Toll Manufacturing Minute with CPS: Particle Size Reduction

Welcome to the Toll Processing Minute with Custom Processing Services! Each month, we sit down with an in-house expert to explore various facets of toll processing—from best practices and processes to industry trends and current headlines. Join us for brief yet insightful conversations with Custom Processing Services team members, where we dive into the expertise only seasoned toll processors can offer.

In this episode, we’re speaking with Willow Slusser about the intricacies of particle size reduction and the technologies that make it possible.

Watch our debut episode now:

Jen Lepore: So let's get started. I'm Jen Lepore, Marketing Team Coordinator at Custom Processing Services, and today I'll be talking with Willow Slusser, one of our business development managers, about particle size reduction, and a recent webinar she just presented on this topic.

So, hello, Willow.

Willow Slusser: Hi. Nice to be here.

Jen: So, a couple of questions to get started. Since so many industries rely on particle size reduction, why is this process so important?

Willow: It's so important because you are adding value to that material. You are bringing in a raw material, and you are transforming it into something completely different. You can engineer it to exactly what you need it to be, whether it matches a specific specification, a specific property that you need the material to have, or just the functionality in general.

Jen: Now, what does a toll processor need to know to align the processes with the raw material and the project's end goal?

Willow: Sure, it's super important to understand the characteristics of the raw material. Understanding if it's heat-sensitive, moisture-sensitive, or friable. You take all those into consideration when you're picking out the mill that you need. Depending on the particle size and your end goal, this guides you to choose the equipment that you need.

Jen: So how is the target particle size determined?

Willow: It really depends on just the functionality that the end user is looking for. Whether it be nano-sized materials for pharmaceutical applications because the particle needs to be a certain size to be able to get through a certain barrier in the body, or in the agricultural industry, where the particle size needs to be absorbed into the plant. Or, if it's a pesticide, what does it need to be in order to be absorbed into the insect, fungus, or whatever it's attacking?

Jen: Awesome. Now, what types of technologies are used to reduce the particles?

Willow: We have quite a few. Our business started with jet milling, and obviously, we love jet milling here. That's particle-on-particle collision using gases as the force. We also have a plethora of mechanical mills focused on all different particle sizes. We have coarse crushing for starting out with big boulders of material, or we have universal mills that have a large range of particle sizes they can achieve because they have interchangeable parts. We also have wet milling that gets down to nano-sized particles. You can get down to an average of 50 nanometers, depending on the raw material and if it allows you to get there.

Jen: Wow. So what factors would you say go into a toll processor's choice in the grinding and milling technologies?

Willow: A lot of that is based on what the end user is looking for. If they're looking for a nano-sized particle, you're definitely going to be looking at wet milling. If we're looking at a coarser-sized particle, we might use our coarse system set up with different mesh sizes that we're targeting. If it's an 80 mesh, it might go through our coarse system. It all depends on the starting particle size too, because that might play into how many steps are needed to get down to the particle size you're looking for. So if it's coming in as big boulders and we need it down to minus 325 mesh, we might have to go through several different steps.

Jen: So that kind of leads into the next question. How does a toll processor influence the particle size and shape, and why is it important?

Willow: You're influencing the particle size and shape by the type of milling equipment that you're choosing. If you start milling and suddenly have a ton of fines, we can shape that particle size distribution by using air classification or sieving in general to cut off a certain portion of that distribution. So, you can really pick and choose how narrow or wide your distribution is.

Jen: So how would you say the material impacts the processes?

Willow: The material really impacts it because, if you're looking at how friable a material is, and it's not friable at all, you might need to go to cryo milling, and that can only be done on specific mills. So it guides you as to where you need to go.

Jen: Speaking of cryo milling, can you explain a little bit about what cryo milling is?

Willow: Yeah, sure. It's utilizing nitrogen in the process. It could be just gas, but it could also be liquid. Gas might be enough to get it chilled and able to break apart more easily. But sometimes you need to submerge your raw material in nitrogen before it goes into the mill or have it run into the mill itself. That way, it creates a real cold atmosphere in there, making the material more friable to be broken down. We use that a lot in plastics as well. We recently ran PVOH, which comes to mind here. But yes, depending on the molecular weight of the plastics, it will determine whether you need cryo milling or not.

Jen: That's interesting. So would you say certain material characteristics warrant special handling, like combustibles and abrasives? How do toll processors approach these types of needs?

Willow: At CPS, we actually have a whole safety process. When we first get an inquiry or a new project, we evaluate the SDS of the raw material first before we do anything, because that really helps figure out what you need to do. If it has any type of combustible dust, we'll evaluate what's called the Kst, which is the rate at which an explosion could happen, the Pmax, which is the maximum pressure that would be exerted, and the MIE, which is the minimum ignition energy. Those three values really come into play when evaluating combustibility. We have a bunch of different calculations that we do to figure out if we can run it on this station with this collector, and if it is reinforced enough to handle a deflagration incident. For abrasiveness, we have different types of wheels, for example, that go into our jet mills. The classifier wheels are made out of different materials and are interchangeable, so you can switch them out if needed. There are specific wheels for abrasion resistance. The same goes for our wet mills. Different chambers and different agitators are made out of different materials, so you can pick and choose which material can handle it. For example, with solvents, different solvents don't do well with specific materials, so the interchangeability allows us to adjust to the raw materials.

Jen: So obviously, safety is a big portion of what we do here, right?

Willow: Absolutely, yes. That's the first part of our process. We always ask for the SDS and then do our safety evaluation. During that, you also learn a lot about the material and what equipment you can and cannot run it on.

Jen: Thank you so much, Willow, for all of your insight. And thank you, everyone, for watching. If you have any questions, feel free to reach out to myself or to Willow. She's on LinkedIn as well. Please visit our website and subscribe to our blogs, where you'll be able to get early access to our next Toll Processing Minute episodes.