Materials Suppliers Team on PFAS-Free Solutions

As states and other government entitles move to ban so-called “forever chemicals,” material suppliers are working together to supply process aids free of polyfluoroalkyl substances (PFAS), which is a significant issue among blown film and other polyolefin-based extrusion processors that have relied on these additives to keep throughputs high.

According to Safer States, a national alliance of environmental health organizations and coalitions working to safeguard people and the planet from “toxic chemicals,” as of this writing 34 states have introduced 294 policies to protect people from these materials,” with 154 state policies adopted in 30 states. As of April 2024, Safer States adds, some 30 U.S. attorneys general have initiated litigation against the manufacturers of PFAS chemicals for contaminating water supplies and other natural resources.

The matter is critical in extrusion, where fluoropolymer-based polymer processing aids (PPA) have been used for decades to control melt fracture by lowering the surface friction of films and other extrudates as they pass through the die body and die lips, enabling processors to run at maximum throughputs. Transitioning to non-PFAS products is no small task and impacts the entire material supply chain in polyolefin extrusion. These PPAs are used by resin manufacturers as they formulate polyolefin-specific extrusion grades, masterbatch suppliers and even processors themselves.

And the issue with getting rid of “forever chemicals” has been brewing for some time. Notes James Lloyd, director, new business development of Baerlocher USA’s Special Additives Business Unit, “PFAS has been under the environmental microscope since the late 1960s — being found in water supplies, fish and fowl. In 1998, the EPA was ‘first alerted to the risks’ of human-made “forever chemicals” that build up in humans and never break down. And they have increasingly become a mainstream topic over the last several years.”

In polyolefin extrusion, PPAs are an essential material component to enable processors to keep line rates at desired levels and avoid the need to constantly clean buildup on the die lips. While additive suppliers were investigating PFAS-free formulations, some blown film machine builders began investigating die-lip coatings that would provide more slip, though, as one put it, “Ultimately this will be a material supplier solution.”

About a year ago, Baerlocher brought to market a PPA aimed at helping extrusion processors transition from per- and polyfluoroalkyl substances. Called Baerolub AID, the additive targets blown film, pipe, and wire and cable, is said to be free of PFAS and siloxanes and compatible with other additives used in film, such as anti-block or slip agents. Baerlocher says Baerolub AID PPAs deliver rapid melt fracture clearing for metallocene and Ziegler Natta linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE), equaling or surpassing clearing times of traditional PPAs containing PFAS.

“Current and evolving European Union and U.S. Federal and state regulations are forcing the plastic industry to look for new alternatives to PFAS-based processing aids,” notes Chad Harlan, Strategic Business Unit Head, Baerlocher. “To meet this need, Baerlocher USA developed Baerolub AID PPAs featuring proprietary, PFAS-free chemistry — a breakthrough that has propelled us into a leading position in the PPA space. Our new products check all the boxes for performance, cost-effectiveness, regulatory compliance and reliable supply. Upstream customers are enthusiastically adopting Baerolub AID products and blown film converters routinely request our technology.”

Because Baerolub AID PPAs are soluble in the polymer matrix, they are said to provide better haze performance than insoluble PFAS-containing PPAs and excellent control of frost line height in blown film. Moreover, the additive can reduce die buildup and extruder pressure. Because they are designed for maximum compliance with global food contact regulations, Baerolub AID PPAs are well suited for applications including polyethylene films for food packaging and resins for potable water pipe.

Baerlocher USA rolled out two grades. Dr. Robert Sherman, the company’s technical director, notes that Baerolub AID 2201 offers processors the fastest time to clear the melt fracture in metallocene LLDPE. He adds, “In certain conditions, you may wish to select Baerolub AID 2202, which provides excellent melt clearing times compared to traditional PPAs.”

Baerolub AID products are available as neat additives (pastilles, rods, granules and powders), custom blends and in masterbatch form. Baerlocher also offers customers regulatory expertise and support for lab and technical screening, blown film testing and preparation for production trials.

Resin Company Test Results

Baerlocher ran successful trials using the new PPA at its laboratory-sized blown film line in Cincinnati, Ohio, and the company notes Baerolub has also been trialed at a handful of unnamed polyolefin producers in their labs, on production-sized equipment. Efforts by Plastics Technology to engage resin producers for an on-the-record discussion of how the PFAS-free process aid performed were not successful. However, Plastics Technology purchased a study titled “Use of Non-Fluorinated Polymer Processing Aid for Polyethylene Applications,” that was posted in January 2024 by an unnamed polymer producer on the Questel website researchdisclosure.com. The 13-page presentation can be purchased for $45.

