Plasma treatment solves the single biggest headache in flexible packaging converting: getting inks, coatings, and adhesive laminations to stick reliably to low-surface-energy polymer films. By bombarding the film surface with reactive plasma species, you raise surface energy from a typical 30–34 dyne/cm on untreated BOPP or PE to well above 50 dyne/cm — the threshold where solvent-based, water-based, and UV inks wet out fully and bond permanently. Unlike corona treatment, plasma gives you tunable chemistry, longer-lasting activation, and none of the backside-treatment headaches that plague thin-gauge webs. This guide walks you through the science, the practical integration steps, and the real performance differences you can expect on your converting line.
Polyolefin films — BOPP, LDPE, LLDPE, CPP — are the workhorses of flexible packaging. They're cheap, they run well on high-speed machinery, and they have excellent barrier properties. But they share one critical flaw: extremely low surface energy. Untreated polyethylene sits around 31 dyne/cm. Untreated polypropylene hovers near 29 dyne/cm. For comparison, most printing inks need a substrate surface energy of at least 38–42 dyne/cm to wet out properly, and high-performance adhesive laminations want 46 dyne/cm or above.
When surface energy is too low, ink droplets bead up instead of spreading. Coatings crawl. Lamination adhesives form weak bonds that fail during pouch-filling or end-use handling. You see it as smearing during the tape-pull test, delamination at seal jaws, or — worst case — ink transfer onto food contact surfaces.
It's tempting to think roughening the surface would help. It doesn't — not meaningfully. The problem is that polyolefins are essentially inert hydrocarbons with no polar functional groups. Adhesion requires chemical interaction: hydrogen bonding, dipole–dipole forces, or covalent bonding at the interface. Without oxygen-containing or nitrogen-containing functional groups on the film surface, there's nothing for the ink binder to grab onto. That's the gap plasma surface treatment technology is designed to close.
Plasma treatment works by generating a highly reactive ionized gas — containing free radicals, UV photons, ions, and metastable species — and directing it at the film surface. Within milliseconds of exposure, three things happen simultaneously:
This is where plasma pulls ahead of corona. With corona, you're stuck with ambient air — you get a mix of oxidation products, and you can't control what functional groups dominate. With plasma, you choose the process gas. Compressed dry air or oxygen plasma gives you carbonyl and carboxyl groups — ideal for solvent-based inks. Nitrogen or nitrogen/hydrogen mixtures graft amine groups that dramatically improve adhesion of water-based inks and certain polyurethane adhesives. This tunability means you can match your surface chemistry to your specific ink or coating system.
Most flexible packaging converters already have corona treaters. They work. So why consider plasma? Because “works” and “works reliably across every SKU and every season” are different things.
Corona treatment has three well-known limitations on packaging films:
Atmospheric plasma systems confine the discharge to a narrow, controlled zone — no backside treatment, period. Treatment longevity is typically 2–4× longer than corona because plasma grafts more stable functional groups deeper into the surface. And because the plasma jet or array geometry is precisely engineered, you get uniform treatment edge-to-edge.
The comparison table below summarizes the key differences:
A mid-size European converter running metallized BOPP for snack food wrappers was experiencing chronic ink adhesion failures. Their existing corona system treated the film to 40–42 dyne/cm at the treater station, but by the time the rolls reached their gravure press — sometimes 48 hours later — surface energy had decayed to 35–37 dyne/cm. The result: failed tape-pull tests on roughly 12% of production, leading to costly reprints and customer complaints.
They installed an inline atmospheric plasma unit immediately upstream of the gravure press, using compressed dry air as the process gas. Post-treatment surface energy consistently measured 52–56 dyne/cm — well above the 42 dyne/cm threshold their ink supplier specified. Critically, because the treatment happened seconds before ink contact, decay was irrelevant. Tape-pull failure rates dropped to under 0.3%. The converter also eliminated a primer coat they had been applying as a “safety net,” saving approximately €0.008 per square meter of film — which, at their volumes, paid for the plasma system in under nine months.
This kind of ROI story is common. If you're curious whether your specific film and ink combination would benefit, reach out to our applications team for a feasibility assessment.
Not all films respond identically to plasma. Here's a practical breakdown of the most common flexible packaging substrates and what works best:
BOPP is the most widely plasma-treated packaging film. Untreated surface energy: ~29 dyne/cm. Target after treatment: 48–56 dyne/cm for gravure and flexo inks. Oxygen or air plasma at moderate power density (1–3 W/cm²) and exposure times of 0.1–0.5 seconds at web speed works well. Over-treatment causes surface embrittlement — stay below 5 W/cm².
PET starts higher at ~42 dyne/cm untreated, but barrier coatings and adhesive laminations often need 54+ dyne/cm. PET responds quickly to plasma — short exposure times suffice. Nitrogen plasma can be particularly effective for improving adhesion of AlOx barrier coatings.
PE is the most challenging. Its branched, non-polar structure resists functionalization. You need higher power density or slower line speed to achieve equivalent results. Air plasma typically gets PE to 48–52 dyne/cm. For adhesive lamination applications requiring 56+ dyne/cm, nitrogen/hydrogen mixed gas plasma is the better choice.
These films already have moderate surface energy due to inherent polar groups. Plasma treatment is still valuable for removing slip agents and antiblock additives that migrate to the surface during storage and degrade adhesion. A light plasma cleaning pass is usually sufficient.
The best plasma treatment in the world is useless if it's installed in the wrong place or configured for the wrong line speed. Here are the integration principles that matter most:
Treatment decay starts immediately. Every meter of web travel between the plasma unit and the ink applicator is wasted activation. Ideally, the plasma head sits within 0.5–2 meters upstream of the first print station. This eliminates the decay problem entirely and means you don't need to over-treat to compensate.
