Physics refers to the gradual grinding down or wearing away of material through abrasion or friction, as attrition. In pharmaceutical engineering, attrition mills are often used to reduce the particle size of ingredients to enhance the bioavailability and solubility of drugs. Attrition milling involves accelerating particles at high speeds into a surface section of the mill, while also causing them to collide against each other. These interactions between constituent particles and the mill’s surfaces during processing produce greater uniformity within attrition mills, reducing particles to 100 mesh (149 microns) and finer.  

What Are Attrition Mills & How Do They Work?

Attrition mills mechanically reduce bulk solids through intense agitation. Equipped with a stationary disc on its exterior and a revolving disc on its interior, attrition mills can be adjusted to produce smaller or larger particles by narrowing or widening the gap between the two discs. When material enters this gap, centrifugal force from the active disc flings material outwards to enable grinding between the discs.  

The throughput of finely ground product leaving the attrition mill’s grinding zone varies, though generally the coarser the material, the higher the resulting output. In addition to the gap size, the rotational speed and quantity of teeth on the rotating disc determine how fine the end-product will be. There are multiple reasons why using attrition in pharmaceutical engineering of medications works well for both active and inactive ingredients.  

Attrition Milling in the Pharmaceutical Sector

Attrition milling decreases production costs in the pharmaceutical industry while also improving ingredient stability. The process reduces particle size to make drug formulas more uniform while augmenting the medication's bioavailability to the body and solubility in water. Attrition mills often use media like ceramic or stainless steel balls to produce fine powders for capsules and tablets as well as dispersions for liquid or topical medications.

Attrition mills allow pharmaceutical manufacturers to control particle size and temperatures with precision, which is critical when working with heat-sensitive ingredients that must maintain their material properties. The attrition milling process ensures that formulations with multiple components are consistently blended, including for nanosized particles used in advanced delivery systems. Additionally, attrition mills can be used in both batch and continuous processes, allowing for research and development applications in addition to large-scale production.

Applications & Benefits of Attrition Milling

Attrition in pharmaceutical engineering processes is utilized for several applications. Capsules and tablets require that powdered ingredients are uniformly blended to ensure their consistency and accurate dosing. For topical medications, they ensure smooth textures in ointments and creams, while they can also be used for microfine powders used in inhaled medicines. While used to mass-produce medicines, attrition milling is ideal for testing formulas, along with other research and development applications.

Advantages of attrition milling of pharmaceuticals include: 

  • Drug solubility: By increasing surface area through particle size reduction, attrition milling enhances dissolution in blended medications.
  • Flexibility: Dry and wet attrition milling processes are suitable, depending on the material and formulation.
  • Nanoparticles: Supports the production of nanoparticles used in advanced drug delivery systems.
  • Particle size reduction: Attrition mills consistently produce ultrafine particles with precision to ensure accurate dosing and better bioavailability.  
  • Processing conditions: Controls shear and temperature for delicate and heat-sensitive compounds.
  • Uniformity: Evenly distributes both active and inactive ingredients.

Attrition mills play critical roles in ensuring performance and quality in today’s pharmaceutical industry.

The Rotormill: Prater’s Attrition Mill

The Rotormill made by Prater Industries is an attrition mill that provides versatile grinding at high speeds. Designed to produce finer particles, this attrition mill design can also be combined with an industrial flash drying heater as Prater’s Rotordryer®. With a centrifugal rotor for adjusting speed, operators can control particle size distribution with precision.

The Rotormill’s compact construction makes it particularly useful for a range of applications and industries, including chemical production, food processing, mineral processing, and pharmaceutical manufacturing. With its long-gap design and multiple capabilities, the Rotormill is a versatile machine that supports both batch and continuous processing. To learn more about the Rotormill and our other material handling machinery, contact the material handling experts at Prater Industries today.