Coated vs. Uncoated PP Woven Fabric: When You Need Lamination

Key Takeaways

• Coating and lamination are not the same process. Extrusion coating applies molten polymer directly to the woven fabric. Lamination bonds a pre-formed film, which may be BOPP, LDPE, Kraft paper or another substrate, to the surface. Both close the weave, and the resulting surfaces differ.
• A barrier is a trade, not an upgrade. Closing the weave sharply reduces air and water permeability, which is a benefit for hygroscopic products. If the product has to drain or respire, a barrier is the wrong construction.
• Uncoated is the correct answer more often than buyers assume. For geotextile, silt fence and ground cover, permeability is the function rather than a shortcoming.
• Coating weight is the specification buyers forget. State it in GSM separately from fabric GSM, because two fabrics described as coated can behave completely differently in service.
• If you need both barrier and airflow, micro-perforated laminated fabric gives controlled ventilation while retaining most of the moisture resistance.

Two opposite mistakes cost money in this decision, and only one of them ever shows up on an invoice. Laminating fabric that never needed a barrier is money spent on a property the application does not use, and the product still works, so nobody investigates. Leaving fabric bare where moisture protection was critical costs far more, in caked product, mould, spoilage and rejected loads, and by then the specification is months old. As a manufacturer producing both coated and uncoated woven polypropylene, we see specifications land on the wrong side of this line in both directions. The root cause is usually vocabulary: buyers specify by a word rather than by a property. This guide sets out what each construction physically is, when each is right, and the one specification most buyers omit.

Is coated the same as laminated?

No. They are two different processes producing two different surfaces, and using the terms interchangeably on a purchase order is how buyers receive something other than what they pictured.

Extrusion coating applies molten polymer, usually polyethylene or polypropylene, directly onto the woven fabric, where it cools and bonds into the weave. The result is a sealed fabric with a slightly textured surface that still follows the contour of the underlying tapes.

Lamination bonds a separately manufactured film to the fabric surface. For packaging applications, lamination can involve BOPP, LDPE, Kraft paper or other substrates, depending on the barrier, surface and handling characteristics required.

BOPP is the substrate that matters most where print is the driver. It is biaxially oriented and arrives at the process already formed, so the film is smooth before it is applied and the finished surface is smoother than an extrusion coating. That is why BOPP lamination is the route to high-definition and reverse-printed graphics, while an LDPE or Kraft laminate is usually chosen for barrier, strength or surface reasons rather than for print.

The term that causes the most trouble is “poly-coated”, which is genuinely ambiguous. It is used to mean PE extrusion coating, and it is also used loosely for any polymer barrier including a laminate. Writing it on a specification without qualification means the supplier has to guess.

What does a coating actually do?

It converts a permeable woven textile into a barrier. That is the whole function, and describing it as a trade rather than an upgrade is the most useful framing a buyer can hold onto.

What you gain is water resistance, since the closed surface stops liquid passing through the weave; sift-proofing, because fine particles that would otherwise migrate through the interstices between tapes are contained; a smoother and more printable surface; and a wipeable exterior where hygiene matters. What you pay for it is a small addition to total fabric weight, slightly reduced flexibility, and the property you cannot get back.

That property is permeability. Uncoated woven polypropylene is breathable by design, because the weave has openings between the tapes. Coating and lamination reduce the open permeability of woven fabric by creating a continuous polymer or film layer, so air and water movement through the fabric is substantially lower. Where controlled airflow is required, micro-perforation can be added to provide ventilation while retaining a degree of barrier protection. What no coating weight will do is turn a sealed construction back into an open weave, so if the product has to drain or respire, a barrier is the wrong starting point.

When should fabric stay uncoated?

Whenever permeability is the function rather than a defect. This is where over-specification happens, and it happens because “coated” sounds like a better version of “uncoated” to anyone not familiar with the application.

