Mastering Powder Blending: 4 Keys to Selecting the Right Toll Processor

Today, consumers want more variety from manufacturers than ever before. To meet this demand, manufacturers are rapidly adding new versions or “recipes” to their portfolios, especially in powder blending.

Blending is the pivotal process where “ingredients” transition into “products.” While it may seem straightforward, powder blending, stands out as a complex and essential step in product development. Achieving a uniform mix of material is no easy feat, and it’s often crucial for a product’s success. Merely being “well blended” isn’t sufficient; it must be executed flawlessly every time.

Powder blending, or mixing, is prevalent across various industries, including food, pharmaceuticals, metals, minerals, chemicals, and plastics. From the initial feasibility phase to production, precise powder blending expertise can effectively address numerous challenges and refine the manufacturing process. Consequently, there’s a notable demand for companies proficient in blending powder ingredients.

For many manufacturers juggling multiple product lines, relying on expert toll processors for blending is vital to uphold hygiene and production standards. But, not all toll processors have powder blending services. Of those that do, a handful rise to the top in terms of truly understanding and applying powder blending principles. Look for expertise in these four focus areas to select the right toll processing partner:

1. Comprehensive knowledge of powder blending characteristics

Many products rely on the correct mixing of powder and/or granular materials. Ideal dry powder blending depends on a thorough understanding of the materials' characteristics and properties, as well as their interactions during the blending process.

For instance, particles of similar sizes mix easily, so you want to achieve uniformity, if possible. On the challenging side, some fine powders can become electrostatically charged, which you want to minimize. Some additional characteristics include powder density, moisture content, and lubricity.

When evaluating a blended product, individual characteristics are grouped by features and placed in one of the following three categories:

• Flowability is crucial in processing, and it depends on both the materials and the blending equipment. For smooth operations, powders must flow freely from storage to processing. Interparticle forces, like van der Waals and electrostatic forces, significantly impact flow behavior, particularly cohesive properties that cause powders to clump together. Even slight moisture can disrupt flow, emphasizing the importance of closely monitoring humidity levels.
  
  
• Homogeneity goes beyond mere blending. For instance, in pharmaceuticals, where micronized powders (less than 10 microns) are crucial for faster drug absorption, ensuring uniform distribution of the active pharmaceutical ingredient (API) and excipients is essential.
  
  Differences in particle sizes between the API and excipients can lead to ingredient separation. Additionally, stickier excipients pose challenges in blending. 

• Sampling is the sole method for analyzing blends. Different methods like thief sampling and stream sampling aim to provide representative samples. In powder blends, variations often stem from particle size distribution. As mix quality diminishes, sampling issues typically escalate. 

Toll powder blending requires a deep understanding of individual particle characteristics to ensure the mix’s quality standard is achieved. These are features the right toll processor should document for you.

2. Deep understanding of and access to specialized equipment

In powder blending, it's crucial to have specialized equipment. There are four primary types of blenders essential for effective powder mixing:

• Fixed-shell blenders (ribbon, paddle, screw mixers) have an internal rotating device that provides a continuous shearing force on the particles, breaking up agglomerated powder particles as they slowly and gently mix powders.
  
  Within a ribbon blender, a double-helix agitator performs two tasks: the outer blade moves material to the center of a trough; the inner blades move material to the outside of a trough. Paddle blenders, a slightly different design, is best for small batches and friable materials.

• Rotating-shell blenders (twin-shell or “V,” drum, double cone), are generally more gentle than fixed-shell blenders. Free-flowing particles mix as they slide and tumble together -- much like a concrete mixer on a truck.
  
  
• High shear blenders handle sticky, cohesive powders well, forcing particles to fold together. Proper management is required so particle degradation and heat build-up doesn’t occur in the mixture.
  
  
• Plow-style blenders, a type of high shear mixer, are used when particle size reduction and granules are needed.

Determining the appropriate blender size for toll powder blending primarily relies on the powder’s weight and flow properties. The weight aids in estimating the necessary working capacity, while the flow characteristics dictate the type of blender required to accommodate the product. Blender size is usually determined by volume, while powders are measured by density. 

A particle’s characteristics influence the selection of a blender. Ensuring a consistent blend depends on factors such as the blender’s speed, fill level, flow rate, and mixing duration. It’s not merely a matter of blending for a prolonged period, as this can lead to ingredient separation in certain instances. In fact, mixing time needs to be adjusted for each formulation to achieve blend uniformity.

3. demonstrated capabilities in powder blending process optimization

When determining batch size for toll processing, bigger isn’t always the best. With powder blending, large volumes or extended mixing times can compromise homogeneity. Partner with a trusted powder blending company for tailored solutions and optimal results. 

What you’re really looking for in a powder blending company is the ability to process a range of batch sizes with a focus on minimizing downtime and meeting scheduling needs. Flexibility offers agility, enabling quick adaptation – whether for short runs or multiple batches – thus outpacing competitors. 

This raises the topic of manufacturing processes, particularly batch and continuous processing. 

• In traditional batch processing, product components are assembled sequentially. This process may involve multiple equipment stages, with each batch completed before the next begins processing. 
  
  
• In continuous processing, a product goes from base ingredients to final product without needing to stop production; so no equipment shut down and no downtime. It’s time-efficient, reduces energy use, increases productivity, reduces waste and, lowers the risk of human error since fewer people are involved..

Some products require batch processing because of their composition or formula, and some are best for continuous processing. The best powder blending toll processors are flexible enough to handle both techniques.

4. consistent and thorough quality assurance protocols

Toll processors prioritize cleanliness. When evaluating various options, examine their quality assurance and control procedures, as well as their track record.

Powder blending is especially challenging, with equipment requiring extensive cleaning to prevent cross contamination between products. Cleaning protocols need to be in place to prevent contamination.

Consider creating an audit that helps you review quality failures, compliance issues, and the strengths and weaknesses of the toll processor. It’s essential to note that a reputable toll processor should routinely trace products from arrival to departure as a standard practice.

Also, industry certifications shouldn't be overlooked. Multiple certifications attained by a powder blending company indicate a high standard of cleanliness and minimal risk of cross-contamination. 

Your powder blending partner acts as the ultimate safeguard for your product before it reaches customers. These four considerations set you on a path to success, which you can supplement with insightful terms and definitions found in our Particle Technology Glossary.