In the plastics industry, compounding is where performance gets engineered. Whether you're reinforcing automotive bumpers, crafting roofing membranes, or producing flame-retardant cables, it all starts with a precise blend of ingredients.
Plastic compounding recipes made of polymers, fillers, and additives are melted, kneaded, cooled, and pelletized into standardized pellets ready for further processing. But when the front end of the compounding process falters — like when dosing isn’t accurate or dust control is lacking — every step downstream suffers.
At AZO, we specialize in solving those upstream challenges with custom ingredient handling systems that deliver accuracy and safety from day one. Here’s an overview of plastic compounding, the main challenges, and how we can help you solve them.
Compounding is the process of blending a base polymer resin — such as polyethylene (PE) or polypropylene (PP) — with various additives to engineer materials for specific applications. Additives can include colorants for appearance, stabilizers for heat or UV resistance, flame retardants, and impact modifiers. Fillers and reinforcements like fiberglass are used to adjust cost, stiffness, or strength.
This mixture is typically processed through an extruder, melted, and pelletized for downstream use. Advantages of compounding include tailored performance, aesthetic customization, material efficiency, and support for sustainable practices through recycled content.
At the heart of compounding is the extruder: a heated screw system that melts and homogenizes ingredients. Once compounded, material is cooled and cut into uniform pellets, often about the size of a small pill, which are then shipped to another facility for final molding, or extrusion.
AZO’s systems come into play before the extruder ever starts spinning. We handle everything from bulk bag unloading and microdosing to pneumatic conveying and explosion mitigation, ensuring that every ingredient gets where it needs to be, safely and accurately.
For some manufacturers, it’s more economical to purchase pre-compounded pellets. But there’s growing interest in bringing compounding in-house to gain more control over product quality and cost. When done right, in-house compounding lets you:
This decision comes with serious design considerations, especially when it comes to handling explosive materials or managing ingredient variability.
Explosion hazards are the number one compounding challenge. Some process aids used in compounding, like those that help materials flow more smoothly through the extruder, are highly flammable. These additives may have high Kst values, meaning they can ignite under the right conditions. To mitigate this, AZO calibrates production equipment to ensure that ingredient flow doesn’t create combustible conditions. All our equipment meets NFPA 660 standards.
Dosing accuracy isn’t one-size-fits-all. For applications like commercial decking, tolerances can be broad. But when you're manufacturing IV bags or syringes, every gram counts. That’s why AZO begins by understanding your required accuracy in order to engineer systems to match. We replace manual ingredient dosing with automation that ensures precision.
For example, we’ve seen scenarios where a manufacturer was losing up to 10% of their product as dust due to open dumping. By switching to AZO’s automated, dust-tight systems, they gained tighter control, minimized loss, and were able to account for every ingredient. Our gravimetric and loss-in-weight solutions provide precise dosing and full recipe traceability.
Resins, fillers, and additives all behave differently. Some clump and others flood; some resist flow entirely. These differences affect dosing rates, blending homogeneity, and even safety. AZO conducts lab tests to validate material behavior and engineer solutions that account for variability before they go live in your facility. Because compounding can sometimes include up to 10 ingredients (major and minor), each ingredient needs to be properly assessed to make sure it plays well with your production line.
Color changeovers or new recipes can introduce cross-contamination if lines aren’t cleaned properly. AZO designs systems that promote rapid disassembly and clean-out. For example, dosing screws are rail-mounted for easy removal and can be self-wiped between batches.
One trick manufacturers use is running clear plastics before other colors like black, but you’ll typically still need to run a clean out for four to five loads with no color before starting a new product. Having equipment that’s easy to clean is important to minimize that downtime.
Whether you’re starting from scratch or optimizing an existing system, AZO engineers are here to help you design for success. For compounding specifically, we recommend:
For customers using pre-compounded pellets, our MIXOMAT in-line blending system lets you mix different pellets just before extrusion, reducing the need for multiple feeders and ensuring consistent feed quality. In the field, the MIXOMAT is used to make food wrappers, airplane seat plastics, medical bags, commercial 3-ply laminate roofing, car bumpers, and more.
With recipe management software and real-time data capture, our systems provide the level of accountability and precision today’s manufacturers require. You’ll know exactly what went into each batch and where it went.
AZO systems are designed to reduce dust at every transfer point. That includes sealed connections, explosion venting, dust-tight transitions, and centralized dust collection, which are all NFPA 660 ready.
Once compounded, AZO can convey pellets pneumatically to any vessel of your choice like bulk bags, silos, or directly into railcars, in order to streamline your packaging and distribution process.
Whether you're navigating combustible dust risks, struggling with dosing consistency, or preparing to bring compounding in-house, AZO has the engineering expertise to help you build a smarter system. From material testing to automation integration, we design solutions that deliver safety, accuracy, and performance right from the start.
Let’s talk about your compounding goals. Contact us today.