Manufacturers sometimes encounter a difficult situation: a high-strength resin provides the desired physical properties, but it does not flow easily through the processing equipment. As extrusion speed increases, die pressure rises, deposits accumulate around the die lip, and the extrudate may develop a rough surface defect known as sharkskin or melt fracture. Reducing the production rate can ease these problems, but at the cost of productivity.
This is where processing aids come in. Processing aids can provide a more practical solution by improving the way molten polymers behave during processing.
What Is a Processing Aid?
A processing aid is an additive incorporated into a polymer formulation to improve processing performance. It can help a polymer flow more smoothly through manufacturing equipment, reduce processing defects, or expand the range of workable operating conditions.
Processing aids are frequently used in extrusion processes. They may also be used in molding, compounding, blow molding, and mechanical recycling. Common application areas include film, pipe, tubing, profiles, wire and cable, fibers, and molded products.
Two Main Groups of Processing Aids
Processing aids can be divided into two main groups: lubricants and fluoropolymer-based additives (also called polymer processing aids).
1. Lubricants
Lubricants can act internally, externally, or through a combination of both mechanisms.
Internal lubricants modify interactions within the molten polymer. By reducing intermolecular friction, they make it easier for polymer chains to slip past one another instead of becoming strongly entangled. This can reduce melt viscosity, improve flow, and make the material easier to process.
External lubricants work primarily at the interface between the polymer and the processing equipment. They reduce adhesion and friction between the melt and metal surfaces, helping the polymer move through the machinery more smoothly.
The effectiveness of a lubricant depends on factors such as its compatibility with the polymer, melting behavior, and concentration. Excessive lubrication may interfere with fusion, printing, adhesion, or other downstream properties, so usage must be carefully controlled.
2. Fluoropolymer-Based Processing Aids
Fluoropolymer-based processing aids operate primarily by modifying the boundary between the polymer melt and the extrusion die.
A fluoropolymer-based processing aid is initially dispersed as particles or droplets within a host resin such as linear low-density polyethylene. During extrusion, for example, compression of the streamlines at the die entrance brings particles into contact with the die surface.
The particles then lose their individual particle characteristics. They merge to create a flowing fluoropolymer layer that develops from the die entrance toward the exit. Because this layer has relatively low surface energy, it provides a low-friction interface over which the host polymer can slip more easily.
The resulting wall slip reduces interfacial shear stress and the melt’s resistance to flow through the die. It may therefore lower apparent melt viscosity and die pressure, delay or eliminate melt fracture, and improve the surface of the extrudate.
Because polymer processing aids are typically used at very low concentrations, they generally do not materially alter the bulk properties or overall performance of the host polymer.
Where to Source Reliable Polymer Processing Aids
Selecting a reliable supplier involves more than comparing product names or prices. Manufacturers should consider whether the supplier offers appropriate grades for the target resin, processing temperature, extrusion method, and performance problem. Product consistency, technical documentation, formulation guidance, and application support are also important.
At Shine Polymer, we offer the Rheopoly® series of fluoropolymer-based processing aids for thermoplastic extrusion. Our portfolio includes grades intended for blown film, wire and cable, high-viscosity resins, and high-temperature applications. They are suitable for polyolefins such as mLLDPE, LLDPE, HDPE, LDPE, and EVA.
Conclusion
A processing aid can help manufacturers address common extrusion challenges without changing the fundamental properties of the base polymer. It can improve melt flow, lower die pressure, reduce melt fracture and die buildup, and support more stable production. If you are seeking reliable fluoropolymer-based processing aids, the Rheopoly® series from Shine Polymer offers grades designed for different extrusion applications and polymer systems.
You are welcome to contact us for more product information. You can provide details about the base resin, melt index, extrusion temperature, die design, existing additives, production rate, and observed defects so that we can recommend a suitable grade and usage.
References
- https://www.sciencedirect.com/topics/engineering/processing-aid
- https://www.tappi.org/content/enewsletters/eplace/2007/06PLA02.pdf
