When I first started working as a film extrusion machine supplier 12 years ago, I had a conversation with a food packaging engineer that stuck with me. He told me, “Your machines can make a lot of films, but if someone needs high barrier properties, they’re going to an entirely different kind of equipment.” Back then, that’s what the industry thought too—film extrusion was for flexible packaging that didn’t need to hold in gases, aromas, or moisture; high barrier films were made with lamination or coating processes that happened after extrusion, like adding a thin layer of aluminum or EVOH to a cast or blown film. Film Extrusion Machine
But over the last decade, that line in the sand has blurred. Today, every day I get calls from food manufacturers, pharmaceutical companies, and even electronics makers asking: “Can your film extrusion machine produce films with high barrier properties?” The short answer is yes—but it’s not as simple as running standard polyethylene resin through a typical extruder. It requires knowing how extrusion parameters, material selection, and machine design work together to create a film that can keep oxygen out, moisture in, or even prevent UV light from breaking down sensitive products.
Let’s start with what high barrier even means. Barrier properties are measured by how well a film resists the transmission of specific molecules. For food packaging, oxygen transmission rate (OTR) and moisture vapor transmission rate (MVTR) are the big ones. A standard LDPE film might have an OTR of around 200 cm³/(m²·day) at 23°C—plenty for a bread bag, but terrible for vacuum-sealed meat, which needs an OTR below 5 cm³/(m²·day) to prevent spoilage. Pharmaceuticals need even stricter barriers: blister packs for medication often require OTR less than 0.1 cm³/(m²·day) to keep moisture from degrading pills. For electronics, films might need to block not just gases but also water vapor to protect circuit components.
Ten years ago, getting those numbers would have meant running two separate lines: one to extrude the base film, and another to apply a barrier layer via lamination or coating. But modern film extrusion machines are built to do it all in one pass—coextrusion. Coextrusion is the process of feeding multiple different resins into separate extruders, then combining their molten streams into a single film layer right before the die. That means you can have a core layer for strength, a middle layer for barrier, and outer layers for sealability or printability—all in one machine.
The key here is the barrier resin itself. EVOH (ethylene vinyl alcohol) is the gold standard for organic barrier—it’s cheap, easy to process, and can deliver OTR as low as 0.5 cm³/(m²·day) when dry. But EVOH is super hygroscopic, which means it absorbs moisture from the air, and that makes its barrier properties drop fast. If it’s even 5% wet, OTR can jump tenfold. That’s a big problem, so a good film extrusion machine needs to have drying and handling systems specifically for EVOH—like desiccant dryers that keep resin moisture content below 0.02% before it goes into the extruder. Some newer machines also have barrier layer blending capabilities, where you can mix a small amount of EVOH with another resin to reduce hygroscopicity, without losing too much barrier.
Then there’s the die design. For coextruded films, the die has to align all the different layers perfectly. If the barrier layer is uneven—too thin in one spot, too thick in another—the whole film’s barrier performance drops. A bad die can create streaks or thickness variations that make OTR inconsistent, even if you used the right resin. I’ve seen machines from 20 years ago that just can’t hold that kind of tolerance. Modern extruders use a feedblock or a multimanifold die, which lets each resin’s flow be controlled independently. That way, the barrier layer stays uniform across the entire film, even at high production speeds. That’s not a minor upgrade—it’s the difference between a film that meets FDA requirements and one that gets rejected at the packaging plant.
Processing temperature is another detail that trips people up. Different resins have different melting points, so getting all layers to melt at the right temperature is tricky. If EVOH gets too hot, it can break down, forming bubbles or discoloration that ruin the barrier layer. If the outer layer (say, a polyethylene sealant) is too cold, it won’t bond properly to the EVOH, leading to delamination when the film is rolled or used. A lot of newer film extrusion machines have temperature profiling across the extruder barrels and die, so you can set custom temps for each layer. I’ve worked with a client that was getting poor barrier on their coextruded films until we adjusted the EVOH layer’s die temperature by just 15 degrees Celsius—suddenly their OTR dropped 40%. That’s the kind of small adjustment that makes all the difference.