While Baerlocher would not divulge its PFAS-free formulation, the study notes that Baerolub PFAS-free PPAs are based on blends of vegetable lubricants and concludes: “(The additives) have demonstrated the ability to reduce/eliminate melt fracture, minimize die lip buildup and provide reduction in extruder torque.

“While purposely meeting the technical requirements of a PPA, the non-PFAS formulations produced by Baerlocher also satisfy a broad spectrum of criteria required for the use of said products in film applications that are destined for food contact film applications. After exhaustive screening and multiple evaluations, the Baerlocher products were the only non-PFAS PPAs that satisfied all the following criteria:

• Designed for maximum global food contact approvals and meets existing taste and odor requirements
• Environmental considerations: not noted on the “List of Substances of Very High Concern” (SVHC)
• Similar processing advantages compared to current PFAS containing PPAs at economical loadings (1,000-2,500 ppm).
• No noticeable depositions (die lip buildup or leaching/dust formation) during extrusion.
• Minimal changes in performance properties of extruded film samples, including optics (haze and gloss), printability after corona treatment and heat sealability performance
• Multiple product forms (pastilles, prills, granules and more) which can be introduced neat or formulated as a masterbatch or as a preblend mix.
• Compatibility with other conventional polyethylene additives (primary and secondary antioxidants, catalyst neutralizers, antiblock and slip additives).”

The anonymous resin supplier reported data from evaluations conducted utilizing a commercially available Ziegler Natta (ZN) ethylene-hexene LLDPE resin (melt indices of 0.918, 1.0) and a commercially available metallocene-LLPPE (m-LLDPE) resin (melt indices of 0.918, 1.0). The evaluations were conducted using three methods of introducing the PPAs into the process: fully compounded resins containing 2,000 ppm of Baerolub AID 2201; the addition of Baerolub AID 2201 as a concentrated masterbatch (5% Baerolub AID 2201 in LDPE with 4% let down ratio); and the direct addition of 100% active Baerolub AID 2201 pastilles into the base resin to achieve a 2,000 ppm concentration.

The resins utilized in the evaluations are commercially available and contained traditional blown film additive packages (primary and secondary antioxidants, catalyst neutralizer/acid scavenger). They were run on a Hosokawa Alpine monolayer blown film line utilized for evaluating the performance of the Baerolub AID 2201 against an incumbent PFAS containing PPA3. The line had a die diameter of 250-mm; a die gap of 2 mm; a 75-mm extruder with a 30:1 L/D; and dual-lip air ring; and internal bubble cooling. The screen pack configuration consisted of a 20-mesh square weave/30-150 Dutch Weave/20-mesh square weave

The line was run at a target output of 400 lbs/hr using a blowup ratio of 2.25, resulting in a film thickness of approximately 1.25 mil (31 mm). The experiments were conducted to evaluate the differences in “time-to clear” of melt fracture in the film and other processing parameters (extruder rpm, motor load, melt temperature/pressure, gauge variation).

Each evaluation followed the protocol of comparing a base resin without PPA (control) to a resin containing a fluorinated PPA and a resin containing Baerolub AID 2201.

“Time to clear” was defined in the study as when melt fracture was less than 5% around the complete circumference of the bubble. Examination of the entire bubble circumference was performed for each sample as they were collected at prescribed intervals. For consistency in determining the level of melt fracture being observed, each of the film samples were analyzed for melt fracture against a clear glass backdrop. Percentage melt fracture determination protocol was established prior to the beginning of the evaluations.

Each of the individual evaluations were typically run for two hours to track time to clear for melt fracture and to observe the stability of the processing parameters. Extended runs (12-plus hours) were also performed to determine if there were any indications of die lip buildup and to monitor for deposits either on the top of the die and/or on the film handling equipment. Experiments were also conducted with other non-PFAS PPAs that are currently being developed as potential replacements for the PFAS containing PPAs. These experiments were conducted at the recommended levels of the respective suppliers.

Critical Findings

What follows is a verbatim account of key findings published in the study:

• Melt Fracture: Figure 1 illustrates the extent of melt fracture in the extruded film vs. the run time for the different non-PFAS PPA solutions used in the evaluations along with the PFAS PPA option. It was shown that the Baerolub AID 2201 has the fastest time to clear from melt fracture among all possible non-PFAS PPA candidates.

• Extruder RPM: This showed a small increase for both the conventional process aid with fluorinated chemistry and non-PFAS Baerolub AID 2201 PPA evaluations when the additive versions were introduced. This increase in rpm was attributed to the change in coefficient of friction (lubrication/slippage) in the extruder due to the addition of the PPAs.

• Motor Load: The motor load (Figure 2) shows slightly more slippage for the Baerolub AID 2201 PPA compared to the conventional process aid.

• Melt Temperature: Similarly, tests revealed (Figure 3) a more pronounced decrease for the Baerolub AID 2201 PPA (about 7°F) compared to the conventional process aid (about 3-4°F).