• Geotextile and silt fence. The entire mechanism depends on water passing through while sediment is retained. A coated silt fence fabric does not filter, it dams, which changes the hydraulic behaviour of the installation and can cause failure. See silt fence specifications.
• Ground cover and landscape fabric. Water and air have to reach the root zone. A barrier here defeats the product. See landscape fabric specifications.
• Breathable covers and produce packaging. Anything that respires or that would sweat inside a sealed bag needs the weave open.
• Aggregates, sand, gravel and coarse non-hygroscopic product. Particle size is well above the weave openings and the product does not care about ambient humidity, so a barrier buys nothing.
• Secondary packaging where an inner liner does the barrier work. If a sealed liner is already inside, coating the outer bag duplicates a function that is already covered.

The last case is the most common source of avoidable cost. A laminated outer bag plus a sealed PE liner is sometimes genuinely specified for belt-and-braces protection of a high-value product, and sometimes it is simply two people solving the same problem without talking to each other.

When do you need a coating or lamination?

When the product is moisture-sensitive, or when the bag has to carry quality print. Those two drivers cover the large majority of legitimate barrier specifications.

On the moisture side, the candidates are hygroscopic and moisture-reactive products: cement, fertiliser, urea, industrial chemicals, food ingredients and pet food. Add to that any product facing humid transit, extended container freight through tropical routes, or outdoor and long-duration storage, where ambient conditions rather than the product itself drive the requirement. See fertilizer bag construction for a worked case.

On the print side, the driver is different. A retail-facing or brand-critical bag needs a substrate that can hold definition, and woven texture limits what flexographic printing can resolve. If the packaging is doing marketing work rather than only containment work, lamination is usually the route. See laminated PP woven bags.

How much coating weight do you need?

Enough that the barrier survives the handling the bag will actually see, and it has to be stated in GSM separately from the fabric weight. This is the specification buyers most often omit, and the omission is why two products both correctly described as “coated” can perform completely differently.

Consider two fabrics both specified at a total of 100 GSM. One is 90 GSM fabric with a 10 GSM coating; the other is 75 GSM fabric with a 25 GSM coating. Both are coated. Both meet a total-weight specification. The first has a thinner barrier over a stronger scrim, the second a more durable barrier over a lighter one. They are not substitutes, and a specification written only as total GSM cannot distinguish them.

Four factors drive how much coating weight an application needs:

• Abrasion in service. Bags that slide, are dragged, or carry an abrasive product wear the coating rather than the fabric, and a thin coating wears through to the base scrim first.
• Folding and creasing. Coating is most vulnerable at fold lines, where it is stressed in a way flat testing does not reveal. Bags that are folded flat for storage and then filled see this repeatedly.
• Handling cycles. A bag handled once is a different duty from one that is stacked, restacked, shipped and stored.
• Heat exposure. Coating can pick up on hot equipment and can soften in high-temperature storage, both of which degrade the barrier.

What if you need both a barrier and airflow?

Micro-perforated laminated fabric is the usual answer. The laminate provides the barrier, and a controlled pattern of perforations allows a defined amount of air exchange, giving you ventilation without returning to a fully open weave.

The applications are mostly agricultural: seed, onions, potatoes and other commodities that respire in storage and will sweat and rot inside a fully sealed bag, but that also need protection from bulk water and contamination. The trade-off is honest and worth stating plainly. Perforation reduces barrier performance against moisture vapour, so a micro-perforated laminate is a compromise between two requirements rather than a way of having both at full strength. Specify it where the product respires, not as a hedge.

Does coating change how the fabric prints?

Yes, and surface smoothness is the governing variable. The print process is broadly the same; what changes is how much definition the substrate can hold.

Uncoated woven fabric takes flexographic print perfectly well, and for text, simple logos and solid blocks of colour it is entirely adequate. What limits it is the woven texture: fine detail, small type and photographic images break up because the surface itself is not continuous. Extrusion-coated fabric gives a smoother and more continuous surface, which lifts achievable definition into the range most industrial packaging needs. BOPP lamination gives the highest definition, because the film arrives smooth and can carry reverse-printed graphics of effectively photographic quality.

