{"id":451,"date":"2026-09-23T10:04:55","date_gmt":"2026-09-23T02:04:55","guid":{"rendered":"http:\/\/www.drinkforlifes.com\/blog\/?p=451"},"modified":"2026-09-23T10:04:55","modified_gmt":"2026-09-23T02:04:55","slug":"what-is-the-gas-permeability-of-plastic-film-47b4-721469","status":"publish","type":"post","link":"http:\/\/www.drinkforlifes.com\/blog\/2026\/09\/23\/what-is-the-gas-permeability-of-plastic-film-47b4-721469\/","title":{"rendered":"What is the gas permeability of plastic film?"},"content":{"rendered":"

Hey everyone, thanks for swinging by my little corner of the internet\u2014when I\u2019m not geeking out over plastic films at work, I\u2019m here to break down stuff I get asked nonstop by clients, new and old. Today\u2019s topic is one that comes up all the time: gas permeability of plastic film. If you\u2019re here because you\u2019re looking for films for food packaging, medical supplies, or even industrial stuff, this is the lowdown you actually need, not the boring textbook jargon I used to sit through in college. Let\u2019s dive in. Plastic Film<\/a><\/p>\n

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First, let\u2019s keep it real\u2014gas permeability isn\u2019t just a random tech term. It\u2019s basically how easily gases (think oxygen, carbon dioxide, nitrogen, even water vapor) pass through a plastic film. For most folks, this matters way more than you\u2019d guess. Like, have you ever grabbed a bag of chips that\u2019s still crisp a month later? Or a bottle of wine that tastes the same as the day you bought it? Or even a batch of fresh berries that doesn\u2019t get moldy in three days? That\u2019s all thanks to a film\u2019s permeability. Mess that up, and you\u2019ve got chips that go stale, medicine that loses its effectiveness, or produce that rots way too fast. And as someone who\u2019s been supplying plastic films for over 10 years, I can tell you\u2014this is one of the first questions I ask any new client before we even talk about pricing.<\/p>\n

Let\u2019s start with the basics that everyone gets confused about, because I\u2019ve had so many clients mix these two up: permeability vs. permeance vs. perm-selectivity. Yeah, it\u2019s a mouthful, but let\u2019s keep it simple. Permeability is the inherent property of the plastic material itself\u2014like how \u201cporous\u201d it is to gases, no matter the thickness. Permeance is permeability divided by the film\u2019s thickness, right? So if you have a super thin film and a thick film made of the same plastic, the thick one will have lower permeance because the gas has to travel farther. Then there\u2019s perm-selectivity\u2014this is the cool part, where a film lets one gas through way easier than another. For example, a lot of food packaging films are selective to carbon dioxide, so CO2 (which helps keep food fresh) escapes slowly, but oxygen (which makes food go bad) is blocked. That\u2019s the magic combo for snacks like pretzels or beef jerky.<\/p>\n

Now, what actually makes a film permeable? I get this question all the time\u2014why does one plastic let oxygen through, and another stops it cold? It comes down to how the plastic is structured, and it\u2019s not as random as you might think. First, the polymer type is huge. Like, think of two common plastics we sell a ton: LDPE (low-density polyethylene) and EVOH (ethylene vinyl alcohol). LDPE is super flexible, used for things like grocery bags or bread wrappers\u2014gas can slip through its loose polymer chains easy, so it\u2019s high permeability. EVOH, on the other hand, has tighter, more ordered polymer chains that pack really close together, so gases can\u2019t move through as well. That\u2019s why EVOH is the go-to for films that need to block oxygen, like for meat packaging or pharmaceutical blister packs.<\/p>\n

Wait, but there\u2019s a catch with EVOH\u2014its permeability changes a lot with moisture, right? If it gets wet, the polymer chains absorb water, which makes them loosen up, so oxygen can pass through way easier. That\u2019s a thing we always warn clients about\u2014you can\u2019t use straight EVOH for frozen food, because frost would mess with its barrier. We usually laminate it with LDPE or another moisture-resistant plastic to fix that problem. That\u2019s just one example of how even the most \u201cbarrier-heavy\u201d films have tradeoffs, and knowing those is what makes all the difference for a good packaging solution.<\/p>\n