• Melt Pressure: The melt pressure shows minimal increase for Baerolub AID 2201 option (Figure 4), while there is a slight increase over time for the conventional PPA.

• Gauge Variation: The gauge variation of the film shows an initial increase for the conventional PPA that dissipates over time (Figure 5), while the Baerolub AID 2201 gauge variation remains consistently low across the entire length of the evaluation. This observation is also consistent with the difference in mechanism of melt fracture elimination that is observed in the extruded film samples.

It was observed that the elimination of melt fracture for the traditional PPA occurs in bands and/or stripes (reflecting the port line positions of the dies), while the elimination of melt fracture for Baerolub AID 2201 was observed as a gradual fading of melt fracture uniformly across the film. This observed difference in clearing mechanisms is attributed to the effective dosing of Baerolub AID 2201 (2,000 ppm) being much higher than the traditional PPA solution (500 ppm), which reflects a weaker interfacial mechanism of the non-PFAS solution compared to fluorinated chemistry.

A trial was also conducted using two m-LLDPE ethylene-hexene resins (melt indices of 0.918, 1.0) in fully compounded formulations with either the Baerolub AID 2201 (2,000 ppm) or a fluoropolymer polymer processing aid (500 ppm).

In these runs, the line was started up and stabilized with the ZN ethylene-hexene resin, then transitioned after 1 hour of run time to the m-LLDPE resin with the Baerolub AID 2201. The run was continued at rate for an additional 3 hours. The “time to clear” melt fracture was around 30 minutes, and all the processing parameters continued to be stable over the entire run period. Following the three-hour run, the line was transitioned to a fully compounded m-LLDPE resin formulated with fluorinated PPA for the last hour. The “time to clear” for this formulation took approximately one hour.

Similar, to the runs with the ZN LLDPE resin, it was observed that the extruder rpm increases slightly to maintain the desired output for both the Baerolub AID 2201 and the fluoropolymer 0% containing PPA. This change in rpm was attributed to screw slippage due to the introduction of the processing aids. The motor load was also consistent with slippage for both the Baerolub AID 2201 PPA and the fluorinated PPA compounded resins.

The melt temperatures increased significantly (~ 60°F) in comparison to the startup resin as the m-LLDPE catalyzed resins have a narrower molecular weight distribution, resulting in increased shear heating. The increase in melt temperature is similar for both the Baerolub AID 2201 PPA and the fluoropolymer PPA. With respect to the ZN LLDPE startup resin, the melt pressure also shows an increase for both the Baerolub AID 2201 and the fluoropolymer PPA compounded in the m-LLDPE resin due to the increase in melt viscosity.

The gauge variation showed a considerable reduction for the m-LLDPE compounded with the Baerolub AID 2201 PPA across the run time, while it shows fluctuations even at the end of the hour run for the fluoropolymer PPA. This is consistent with the differences in the mechanisms for melt fracture elimination which is observed in the extruded film samples (as also observed for the ZN LLDPE runs conducted with PPA masterbatches). While the melt fracture elimination occurs in stripes with the fluorinated PPA, (reflecting the port line positions of the die), the resin containing the Baerolub AID 2201 had a gradual fading of melt fracture, and the reduction occurred uniformly across the circumference of the bubble.

The study concluded that:

• Within the context of the evaluations and compared to other non-PFAS containing polymer processing aids that were evaluated, the Baerolub AID 2201 shows a clear advantage for both ZN LLDPE and m-LLDPE film applications as a functional polymer process aid for blown film applications.

• The Baerolub AID 2201 demonstrated a significant improvement in “time to clear” versus both the fluoropolymer PPA (for example, 3M F5929M PPA) and the other non-PFAS PPAs evaluated in the experimental runs.

• The Baerolub AID 2201 was evaluated as a masterbatch, as a concentrate (pastilles) and as a fully compounded resin, and shows similar performance in each of the introduction methods as evidenced in the evaluations with both the ZN LLDPE and the m-LLDPE resins.

• The use of the Baerolub AID 2201 also results in faster transitions with less purging being required to remove the PPA coating from die surface versus all of the other PPAs evaluated.
• Improvements in gauge variation reduction of the bubble were also observed compared to the existing PPAs that were evaluated. This improvement was due to the different melt fracture clearing mechanisms being employed. The Baerolub AID 2201 also has a more uniform removal of the melt fracture compared to the port line elimination of melt fracture observed with the fluorinated PPA.

• Within the context of the evaluations, the Baerolub AID 2201 demonstrated the potential to replace the current fluoropolymer-containing PPAs while also satisfying a broad spectrum of criteria required for the use of said products in film applications that are destined for food contact film applications.