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混和型研磨仪 Fast homogenization of small sample volumes

Mixer mills grind and homogenize small sample volumes quickly and efficiently by impact and friction. These ball mills are suitable for dry, wet and cryogenic grinding as well as for cell disruption for DNA/RNA or protein recovery. For special applications such as mechanosynthesis, they offer unique solutions. Mixer mills are well known for their ease of use and small foot-print compared to other types of ball mills.

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Mixer Mills - Function Principle

The grinding jars of mixer mills perform radial oscillations in a horizontal position. The inertia of the grinding balls causes them to impact with high energy on the sample material at the rounded ends of the jars and pulverize it. High energy milling is possible by operating at high frequencies up to 35 Hz. The movement of the jars and balls causes further size reduction effects through friction and additionally leads to effective mixing of the sample. The degree of mixing can be increased by using several smaller balls. 

Mixer Mills - Fields of application

Mixer mills are used for the pulverization of soft, hard, brittle, and fibrous materials in dry and wet mode. With their small footprint, ease of use, and very short processing times, they are true allrounders in the laboratory.

Mixer mills are ideally suited for tasks in research like mechanochemistry (mechanosynthesis, mechanical alloying and mechanocatalysis), or ultrafine colloidal grinding on a nanometer scale, as well as for routine tasks such as mixing and homogenizing.

They are also widely used for cell disruption for DNA/RNA extraction via bead beating. Up to 240 ml of cell dispersions can be processed for protein extraction or metabolome analysis.
A crucial advantage of mixer mills is their great versatility – in some models combined with the capacity to actively cool or heat material, allowing for more controlled configurations than in other ball mills. In the field of mechanochemistry, the possibility to control the reactions inside the jar is very beneficial.

Depending on the models, temperatures down to -196°C or up to 100°C can be applied. Mixer mills are available with 1, 2 or 6 stations. Jars and balls are available in various sizes, designs and materials.

典型样品材料 - 氧化钛

氧化钛 
湿磨

典型样品材料

金属合金
干磨

典型样品材料: 头发

头发
干磨

典型样品材料:轮胎橡胶

轮胎橡胶
冷冻研磨 莱驰研磨仪

Mixer Mills - cooling and heating options

CryoMill 设计专用于 -196°C 的低温研磨,而 MM 500 control 的工作温度范围为 -100°C 至 +100°C,温度调节范围为 -100°C 至 0°C。

降温的好处包括, 例如:

  • 保护对温度敏感的分析物,如挥发性物质或药品和食品成分
  • 脆化无法在室温下粉碎的样品材料
  • 湿法研磨,以保持低于一定温度(在某些情况下可低于室温)
  • 机械化学反应中,停止反应并稳定中间产物,使最终产品与未冷却时的结果不同
如果在加工过程中加热样品材料,某些应用会得到改善,例如:
  • 制酱(食品工业)
  • 强化机械化学反应
所需温度和操作设置取决于具体应用。

Mixer Mills - Grinding jar and ball materials

如何选择最合适的材料?

The material of the grinding tools needs to be selected with the subsequent analysis in mind. If, for example, a sample is analyzed for its heavy-metal content, the abrasion of a steel jar and balls might introduce chromium into the sample which would lead to falsified analysis results. Consequently, only a metal-free material like zirconium oxide is suitable for the purpose.

The material of the tools also has an impact on their efficiency. The two most important aspects are:
  • Energy input (related to the density of the material)
  • Hardness

能量输入

The higher the density of a material, the higher is the energy input. This means that the acceleration of, for example, tungsten carbide grinding balls at a given speed is higher compared to jar and ball materials of lower density. The energy input is higher when the ball hits the sample, causing a better crushing effect which is beneficial for pulverizing hard-brittle samples.
For soft materials, on the other hand, too much energy input may prevent effective crushing. In such cases, the sample is not really pulverized into a fine powder but rather forms a layer that sticks to the jar walls and covers the balls. Homogenization is not possible that way and sample recovery is difficult. That is why for soft materials other mill types, for example rotor mills, are better suited.

硬度

要找到硬度合适的罐和球材料,考虑因素很简单:材料的硬度必须高于样品的硬度。如果材料硬度较低,磨球就会被样品材料的颗粒磨碎。

不同材料的研磨工具

不建议使用不同材料的配件。例如钢制研磨罐搭配氧化铵材质的研磨球,首先,两种材料的磨损都会影响分析结果,其次,会加速配件的磨损。

Mixer Mills - Jar types and sizes

Classic mixer mills work with screw-top jars which are designed for quick handling and pulverization of small sample amounts. The jars are available in hardened steel, stainless steel, tungsten carbide, agate, zirconium oxide, and PTFE.

The MM 500 nano and MM 500 control are operated with screw-lock jars. These jars are pressure-tight up to 5 bar, the integrated safety closure allows for convenient handling. The new jar design is very beneficial for wet grinding and pulverizing fibrous samples like hair.

Thanks to the flat lid, the nominal volume can be fully used, for instance when milling fibrous samples, or to ensure the optimum mixture of material, small balls and liquid for wet grinding.

Available materials include hardened steel, stainless steel, tungsten carbide and zirconium oxide ensuring contamination-free processing. Aeration lids for all mixer mill jar sizes and materials are available, e.g. for processing under inert atmosphere.

