Coating fabric is a textile that has been treated with a layer of polymer, typically applied to one or both sides, to give it properties the base fabric doesn’t have on its own. Think waterproofing on a rain jacket, UV resistance on an awning, or the slick, wipeable surface of a diaper-changing pad. The base material (usually polyester, nylon, or cotton) provides structure and strength, while the coating adds function.
How the Coating and Fabric Work Together
A coated fabric isn’t just a plastic sheet glued onto cloth. The polymer actually penetrates into the tiny gaps between yarns, filling the porous structure of the textile. This partial absorption is what makes the bond durable and changes how the finished material behaves. The fabric gives the coating something to grip, increasing its toughness, while the coating seals the fabric against water, wind, or abrasion. The trade-off is flexibility: an uncoated nylon is soft and drapes easily, while a coated version feels stiffer because the polymer locks yarns in place.
Common base fabrics include polyester, nylon, and cotton blends. Polyester and nylon are the most popular for outdoor and industrial uses because they’re lightweight, strong, and resist stretching when wet. Cotton-based coated fabrics show up in applications like waxed canvas bags, where a more natural look and feel matters.
Common Coating Materials
Polyurethane (PU)
Polyurethane is the most widely used waterproof coating for fabrics, largely because it’s inexpensive and versatile. PU coatings can achieve very high water resistance ratings, sometimes exceeding 10,000 mm hydrostatic head (a measure of how much water pressure the fabric can withstand before leaking). They also accept fire retardants well, which matters for products that need to meet safety standards.
The downsides are worth knowing. PU is actually hydrophilic, meaning it slowly absorbs water during prolonged contact. A PU-coated tent fly will sag when wet because the coating takes on moisture and stretches. It’s also the least stable of the major coating types over time. Exposure to moisture and heat gradually breaks down the polymer through a process called hydrolysis, which is why old rain jackets eventually start flaking on the inside. PU-coated fabrics are also more prone to mold and mildew than other options.
Silicone
Silicone coatings are chemically inert, hydrophobic, and remarkably long-lasting. Unlike PU, silicone doesn’t absorb water at all, so fabrics coated with it on both sides (called sil/sil) stay taut when wet and resist mold completely. Silicone also does something unusual: it actually increases the tear strength of the fabric it’s applied to, because it allows yarns to slide against each other under stress rather than snapping at a fixed point.
The main limitation is that silicone can’t achieve the very high water resistance ratings that PU can, typically topping out around 1,500 mm on lightweight fabrics. It also can’t be seam-taped effectively, which means manufacturers have to use other methods to seal stitching lines. Despite these drawbacks, silicone-coated fabrics outlast all other coating types under normal conditions.
PVC (Polyvinyl Chloride)
PVC coatings produce a heavy, highly waterproof, and abrasion-resistant material. You’ll find PVC-coated fabrics in truck tarps, inflatable boats, industrial curtains, and heavy-duty bags. PVC is cheap and extremely durable against physical wear, but it’s heavier and less breathable than PU or silicone options, and raises more environmental concerns during production and disposal.
How Coatings Are Applied
The most common industrial method is knife coating, sometimes called blade coating. The process works like spreading frosting with a flat edge: excess polymer is applied to the fabric, and then a precisely positioned blade scrapes off everything above a set thickness. The gap between the blade and the fabric determines how thick the final coating will be, with the wet coating typically ending up about half the size of that gap.
There are several variations. In knife-over-roll, the fabric passes over a support roller while the blade skims the top surface, giving consistent results on smooth fabrics. A floating knife setup presses directly against the fabric, which is held taut between two rollers with no support underneath. This pushes more polymer into the fabric’s structure, creating deeper penetration and a stronger bond. Air knife coating replaces the metal blade with a jet of high-velocity air that blows off excess material, useful for thinner, more uniform layers.
The blade’s shape, angle, flexibility, and the thickness of the liquid polymer all affect how much coating ends up on the fabric and how deeply it soaks in. Manufacturers adjust these variables depending on whether they want a surface-level seal or a deeper impregnation.
Waterproof Ratings and What They Mean
Coated fabrics are rated for water resistance using a measurement called hydrostatic head. Testing is straightforward: a fabric sample is clamped over a sealed tube, water is gradually added, and the height of the water column (in millimeters) at the point the fabric starts leaking is the rating.
Here’s what the numbers translate to in practice:
- 1,000 to 1,500 mm: Handles light showers and brief rain exposure. Fine for fair-weather camping or light-duty covers.
- 2,000 to 3,000 mm: Good for moderate rain and longer wet conditions. A solid minimum for three-season outdoor gear.
- 5,000 mm and above: Excellent waterproofing suitable for heavy rain, sustained storms, and situations where water pools against the fabric.
For context, sitting on wet ground in rain pants creates localized pressure on the fabric, so gear that will see real outdoor use generally needs ratings well above the bare minimum.
Why Coatings Fail Over Time
The most common form of coating failure is delamination, where the polymer layer separates from the base fabric. This shows up as peeling, flaking, or a sticky residue on the coated side. Three things drive it: repeated temperature swings that expand and contract the coating and fabric at different rates, mechanical stress from folding and abrasion, and chemical breakdown from prolonged moisture exposure (especially with PU coatings).
How well the coating was bonded to the fabric in the first place is the single biggest factor in how long it lasts. Higher-quality coated fabrics use surface preparation techniques that maximize contact between the polymer and textile fibers, creating a stronger interface. On the consumer side, you can extend the life of coated gear by storing it clean and dry, avoiding prolonged compression (don’t leave your tent stuffed in a tight sack for months), and keeping it out of sustained heat.
Shifting Away From PFAS Coatings
For decades, many water-repellent fabric coatings relied on a class of chemicals called PFAS, sometimes referred to as “forever chemicals” because they don’t break down in the environment. The regulatory landscape has shifted dramatically. By 2025, France banned PFAS in textiles, Denmark prohibited them in clothing and footwear, and the European Chemicals Agency proposed an EU-wide restriction with strict limits on total fluorine content. In the United States, California’s AB 1817 banned PFAS in textiles, and multiple other states followed with their own restrictions. China classified PFAS as highly restricted toxic chemicals, and Japan regulated them under its framework for specified chemical substances.
This has pushed the industry toward PFAS-free alternatives. Researchers are also developing biodegradable polyurethane coatings built from plant-derived and amino acid-based components, including building blocks derived from lactic acid, glycolic acid, and the amino acid lysine. These materials are designed to break down after disposal rather than persisting indefinitely. The coatings industry is still in transition, but the direction is clear: petroleum-based, persistent coatings are being replaced by options that perform well and leave a smaller environmental footprint.
Common Products Made With Coated Fabric
Coated fabrics are everywhere once you start looking. Rain jackets, tents, and backpacks use PU or silicone-coated nylon or polyester. Upholstery fabrics in restaurants, hospitals, and boats often have PVC or PU coatings for easy cleaning. Automotive airbags use silicone-coated nylon to contain gas under extreme pressure. Industrial conveyor belts, protective clothing, inflatable structures, and outdoor furniture covers all rely on coated textiles to resist water, chemicals, UV light, or abrasion that the base fabric alone couldn’t handle.