continue to revise and extend our product offering and provide users worldwide with a wealth of application information and support.

New product releases are scheduled for 2020, so I recommend signing up to our customer newsletter to stay informed.

About Dr. Tanja Butt

Dr. Tanja Butt studied Biology at the University of Duesseldorf, Germany, and graduated with a Diploma in Biology. After that she earned her PhD in biotechnology at the Forschungszentrum Juelich, Germany. Later, she worked in R&D and project management for different institutions. She joined Retsch in 2013 as Product Manager for the whole milling and sieving product range.