The practical guidance is to let the print requirement drive the construction when print matters, rather than choosing a construction and then discovering what it can print. See printing on woven PP.

How should you write the specification?

State the properties rather than a single word. A complete fabric specification for this decision covers eight lines, and the third one is the one usually missing.

If any line is genuinely unknown, state the application instead of guessing a number. “Packing urea for 90 days of covered outdoor storage in a humid coastal climate” tells a supplier more than a coating weight copied from an unrelated specification, and it lets them propose a construction rather than quote a guess. For related requirements see UV stabilisation for outdoor fabric, what PP woven fabric is, and fabric testing standards.

Common specification mistakes

• Writing “laminated” when you mean sealed. If the primary requirement is moisture or dust resistance rather than premium graphics, extrusion coating can be a cost-effective option when the application primarily requires moisture resistance rather than a premium print surface..
• Specifying a barrier on a permeable product. Most often seen on ground cover and drainage applications, where it defeats the mechanism entirely.
• Giving total GSM only. Total weight cannot distinguish a thin coating on strong fabric from a thick coating on light fabric.
• Doubling up on liner and lamination without deciding which does the work. Legitimate for some high-value products, wasteful when it happens by accident.
• Ignoring fold lines. Coating fails at creases before it fails on flat faces, so bags stored folded need the duty assessed accordingly.

Why global buyers choose Anita Plastics

Buyers across North America, South America, Europe, the Middle East, and Asia work with Anita Plastics for woven polypropylene fabric and bags because:

• Backward-integrated manufacturing from resin to finished fabric, backed by a parent group with more than four decades in woven polypropylene.
• Uncoated, extrusion-coated and BOPP-laminated constructions produced in-house, so the recommendation is not constrained by what one process line can make.
• Custom fabric weight, coating weight, coated sides, UV package, width and perforation specified to your application.
• US warehouse stock in Charleston, South Carolina, with blind and drop shipping for stock constructions.
• Certified, spec-ready production including food-grade lines, with specification documentation supplied on request.
• Technical support at the specification stage, including recommending a construction from the application when the spec is not settled.

If you are unsure whether your application needs a barrier at all, send us the product, the storage and transit conditions, and how the bag or fabric is handled, and we will specify the construction and the coating weight. Contact Anita Plastics for a spec sheet or a quote.

Frequently Asked Questions

Is coated the same as laminated?

No. Extrusion coating applies molten polymer directly onto the woven fabric. Lamination bonds a pre-formed film, which may be BOPP, LDPE or Kraft paper, to the surface. Both close the weave, but a BOPP laminate gives a smoother, higher-definition print surface. State which process you require rather than writing “poly-coated”.

Does coated fabric still breathe?

Standard coated or laminated fabric has substantially lower air and water permeability than uncoated woven fabric, because the surface is covered by a polymer layer or film. That applies to both extrusion coating and lamination. Where controlled ventilation is required, micro-perforation can be incorporated to provide airflow while retaining some barrier protection.

How much coating weight should I specify?

It is driven by abrasion, folding, handling cycles and heat exposure rather than by a default. State it in GSM separately from fabric weight, because two fabrics at the same total weight can carry very different coatings and will not perform the same in service.

Can uncoated fabric be printed?

Yes, flexographic printing works well on uncoated woven PP for text, logos and solid colour. Definition is limited by the woven texture, so fine detail, small type and photographic images are where an extrusion coating or a BOPP laminate becomes necessary.

Does lamination weaken the fabric?

No. Tensile strength comes from the woven scrim and is not reduced by adding a laminate. Flexibility is slightly reduced and the fabric becomes marginally heavier, but the load-bearing performance of the base fabric is unchanged.

Should I coat the bag if it already has a liner?

Usually not, unless the product genuinely warrants redundant protection. A sealed inner liner already provides the moisture barrier, so coating the outer bag duplicates that function. Decide deliberately which component does the barrier work rather than specifying both by default.