Screw-top jars
Screw-lock jars

1. Screw-top jar
2. Screw-lock jar 
3. Filling volume

Screw-top jars MM 400, MM 500 vario, CryoMill Screw-lock jars MM 500 nano, MM 500 control
不同的研磨罐材质 7 (4) 4
研磨罐尺寸 1.5 | 5 | 10 | 25 | 35 | 50 ml 50 | 80 | 125 ml
Aeration lids
GrindControl
Integrated safety closure
适用于干磨
Suitable for wet grinding Limited - jar design is not optimal for applying the 60% filling rule Yes, designed to apply the 60% rule
纤维样品研磨 Yes, very easy handling, as the lids are flat and the full volume of the jar can be used to fill in voluminous sample

Mixer Mills - Recommended jar fillings

用于干磨

干磨时,通常采用所谓的三分之一规则来获得最佳效果。也就是说,大约三分之一的罐子容积应该装满研磨球。根据这一规则,球越小,就越需要装满三分之一的罐子。另外三分之一的罐子容积应装满样品材料。

根据这一规则,既能提供所需的粉碎能量,又能在罐中装入足够的样品材料以防止磨损;

用于干磨

1.三分之一的自由空间
2.

用于含纤维的样品

对于纤维材料或粉碎后体积急剧下降的材料,建议使用较高的样品填充量。罐中需要有足够的材料以减少磨损。如有必要,可以在几分钟后添加更多材料,以保持所需的最小体积;

用于含纤维的样品

1.三分之二的样品
2.

用于湿磨

要生产粒度小至 100 纳米或更小的颗粒,需要湿磨和摩擦,而不是冲击。要做到这一点,需要使用许多表面大、摩擦点多的小球。因此,干法研磨工艺中推荐的三分之一填充量被 60% 规则所取代,即 60% 的罐子中填充小球。样品量应约为 30%。首先将小球加入罐中(按重量计!),然后加入材料并混合。最后仔细混合分散剂液体。

用于湿磨

1.六分之一到三分之一的样品 + 液体
2. 三分之二的研磨球

如何选择合适的研磨球尺寸

To ensure that the grinding balls rapidly pulverize the sample, they should have at least three times the size of the biggest sample piece. Typically, a factor of approximately 1000 can be applied to ascertain the suitable ball size for the intended final fineness. If a grind size of 30 µm (D90) is the objective, ball diameters between 20 mm and 30 mm are best suited. If smaller particles are required, a second process step with smaller balls is required.
As larger balls could crush smaller ones, it is not advisable to combine different ball sizes in a single milling process. 

Wet and Nanoscale grinding in mixer mills

Nanotechnology deals with particles in a range from 1 to 100 nm. These particles possess special properties due to their size, as their surface is greatly enlarged in relation to their volume (so-called “size-induced functionalities”). Ultrafine particles are, for example, harder and more break-resistant than larger particles.

Small particles tend to get charged on their surfaces and agglomerate during dry grinding, which is a limiting factor for size reduction. For nanoscale grinding, liquid or dispersant is used to keep the particles separated and salt solutions help to neutralize the surface charges. Long chain molecules in the liquid can keep the particles separated thanks to steric hindrance.  

Aeration lids from RETSCH

Aeration lids have been engineered to improve both the efficiency and safety of grinding processes in laboratory environments. They are especially beneficial when working with materials that require a controlled atmosphere—such as during wet grinding or when handling reactive substances. In such cases, the internal atmosphere, including oxygen, can be replaced by flushing the jar with an inert gas like nitrogen.

These lids also enable the introduction of gases directly into the grinding jar, which is essential for certain chemical reactions or for maintaining an inert environment. The jars can be pressurized up to 5 bar, which may help facilitate the incorporation of gas molecules into the reaction during milling.

Additionally, aeration lids allow the grinding jar to be connected directly to an analyzer—either after operation in a planetary ball mill (or in the Emax) or even during operation in the MM 500 nano or MM 500 control. This setup makes it easy to analyze gases released during grinding processes or generated by chemical reactions. The lids are equipped with inlays made from various materials—such as stainless steel, zirconium oxide, and tungsten carbide—allowing the same lid to be used with different jar types.

混和型研磨仪 - 常见问题

What is a mixer mill?

Mixer mills belong to the family of ball mills and are characterized by their small footprint, fast processing times and great versatility.

They are used for mixing, pulverizing and homogenizing hard, medium-hard, brittle, soft, elastic and fibrous sample materials.

Size reduction is effected through impact and friction. Mixer mills from Retsch are available with one, two or six grinding stations.

Which applications require a mixer mill?

Mixer mills are used for dry, wet and cryogenic pulverization of small sample volumes within seconds. They generate the required energy input for nanoscale grinding.

A typical field of application is cell disruption by bead beating for DNA/RNA and protein extraction.

Mixer mills are also frequently used in the field of mechanochemistry, particularly those models which provide cooling and heating options. 

How does a mixer mill work?

Sample material and grinding balls are filled into the jar which is clamped into the mill. The radial oscillations performed by the mill lead to the pulverization by impact and friction of the balls. The sample is also thoroughly mixed by the movements of jar and balls.