How a Toll Processor Can Optimize Application & Processing of Polymers
KT Brickman, Jun 10, 2020 8:00:00 AM
It’s no exaggeration to say most Americans have interacted with a polymer-containing product within the last five minutes.
Polymers are a constant of everyday life. In fact, it’s hard to imagine doing much without them. They make up constituents of our water bottles, shopping bags, electronics, athletic clothing, cosmetics, pharmaceuticals, paints and coatings, and toys.
High-performance polymers have become essential materials for technical industries including aerospace, automotive, architectural, and high-tech medical devices.
Polymers’ mechanical properties range widely, too. Some, like rubber and polyester, bend and stretch. Others are hard and solid, like epoxies and glass.
When people think of polymers, they often think of plastics. But the definition of polymer is broader than that. Strictly speaking, a polymer is a substance made of many smaller molecules linked together to form larger ones.
Wood, wool, and even protein are natural, or organic, polymers. Plastics, nylon, and epoxies are synthetic, or inorganic, polymers.
In short, all plastics are polymers, but not all polymers are plastic.
Key Polymer Processing Techniques
Polymer processing methods can achieve widely varying target specifications, from adding filler materials to micronization, depending on the material’s intended end use and its physical characteristics. Some of the most common polymer processing methods include:
- Jet Milling — Micronizing with high-velocity air to perform autogenous (self) milling in a fluid bed. Often, an adjustable internal classifier is used to separate particles of the desired particle size and shape. Jet mills may include hot gas, ceramic lined, and stainless steel varieties.
- Extruding — Extrusion is a specialty melt-blending technology that involves applying pressure and elevated temperatures to the polymer, often adding a less-expensive filler. Extrusion can help control costs without sacrificing important characteristics, preserving the polymer’s performance in the end use.
- Cryogenic Milling — Some softer, more flexible polymers can be frozen for milling, so they become more brittle and easier to break down in the mill.
- Screening — After milling, it can be necessary to remove unwanted larger or smaller particles from the bulk material by passing it over a screen.
- Classifying — Some mills have classifiers built into the chamber; some don’t. Dispersing the finely milled polymer in air and using an adjustable classifier to control the final particle size can remove oversize or undersize particles.
- Blending — Powdered polymers can be dry or wet blended to create a unique product that is then further processed by extruding, dry milling, or wet milling.
- Wet Milling — Very fine particle sizes are possible by dispersing a powdered polymer in a liquid carrier and/or mixing with multiple ingredients to create a slurry, at ambient conditions, heated or cooled, then media milled to the desired size.
In many cases, multiple processing methods are applied in a series of steps to achieve a specific desired outcome. For example, a polymer may need to be extruded to blend two or more materials together, and then the outcome may need to be jet milled to produce a fine polymer powder.
How Do You Know Your Polymer? Start with an SDS
Before a toll manufacturer’s team determines the appropriate processing steps and equipment, they need to examine, evaluate, and measure initial material characteristics. Before any work can be done, a Global Harmonized System (GHS) compliant Safety Data Sheet (SDS) is needed. From there, the technical team documents every detail, including:
- Initial particle size (granular, powder, or larger pieces)
- Bulk density
- Moisture content
- Combustibility (explosivity data is needed)
- Allergen information
- And more
If the team or the customer has successfully processed the same material in the past, they’ll consult previous process details from that experience. If the project has the same or similar goal, documentation of previous processes can provide an excellent starting point. If not, the team can at least glean material and technical insights from the data.
Two types of information are especially valuable to toll processing teams when starting a project:
- Melt Temperature — Extruding involves melting polymer(s) to incorporate a filler, which itself does not melt. Knowing the melt points of all polymers involved adds precision to the process from the start.
- Glass Transition Temperature — In order to cryogenically mill a polymer, it needs to be reduced in temperature enough to make it brittle. In other words, it needs to be brought to its transition temperature.
If a reference sample is available of the finished product, technical experts will study it using particle size analysis equipment such as a MICROTRAC MRB, Malvern Mastersizer 3000, HORIBA, or Alpine Air Jet Sieve. A clear look at particle size, ranges, and morphology can tell the team a lot. With enough data, a process trial could even be bypassed, moving the project straight to production-scale processing equipment, and saving time and money.
Trust Polymer Toll Processing Experts to Ask the Right Questions
Material scientists and engineers choose the most efficient processing technology based on their evaluation of material properties and your project’s particle size goals. Asking questions about the application, use, and characteristics of the final product helps the team ensure the polymer end product achieves the project objectives.
Based on investigation, reference sample data, and customer collaboration, the team looks for answers to relevant questions, including:
- Do materials require particle size reduction, blending, or both?
- Is a specific polymer particle shape or surface characteristic needed, or is size reduction the sole focus?
- Is a filler needed? At what percentage?
- Can existing equipment and processes achieve the specifications, or is a new piece of equipment needed?
Polymers’ wide range of material characteristics can make for an equally wide range of toll processing challenges, and the processes needed to achieve target specifications can range from straightforward and simple to multi-step and quite complex.
Achieving a challenging particle size or shape — especially in combination with challenging material characteristics — can require multiple processes. For example, a technical team might determine that a rubbery polymer needs to go through a cryogenic pre-grinding step before jet milling to achieve the intended particle size.
While most customers approach their tolling partner with product formulations already established, at least in bench trials, a technical team with significant polymer experience can perform larger-scale trials to ensure your formulation is ready to scale up for production and establish process protocols for production runs. They can also design experiments to help define and control process changes needed to respond to changing formulations.
Why Choose a Toll Processor for Polymer Applications?
One major advantage of working with an experienced polymers toll processor is getting access to a wide range of processing equipment. That equipment range enables you to investigate a broader range of polymer options, because you can run product trials on so many different equipment types — run by experts — without having to invest in your own machines, installation, or specialized personnel.
What types of equipment trials can a toll processor perform? It’s important to ask, but you should expect:
Feasibility testing: A feasibility station is the smallest trial available, for early initial tests on a polymer material to evaluate how it behaves during processing.
Pilot trials: A pilot-sized unit can trial small amounts of product (100 - 200 kg minimum) to cost-effectively determine larger-scale production rates. A truckload of material isn’t required to confidently nail down processing steps moving forward.
Access to the right trial equipment makes it easier to determine the best production approach. If a jet milling trial doesn’t hit the mark, the team can try a mechanical mill with nitrogen, for instance. This maximizes efficiency and creates a shorter path to your polymer’s final production.
Another efficiency value-add is a toll processor’s ability to perform multiple steps at one location — e.g., extruding and adding filler and then milling the extruded polymer to the target particle size range. When you can do it all at the same toll processor, you save time and control quality.
Pharmaceutical-grade polymers are used within cGMP toll processing, and that requires working with a toll processor that can meet a uniquely stringent set of quality standards, demonstrated by the certifications required for processors of food and pharmaceuticals. If your polymer application involves cGMP regulations, be certain your toll processor is properly accredited.
Polymers are just one large group of many materials, natural and synthetic, that demand specialized expertise from a toll processor to precisely and safely mill, blend, compound, pelletize, and much more. You can learn more about the most important terms used to describe material characteristics and specifications, measurements, equipment, industry certifications, and more when you download our Glossary of Particle Processing Terms. Just click the link below to download your copy today.