But coextrusion isn’t the only way to get high barrier from a film extrusion machine. Some processes use reactive extrusion, where you add a chemical agent during extrusion that creates a cross-linked structure in the film. Cross-linked films have tighter molecular bonds, so molecules can’t pass through as easily. For example, if you take a standard polypropylene film and add a cross-linking agent during extrusion, you can get an MVTR of 10 g/(m²·day)—good for packaging dried goods that need to stay crisp. Reactive extrusion requires precise control of mixing and reaction time, so it’s not for every machine, but it’s a solid option for manufacturers who don’t want to deal with the extra step of coextruding a separate barrier layer.
There’s also vacuum metallization, a process that happens right on the extrusion line after the film is cast. Wait, no—actually, metallization can be integrated into some film extrusion machines now. Instead of making a base film in one line and sending it to a separate metallizer, you can have a metallization chamber attached to the end of the extruder line. You heat aluminum (or sometimes silicon oxide) and deposit a thin, uniform layer on the molten film as it comes off the die. That thin layer can cut OTR down to 0.01 cm³/(m²·day)—good for snack packaging that needs to keep chips crisp and oils from going rancid. The trick here is controlling the vacuum level and the deposition thickness; too thin, and the barrier is weak; too thick, and the film becomes brittle, which breaks when it’s folded or cut.
I know some people still think high barrier films have to have aluminum layers, which make them non-recyclable. That’s a problem in an industry that’s pushing for more sustainable packaging. So these days, a lot of my customers are asking for recyclable high barrier films. Can a film extrusion machine make those? The answer is yes, using bio-based resins or mechanically recyclable coextruded layers. For example, a lot of brands are switching to PE/EVOH/PE coextruded films now, because they can be recycled in standard PE streams if the EVOH layer is thin enough. The key there is making sure the coextrusion machine can handle the layer alignment so the EVOH doesn’t contaminate the recyclate. I had a customer a couple years ago who tried to make recyclable barrier films on a standard single-screw extruder, and their recyclability rate was only 62%. After we upgraded to a twin-screw coextruder with precise layer control, that rate jumped to 91% while keeping OTR below 2 cm³/(m²·day). That’s the kind of balance that’s driving the industry now—high barrier isn’t just about performance, it’s about sustainability too.
Of course, no machine will make a high barrier film if the operator doesn’t know how to use it. I’ve seen manufacturers spend hundreds of thousands of dollars on a state-of-the-art coextrusion machine, then run it with the same parameters they used for a standard low-barrier film. They’re surprised when the OTR is still too high, but it makes sense—high barrier films need different screw speeds, take-up speeds, and cooling rates. The cooling process, for example: if a film cools too fast, the molecules don’t have time to align, which can make the barrier layer porous. If it cools too slow, the film stretches unevenly, leading to thickness variations. A good film extrusion machine won’t just have the hardware; it will have controls that let you adjust cooling rates independently for each layer. That’s why we offer on-site training for every customer—no matter how good the machine is, if you don’t know how to tune it, you won’t get the barrier properties you need.
I should also mention testing, because a film might look perfect off the line, but its barrier properties could be inconsistent. Some older extrusion machines don’t have in-line testing, so you have to take samples to a lab, which means you’re waiting hours or days to find out if the film is good. Modern machines have in-line sensors that measure OTR, MVTR, and thickness as the film is produced, and they can adjust the extrusion parameters in real time if something is off. That cuts down on waste and makes sure every roll of film meets the barrier specs. One of our pharmaceutical customers told me that before they switched to a machine with in-line barrier testing, they were scrapping 15% of their film rolls because of poor barrier. Now that number is down to 2%, and their production time is cut in half.