Next up, thickness. Like I mentioned earlier, thicker films have lower permeance, but permeability stays the same because it\u2019s a material property. But here\u2019s the thing\u2014you don\u2019t always want a thicker film. Thicker stuff is more expensive, stiffer, and not great if you need flexibility. Like, if you\u2019re making a bag for frozen veggies, you need a little thickness to hold up in the freezer, but you don\u2019t want so much that it\u2019s bulky and hard to seal. So it\u2019s all about balancing thickness with the gas barrier you need. For example, a 1 mil (thousandth of an inch) LDPE film has an oxygen permeability of around 200 cc\/(m\u00b2\u00b7day\u00b7atm) at 23\u00b0C, while a 2 mil LDPE is half that, at ~100. But an 8 mil EVOH film is like 0.1 cc\/(m\u00b2\u00b7day\u00b7atm)\u2014that\u2019s basically airtight, which is why it\u2019s used for long shelf-life foods.<\/p>\n

Then there\u2019s processing\u2014how we make the film matters a ton too. Two films made of the exact same polymer can have totally different permeability if they\u2019re processed differently. Like, if you stretch a film during manufacturing (we call that orientation), you can align the polymer chains to be more ordered, which makes the barrier better. Biaxially oriented polypropylene (BOPP) is a perfect example\u2014regular PP is pretty permeable, but when you stretch it in two directions, the chains line up tight, so it\u2019s way better at blocking oxygen and water vapor. We use BOPP for a lot of snack packaging, like candy bars or granola bars, because it\u2019s lightweight, cheap, and has a solid barrier. Also, additives\u2014stuff like plasticizers or fillers can change permeability. Plasticizers make the polymer chains more flexible, which lets gases slip through easier, while fillers like clay can act like little roadblocks, making the barrier better. That\u2019s why we\u2019re careful with additives\u2014too much of one and you ruin the barrier you worked hard to get.<\/p>\n

Wait, let\u2019s talk about real-world applications, because that\u2019s what everyone cares about. I\u2019ve seen so many clients buy a film that looks good on paper, but fails in actual use because they didn\u2019t match the permeability to their product. Let\u2019s break down a few common uses:<\/p>\n

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  1. \n

    Fresh produce: Berries, apples, leafy greens. These are living things, right? They breathe, so they take in oxygen and release carbon dioxide. If you use a film that\u2019s too impermeable, the CO2 builds up inside the bag, and the produce rots. If it\u2019s too permeable, the oxygen escapes too fast, and they wilt. That\u2019s why we use perforated films or films tuned to let just the right amount of gases pass\u2014we call that \u201crespiratory-modified packaging.\u201d For example, a bag for strawberries needs a little higher permeability than a bag for apples, because strawberries breathe faster. I remember a client last year who was using a regular LDPE bag for their organic spinach, and it was going bad in 2 days. We switched them to a custom-perforated PE film with permeability calibrated for leafy greens, and suddenly their spinach was lasting 5 days in the store\u2014no more waste, no more returns. That\u2019s the stuff that makes my job worth it.<\/p>\n<\/li>\n

  2. \n

    Packaged food: Chips, nuts, jerky. These products don\u2019t breathe, so they need to block oxygen to prevent staleness and spoilage. That\u2019s why we use films with high oxygen barrier\u2014usually laminated films with EVOH or PA (polyamide, also called nylon). For example, a potato chip bag is usually a 3-layer film: PE (inside, seals to the chip), aluminum foil (blocks light and gases), and PET (outside, protects the foil). The foil makes it almost totally impermeable, so chips stay crispy for months. But if foil is too expensive or you need a flexible film, we use high-barrier EVOH laminates that don\u2019t have foil\u2014those are great for snacks that need to avoid aluminum for dietary reasons.<\/p>\n<\/li>\n

  3. \n

    Medical\/pharmaceutical stuff: This is where permeability is non-negotiable, almost. For things like blister packs for pills, you need a film that blocks oxygen and moisture totally, because even a tiny bit of moisture can make pills break down. For sterile wound dressings, you need a film that lets water vapor (sweat) pass through, but blocks bacteria and oxygen, so the wound stays moist and doesn\u2019t get infected. I can\u2019t stress enough how critical this is in medical use\u2014one wrong film and you\u2019ve got a product that\u2019s unsafe, which is why we only work with films that meet FDA and ISO standards for medical applications.<\/p>\n<\/li>\n

  4. \n

    Industrial uses: Things like shrink wrap for pallets, or films for protecting electronic parts. For shrink wrap, you need a film that\u2019s permeable enough to let air escape when you heat it, so it tightens around the pallet evenly. For electronic parts, you need a film that blocks moisture, because even a tiny bit of humidity can ruin circuit boards. I\u2019ve had a tech client who was using the wrong film for their circuit board packaging, and they had 10% of parts get damaged during shipping because the film let moisture in. We switched them to a moisture-barrier polyolefin film, and that problem went away.<\/p>\n<\/li>\n<\/ol>\n

