Sticky Plastics

Who hasn’t come across that moment when a formerly leather-like, silky-smooth coating on your stuff suddenly turns sticky? If it’s just a ballpoint pen that ends up in the trash because it’s gooey, you shrug it off. But when the kitchen knife holder sticks to the tiles—or worse, your e-book reader or an expensive studio light turns into a sticky mess—that’s when you really lose it.

The recurring problem is the stickiness of soft-touch polyurethane coatings. Some blame formaldehyde emissions from furniture boards, others say it’s because airplanes dump kerosene. Both are conspiracy theories—nonsense.

I’ve also read claims that “contact with the oils in human skin” causes the stickiness, or that it’s due to poor application of the coating (not properly dried during manufacturing). After long research, I concluded that most of what people say on the internet about the stickiness of these items is nonsense.

Hydrolysis

The true culprit behind the stickiness is a highly dangerous greenhouse gas that can even cause suffocation: dihydrogen monoxide—also known as water. Its vapor is indeed the most potent greenhouse gas in the atmosphere, and yes, you can drown in it. If you drink too much, you get hyponatremia (water intoxication), which leads to brain swelling, increased intracranial pressure, heart failure, and potentially death. So, it’s dangerous stuff!

Chemically speaking, water is aggressive. It causes plastic coatings to liquefy and become sticky. These soft-touch coatings are made of polyurethane, which is prone to hydrolysis. During hydrolysis, water molecules bond with the urea linkages in the polyurethane, breaking them down. This alters the molecular structure of the polymer, causing it to lose its strength, become gooey or fragile, or even disintegrate into powder. This is known as “sticky-shed syndrome” (SSS) in magnetic tapes and affected tapes from Maxell, TDK, Kodak, etc., produced in the 2000s (earlier tapes didn’t use polyurethane). The same phenomenon is documented in waterproof coatings on tents and backpacks.

Polyurethane Coatings

Glossy coatings have long been popular with consumers because of their vivid colors, but they easily show scratches, grease, dust, and fingerprints. Matte coatings offer a soft, elegant look and feel, eliminating the drawbacks of glossy surfaces.

Two-component waterborne polyurethane (2K WB PU) coatings appeared in the 1990s for environmental and health reasons, especially to reduce VOC emissions. These are water-based and solvent-free, unlike traditional solvent-based 2K PU coatings. The industry has long struggled with their slow drying and limited hydrolytic stability and durability. Various catalysts are used to improve them, though they pose challenges in terms of chemical compatibility, shelf life, and mechanical performance【1】.

Looking at the Web of Science from 2000 to 2023—especially post-2010—there’s a big spike in publications on polyurethane matte resins. Greenwashing is obvious in articles claiming, for example, that “high-gloss WPU coatings, known for their vivid, shiny colors, are widely used in everyday life. However, their tendency to strongly reflect light often causes discomfort and serious light pollution in urban areas.” Excuse me—how exactly does an e-book reader cause urban light pollution?

Current research on matte WPU resins focuses on adding matting agents or chemically modifying WPU. Physical matting means mixing WPU with matting agents to create a non-uniform film. The matte effect comes from microscopic surface roughness created by carefully controlled particle size and distribution. Common inorganic matting agents include silica; organic ones include polyethylene wax, polypropylene wax, and Teflon wax. However, due to incompatibility between additives and the polymer emulsion, these may produce uneven gloss or a hazy surface. Sometimes the coating turns powdery. I also question the health risks when this dust becomes airborne or contaminates drinking water.

Chemical self-matting modifies WPU behavior, e.g., using epoxy-modified waterborne PU or acrylic resin latex hybrids. These changes cause mechanical stress during film curing, leading to diffuse reflection. The result: lower surface gloss and a strong matte effect. While self-matting has gained attention for its excellent lightfastness and mechanical properties, most coatings are still produced by adding physical matting agents【2】.

For more on polyurethane application developments, I recommend A brief discussion on advances in polyurethane applications【3】. Searching via Google Scholar yields many great articles, mostly on producing water-based PU resins and chemical matting methods. Clearly, hydrolysis of coatings is a known industrial problem—but what’s more important is producing a nice-looking, marketable coating cheaply, not one that lasts for years.

How NOT to Fix the Stickiness

Short version: you can’t fix it. The process is essentially irreversible. If the object tolerates heat, drying it at 50–60 °C for 1–8 hours may offer temporary (weeks to months) improvement, but the PU will reabsorb moisture and become sticky again. Drying doesn’t restore material strength—if hydrolysis is advanced, the dried material may crumble.

To get rid of the stickiness, you must remove the coating. It might not look as good afterwards—but that’s better than losing functionality. Note: button labels may vanish (they’re often printed on the PU layer). You’ll need to either replace them or accept their absence—after all, Soviet T-34 tanks in World War II had no labels on their controls because the crews were assumed to be illiterate.

wikiHow has a removal guide co-authored by Ahmed Mezil, a cleaning expert and CEO of Hellamaid (Ontario). His suggestions—with which I disagree—are as follows:

• Baking soda paste: Mildly abrasive and alkaline. Removes some of the coating, but scratches the plastic underneath. Also corrosive to electronics.
• Alcohol wipe: Ineffective in my experience. May even make things worse by removing surface oils that reduced stickiness.
• Soapy water: Completely useless.

You’d think a cleaning expert would know better. But no—he’s good at selling “expertise.” These methods might work if you’re removing maple syrup, honey, or snot—not aged PU.

One tent-repair blog suggests warm water and ammonia (ammonium hydroxide). They say “use a mask” because of the pungent fumes. Let me add: those fumes are toxic. You don’t need a mask, you need a gas mask! Or better yet, skip this method altogether.

What Actually Worked for Me

1. Tesa® Adhesive Remover 60042: A spray with petroleum, hydrogenated heavy naphtha, and D-limonene (citrus scent). Useful if the item is only slightly sticky and you just want to remove the top layer of the coating. Downsides: expensive and may dissolve some plastics.
2. Isopropyl alcohol: Stronger than the above, but not always fully effective. Suitable for more degraded coatings. Downsides: expensive, toxic, flammable, and may dissolve adhesives used in electronics.
3. Acetone-free nail polish remover: The cheap Spar brand worked best—contains ethyl acetate, denatured alcohol, and water, with some fragrance and color. It evaporates cleanly, doesn’t seem to damage ABS or polyethylene (test first!), and causes the sticky coating to swell and wipe off easily. Use a microfiber, nylon/polyester cloth, or a well-worn handkerchief soaked in the remover. (Note: the cloth will be ruined—bin it after.)

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References:

1. Perez, L. A., & Venham, L. D. (2011). New Water-Soluble Catalyst for Two-Component Waterborne Polyurethane Coatings. PCI Mag. Link
2. Li, Ge et al. (2024). Advances in waterborne polyurethane matting resins: A review. Applied Surface Science Advances, 19, 100557. https://doi.org/10.1016/j.apsadv.2023.100557
3. Das, Abhijit & Mahanwar, Prakash. (2020). A brief discussion on advances in polyurethane applications. Advanced Industrial and Engineering Polymer Research, 3(3), 93–101. https://doi.org/10.1016/j.aiepr.2020.07.002