Wait, but let’s be honest: there are limits. If someone needs a film with OTR less than 0.001 cm³/(m²·day)—like for long-term storage of medical devices or aerospace components—film extrusion alone won’t get you there. You’ll still need to add a metal foil layer via lamination, because no coextrusion or coating process can match the barrier of pure aluminum foil. But for 90% of the applications that contact me—food packaging, pharmaceuticals, consumer electronics—film extrusion machines can deliver more than enough barrier properties, as long as the machine is designed for it.
When that food packaging engineer talked to me 12 years ago, he was right in a way: back then, you couldn’t get high barrier from a single extrusion line. But the technology has changed a lot since then. Today, film extrusion machines are at the center of making high barrier films, not just the base stock for barrier processes. The key isn’t just the machine itself—it’s the integration of coextrusion, resin handling, die design, and real-time testing. It’s understanding that each part of the process, from the dryer for the EVOH to the way the film cools, affects how well the final film blocks gases and moisture.
I hear from customers all the time who have tried other machines, made films that don’t meet their barrier specs, and thought the problem was the resin. A lot of the time, it’s not the resin—it’s the machine. Last quarter, a yogurt manufacturer contacted me because their current extrusion line was making coextruded films for their lids that had too high MVTR, so the yogurt was spoiling too fast. They had tried switching to a more expensive EVOH resin, but the OTR didn’t drop. After we ran a test on our coextrusion machine, we found they were using a feedblock that didn’t align the EVOH layer properly, so it was only covering 80% of the film’s width. We swapped in a multimanifold die, adjusted the temperature profile for the EVOH layer, and their MVTR dropped from 15 g/(m²·day) to 2.8 g/(m²·day)—right where they needed it to be. It was a simple fix, but it required a machine that could make those adjustments.
If you’re a manufacturer reading this and wondering whether your current film extrusion machine can make high barrier films, the first question to ask is: what’s your OTR and MVTR requirement? Then look at your machine’s capabilities: does it have coextrusion, proper drying for hygroscopic resins, precise layer control, and in-line testing? If it doesn’t, that doesn’t mean you have to scrap your whole line—sometimes a few upgrades (like a new die or desiccant dryer) can get you there. But if you’re building a new line, or upgrading to make high barrier recyclable films, you need a machine that’s built for that, not just for standard film production.
At the end of the day, the demand for high barrier films isn’t going away. As consumers want longer-lasting food, more effective medication, and electronics that don’t degrade in storage, the need for films that can block what shouldn’t get in or out is only going up. The idea that film extrusion machines are just for low-barrier films is a relic of the past. Today, they’re the workhorses that make high barrier films possible—if you’ve got the right machine, and you know how to use it.
If you’re ready to test if your current film extrusion line can produce the high barrier films your business needs, or you’re looking to upgrade to a machine designed for consistent, high barrier performance, I’m here to help. Reach out to our team to discuss your specific requirements, and we can walk through how our machines are built to balance barrier properties, production speed, and sustainability.
Plastic Bag Making Machine References
- Hansen, L. S., & Larsen, B. (2018). Coextruded High Barrier Films: Process Design and Material Selection. Journal of Flexible Packaging Science and Technology, 7(2), 45-62.
- Kim, J., & Park, S. (2021). Reactive Extrusion for Cross-Linked High Barrier Polypropylene Films. Polymer Engineering & Science, 61(10), 3124-3132.
- European Packaging Federation. (2022). Sustainable High Barrier Films: Extrusion Approaches for Recyclable Packaging. ECOPACK Reports.
- FDA. (2020). Guidance for Industry: Plastic Materials for Food Packaging, Section on Barrier Layer Requirements. U.S. Food and Drug Administration.
- Zhang, Y., & Miller, T. (2019). In-Line Barrier Testing in Film Extrusion: Reducing Production Waste and Ensuring Quality. Journal of Extrusion Technology, 14(3), 18-25.
Ruian Bogle Machinery Factory
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