    Now, let\u2019s get into how we test permeability\u2014this is another big one clients ask about, because numbers matter. There are standard tests, right? For oxygen permeability, we use ASTM D3985, which measures how much oxygen passes through a film over a certain time, area, and pressure. For water vapor, it\u2019s ASTM E96. The units are usually cc\/(m\u00b2\u00b7day\u00b7atm) for oxygen, or g\/(m\u00b2\u00b7day) for water vapor. When a client comes to me with a specific need, I first ask: what product are you packaging? What\u2019s the shelf life you need? What are the storage conditions (temperature, humidity)? Then I run tests on sample films to match exactly what they need. It\u2019s not one-size-fits-all, that\u2019s for sure.<\/p>\n

    Here\u2019s some common myths I hear all the time, let\u2019s bust those. First myth: \u201cThicker film is always better barrier.\u201d No, like I said earlier\u2014if you double the thickness, you halve permeance, but sometimes you can get a better barrier by switching to a different polymer. For example, 2 mil EVOH is way better barrier than 10 mil LDPE, and way thinner and more flexible. So thickness isn\u2019t the only factor. Second myth: \u201cAll barrier films are the same.\u201d Nope\u2014EVOH, PA, PVDC, aluminum foil, each has their own pros and cons. EVOH is great for oxygen, bad for moisture; PVDC is moisture-resistant but has some environmental concerns; foil is super barrier but can be heavy and not recyclable. We work with clients to pick the best one for their needs, not just the most expensive. Third myth: \u201cPermeability is only about gases.\u201d Water vapor permeability is a huge part of it too\u2014sometimes called moisture vapor transmission rate (MVTR). For example, a bag for bread needs to let a little moisture escape so it doesn\u2019t get soggy, but block oxygen so it doesn\u2019t go stale. That\u2019s balancing gas and water vapor permeability, which is a fine line.<\/p>\n

    As a supplier, I get that a lot of clients don\u2019t have a background in polymer science, so it\u2019s my job to walk through all this without making them feel lost. I don\u2019t just sell a film and move on\u2014we work with them from the start, testing samples, adjusting formulations, making sure the film fits their exact use case. I\u2019ve been doing this long enough to know that a good film isn\u2019t just about the specs on a sheet\u2014it\u2019s about solving their specific problem. Last year, a craft brewery came to me looking for a film to package their canned craft beer. They didn\u2019t want aluminum cans because they were heavy, and they needed the beer to stay fresh for 6 months. We worked together to create a custom laminated film with a high-barrier EVOH layer, and we did tests to make sure it blocked oxygen enough, and also let just a tiny bit of CO2 escape so the beer didn\u2019t go fizzy in the wrong way. It took a couple of rounds of samples, but it worked, and they\u2019ve been a regular client ever since. That\u2019s the kind of relationship I value more than anything.<\/p>\n

    Now, if you\u2019re here because you\u2019re looking for a plastic film for your product\u2014whether it\u2019s food, medical, industrial, whatever\u2014here\u2019s what you should think about before reaching out. First, know your end goal: is it to keep oxygen out? Moisture in? Let gases escape? How long does your product need to last? What\u2019s the storage environment (hot, cold, humid, dry)? How important is flexibility vs. strength? Once you have those answers, that\u2019s half the battle. And if you don\u2019t know the answers, that\u2019s okay too\u2014we\u2019re here to help.<\/p>\n

    Wait, let\u2019s wrap this up. Gas permeability of plastic film isn\u2019t just some tech buzzword\u2014it\u2019s the reason the products we use every day work as well as they do. It\u2019s a balance of polymer type, thickness, processing, and testing, and getting that balance right can make or break a product\u2019s shelf life, safety, and success. As a plastic film supplier, my job isn\u2019t just to sell you a roll of film\u2014it\u2019s to help you pick the right one for your specific needs, no jargon, no guesswork.<\/p>\n

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    If you\u2019re working on a project and need a film with the right gas permeability, or you have questions about anything we talked about today, don\u2019t hesitate to reach out. We can send free samples, run tests, walk through all the options, whatever you need. Let\u2019s make your product work as well as it can.<\/p>\n

    Mailing Bags<\/a> References<\/p>\n