Atmospheric plasma systems are rated for specific treatment doses, measured in W·min/m². If your line runs at 300 m/min, you need a plasma array with enough power density to deliver the required dose at that speed. Undersizing the plasma unit is the most common integration mistake — the system technically runs but delivers insufficient treatment at full production speed. Always specify your maximum line speed, not your average.
PPlasma heads generate heat. On thin films, web speed, cooling distance, and dwell time must be carefully controlled to avoid shrinkage, warping, or surface damage.
For a deeper look at what inline integration involves, explore our system capabilities page.
You can't manage what you don't measure. And in flexible packaging, the consequences of under-treatment — rejected print runs, delaminated pouches, customer complaints — are expensive enough that you need real verification, not assumptions.
Dyne ink pens are the most common shop-floor test. Apply a line of ink rated at your target dyne level; if it wets out and stays wetted for 2+ seconds, you're above that level. The problem: dyne inks are subjective, operator-dependent, and destructive (they contaminate the surface). They're fine for spot checks but inadequate for process control.
Automated contact angle goniometers — including inline models — measure the wetting angle of a water droplet on the treated surface. A contact angle below 30° on BOPP typically corresponds to surface energy above 50 dyne/cm. Inline goniometers can measure every few seconds and feed data back to the plasma system controller for closed-loop power adjustment. This is where the industry is heading in 2026, and it's worth the investment for high-volume converters.
When adhesion problems persist despite apparently adequate dyne levels, surface chemical analysis via X-ray photoelectron spectroscopy (XPS) or ATR-FTIR can reveal whether the right functional groups are present. For instance, you might have adequate total surface energy but insufficient carboxyl groups for your specific ink chemistry. These are lab tests, not production tests, but they're invaluable for troubleshooting. Our applications engineering resources can help interpret results.
Plasma treatment isn't magic — it's chemistry and physics. And like any process, it fails predictably when certain rules are broken. Here are the mistakes we see most often:
Plasma can clean light contamination, but heavy slip agent bloom, silicone release coatings, or oily residues from upstream processes overwhelm the treatment. If your film has visible contamination or has been stored in warm conditions that accelerate additive migration, a dedicated plasma cleaning pass before the activation pass may be necessary.
Atmospheric plasma systems are sensitive to moisture in the process gas and ambient air. High humidity introduces water vapor into the plasma, shifting the chemistry toward hydroxyl-heavy functionalization and reducing the density of carboxyl groups. In tropical or poorly climate-controlled facilities, drying the process gas is essential for consistent results.
Even plasma-treated surfaces decay. Polymer chains rearrange, burying polar groups beneath the surface — a phenomenon called hydrophobic recovery. On BOPP, you can lose 10–15% of your surface energy gain within 72 hours. The solution is simple: treat inline, immediately before printing or coating. If that's not possible, store treated rolls in sealed polyethylene bags to slow oxidation-driven rearrangement.
Air plasma works for most solvent-based inks. But if you've switched to water-based inks and your adhesion has gotten worse, your surface chemistry might be wrong — not your surface energy level. Water-based inks often bond better to amine-functionalized surfaces than carboxyl-functionalized ones. Switching from air to nitrogen plasma can solve the problem overnight.
Flexible packaging is under intense pressure to become more sustainable, and that pressure is actually accelerating plasma adoption. Here's why:
The push toward recyclable mono-material packaging — all-PE or all-PP structures replacing multi-material laminates — creates new adhesion challenges. Mono-material films often have lower inherent surface energy and fewer built-in adhesion promoters than traditional multi-layer structures. Plasma treatment is emerging as the enabling technology that makes printable, coatable mono-material packaging viable at commercial scale.
Many converters use solvent-based primers to boost adhesion on difficult substrates. These primers add cost, add a process step, emit VOCs, and complicate recycling. Plasma treatment can replace primers entirely in many applications — as the snack food converter case above demonstrated. With EU packaging regulations tightening in 2026 and EPR schemes penalizing non-recyclable components, eliminating primer layers has both environmental and financial benefits.
Plasma treatment adds no chemicals to the film surface — it modifies the existing polymer chains. This is a significant advantage for food contact packaging, where migration testing and regulatory compliance (EU 10/2011, FDA 21 CFR) add cost and complexity for any added layer. Plasma-treated surfaces are inherently compliant because nothing has been deposited.
For detailed technical documentation on plasma treatment processes, visit our whitepapers and datasheets library.
Choosing between atmospheric and low-pressure plasma — and sizing the system correctly — depends on three variables: your line speed, your film portfolio, and your adhesion targets.
Atmospheric plasma is the only practical option. Look for modular plasma arrays that can be ganged together to cover your full web width (typically 800–1600 mm for packaging lines). Power density should be adjustable to accommodate different film types without changing hardware. Closed-loop control via inline contact angle measurement is a strong investment for operations running multiple SKUs.
For specialty applications — medical packaging, high-barrier coatings, or small-batch premium packaging — low-pressure plasma in a vacuum chamber offers the highest treatment quality and the most precise gas chemistry control. Treatment uniformity is exceptional, and you can treat 3D-formed trays or pre-made pouches, not just flat webs.
No reputable plasma equipment supplier should ask you to buy a system without first running trials on your actual films with your actual inks. Insist on pilot testing — either at the supplier's lab or with a rental unit on your line. Measure adhesion with standardized tests (ASTM D3359 tape pull, ASTM F2255 peel strength) before and after treatment. The data will tell you exactly what power level, gas type, and treatment dose you need.
If you're evaluating plasma for your flexible packaging line, contact fariplasmatech to discuss your specific films, inks, and production requirements. We'll help you determine the right system configuration and run pilot trials so you can make a decision based on data, not guesswork.
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