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We all like the "new car" taste. However, this is really difficult to describe. This is because the well-known intoxicating smell is actually a by-product of man-made materials. Fresh paint, carpet, foam, adhesives and a large number of other man-made substances will emit a stronger smell when new. but why?

Outgassing (or outgassing) is the source of these odors. When plastics undergo extrusion or injection molding processes, they trap tiny gases as they solidify. Heat, sunlight and time will cause these trapped bubbles to expand and blow out micropores on the plastic surface, releasing gas-degassing.

New glues, finishes, and laminate polymers may also contain gas trapped microscopically in the material. Regardless of the form of the material, these gases will slowly escape into the air. We can smell some of them. Over time, the gas will dissipate completely and the smell will disappear.

This is a particularly troublesome problem with pressure-sensitive adhesive (PSA) labels, and any appliance manufacturer that uses plastic will tell you. The smell itself is not the only problem. The trapped gas gradually escaping from the injection-molded thermoplastic can cause bubbles to form under the adhesive label. This is not a problem in porous labels, but stickers, tapes, and protective laminates are usually hermetically sealed.

You are full of hot air!

As we all know, strong ultraviolet radiation and high temperature will accelerate outgassing, which will make blistering and delamination problems more obvious. The automotive industry knows this because engine heat and harsh sunlight often put the most pressure on labels.

Modern cars are increasingly filled with low surface energy thermoplastics, which release gases. For example, injection-molded polycarbonate is the main material for headlamp lenses and optical reflectors. Acrylic, polypropylene and polyamide are also to blame. As we all know, many thermoplastic polyolefin compounds and polyurethanes used in automobile bumpers emit a large amount of exhaust gas.

At the same time, the car also has complete required labels, such as:

Car labeling is also a meticulous work. Many of these key labels must already compete with challenging curvature, low surface energy, exposure to chemicals, contaminants, weather, abrasion, and high temperatures. What should the car manufacturer do to add degassing to the mixture?

To prevent unsightly bubbles from appearing—or worse, labels and laminates peeling off—the manufacturer has invested in research and development.

In fact, any plastic (thermoplastic or thermoset) can obtain a "honeycomb" structure by injecting air during the formulation process. The term mainly refers to plastic foam. However, porous plastics can be rigid or flexible, lightweight or dense, bulky or thin. It all depends on the materials and processes that make them honeycomb.

Some automotive data tag suppliers have carefully designed adhesive carriers made of extremely fine-pored polymers. These "bubble-free" films allow air to pass through without creating any visible holes on the surface. To the naked eye, the best example looks like any other smooth, sealed sticker. However, when you stick the sticker on the surface with the air pocket in the middle, the difference is obvious. Press it and the bubbles will disappear.

How did they do it? Well, there are actually several technologies at work. These composite pressure-sensitive films are made by laminating a surface substrate with a honeycomb film (usually polyester). Any outgass generated by the substrate (or bubbles trapped during application) can pass through the honeycomb structure membrane. Blisters and bubbles disappear quickly with a little pressure.

In addition, the special cavitation bottom layer is designed with an ingenious lateral air release mechanism: micro-channels formed on the surface of the adhesive allow air to escape from the side of the label, and when the exhaust gas flows to the edge, it remains flush with the surface.

These honeycomb films and laminates are ideal label materials for non-bubble applications and long-term bonding on high outgassing plastics. They have been quickly used for various non-foam stripes, stickers and label surface substrates. Electrical appliance manufacturers often use cellular PSA to make large nameplates or application graphics on polycarbonate. Engine hoods and polyurethane bumper stripes in the automotive industry all rely on exhaust-friendly films.

The potential uses in other industries—construction, eyewear, retail, aerospace, toys—are almost limitless. These polyester films are not only suitable for curved surfaces, but also have excellent mechanical strength, heat resistance and smoothness. According to its use, the film can be made transparent, opaque, shiny, matte, textured, and even with a metalized finish that does not affect air permeability. The surface base layer and adhesive layer should also be carefully matched to the needs of the application.

All in all, for PSA labels, degassing does not seem to be as troublesome as it used to be.

The author is the account manager of Lintec Automotive.

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