Introduction to Polymer Processing Aids (PPA) and Masterbatches

1. Introduction to Polymer Processing Aids (PPA) and Masterbatches

Regarding dosage, PPA levels are typically controlled between 150 to 1500 ppm (by weight), with a maximum not exceeding 2000 ppm. To ensure uniform dispersion and full efficacy, it is generally recommended to use a masterbatch containing 2% to 3% PPA.

2. Working Principle of PPA

In current industrial practices across Europe and the Americas, fluoropolymer-containing processing aids are extensively used to improve polymer performance. When these fluoropolymer additives are mixed with the melt in an extruder, surface tension causes them to migrate toward the melt surface and adhere to the metal surfaces of the extruder, forming a lubricating film (see Figure 1).

[Figure 1: Schematic Diagram of the Working Principle of Fluoropolymer Processing Aids]

Notably, this lubricating film is dynamic: it is continuously carried away while being simultaneously replenished. To ensure the continuous formation of this lubricating film on the metal surface of the extruder head, a minimum additive level must be maintained.

3. Applications and Effects of PPA in Plastic Processing

3.1 Improvement of Plastic Extrusion Processing Performance

PPA can effectively reduce or eliminate die build-up, shortening downtime for maintenance, and is suitable for processing various plastics such as PE, PP, PEX, PA, PS, and PET. It also reduces extrusion pressure, allowing for narrower die gaps and lower operating temperatures, which saves energy. Additionally, PPA helps enhance the thermal stability of resins.

[Figure 4: Comparison between Without PPA and With PPA]

Left: Without PPA (Standard performance) | Right: With PPA (Improved clarity/efficiency)

Figure 4 shows the critical role of PPA in producing different colored films, enabling rapid transitions without prolonged equipment cleaning.

3.2 Role of PPA in Improving Extrusion Product Quality

PPA effectively reduces gel formation and ensures excellent product uniformity, significantly boosting quality—especially in PE, PP, PEX, and color masterbatch processing. Additionally, PPA eliminates melt fracture and resulting surface defects, such as sharkskin, thereby increasing the impact strength and surface gloss of the products (see Figure 5). It also maintains uniform product thickness, which is highly beneficial for multi-layer co-extrusion film processing. Furthermore, PPA excels in pigment dispersion, serving as an effective dispersant while ensuring brighter, more uniform colors and significantly faster color change speeds.

[Figure 5: Comparison of Melt Fracture (With vs. Without PPA)]

Left: With PPA (Smooth surface) | Right: Without PPA (Sharkskin/Melt fracture present)

3.3 Role of PPA in Broadening Raw Material Selection

The application of PPA makes polymers with lower melt indices (e.g., MI < 1.0) easier to process. This enables thinner films while maintaining original strength, reducing material usage and production costs. Additionally, PPA allows for an increased proportion of LLDPE in LLDPE/LDPE blends—even up to 100% LLDPE—enhancing mechanical properties. It also facilitates the effortless processing of high-viscosity resins such as metallocene polyolefins, 6C or 8C LLDPE, PEX, and HMW-HDPE.

3.4 Throughput Enhancement

PPA can increase extrusion throughput, showing significant effects when processing polymers such as PE, PP, PEX, PA, and PS.

3.5 Regulatory Compliance

4. Applicable Processing Techniques Include:

• Blown film process
• Cast film production
• Hollow blow molding
• Pipe/Tubing extrusion
• Fiber drawing
• Wire and cable extrusion
• Profile extrusion

4.1 Notes on PPA Addition Methods:

1. Ensure PPA particles are uniformly dispersed in the polymer melt; particle size should be controlled below 2 microns.
2. Typically, specialized equipment and product formulas are used to prepare PPA into a 2-3% masterbatch to facilitate uniform dispersion.
3. When mixing low MI resins with PPA masterbatch, gradually decrease the PPA concentration starting from 1000 ppm to determine the optimal content.
4. To maintain the dynamic balance of the PPA lubricating coating on the die wall, the PPA content in the processed resin must remain above a minimum limit.
5. Patience is required for the "migration time" when coating the die; this time is influenced by PPA concentration, material flow rate, equipment condition, and resin rheology.
6. The production line must be thoroughly cleaned before trialing PPA to ensure no polymer accumulation or contaminants interfere with the results.

4.2 Model Specific Applications:

5. Application of PPA in Pipe Extrusion

• Improves pipe surface quality (see Figure 6).
• Reduces apparent viscosity, shear force, and extrusion pressure (see Figures 7 and 8).
• Increases throughput: Under identical pressure conditions, PPA increases output, achieving energy savings (see Figures 9 and 10).
• Reduces/eliminates die build-up and melt fracture.
• Ensures physical and mechanical properties are maintained (confirmed by ASTM D2837 1,000-hour and ISO TR-9080 10,000-hour tests).

[Figure 7/8: Impact of PPA on Extrusion Pressure]

Y-Axis: Pressure (Bar) | X-Axis: Time (Min)

Material 1: No PPA | Material 2: 300ppm PPA (Pressure drop 6%) | Material 3: 600ppm PPA (Pressure drop 13%)

6. Advantages of PPA in PP Processing

Reducing Die Build-up and Gels

Die build-up (die drool) at the die exit degrades optical and mechanical properties. PPA prevents material stagnation at the die mouth. Furthermore, PPA reduces gels caused by equipment defects ("dead corners") or thermal degradation by maintaining a dynamic balance on the die wall, preventing the stagnation that leads to cross-linking and oxidative gels.

Managing Interferences from Other Additives

Other additives may interfere with PPA by scraping, adsorption, or competing for the die wall.

• Stabilizers: Hindered Amine Light Stabilizers (HALS) like Chimassorb® 944 show high interference, especially at high temperatures.
• Acid Salts: Anti-corrosives like Hydrotalcite (HT) or Calcium Stearate (CaSt) can interfere with die wall adsorption.
• Anti-blocking Agents: Synthetic Silicas and Talc may adsorb PPA due to high surface area.
• TiO2: Uncoated TiO2 has a higher interference due to adsorption and abrasion compared to coated varieties.