Adhesive & Self-Adhesive Terms

How self-adhesive Flexstone is built and tested: permanent PSA, water-based removable WRA, dot-pattern air-release DPA, release liners, and the holding-power and rolling-ball tack figures on the specification sheets.

PSA (Permanent Pressure-Sensitive Adhesive)

A pressure-sensitive adhesive bonds under light pressure without water, solvent or heat. In Flexstone part numbers, PSA denotes a middle-tack permanent adhesive with medium initial adhesion and a non-carrier design. It adheres easily to mostly smooth surfaces and, once fixed, sticks firmly and is not removable. Its rolling-ball initial adhesion is 8–10# steel ball within 100 mm (GB/T 4852-2002).

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WRA (Water-Based Removable Adhesive)

WRA is the water-based, eco-friendly removable adhesive used on Flexstone self-adhesive grades. It has medium tack and is suitable for semi-rough as well as smooth surfaces. The specification sheets give the same adhesion data as for PSA: a 25 × 25 mm area hangs 0.5 kg for 24 hours without slide, and rolling-ball initial adhesion is 8–10# steel ball within 100 mm.

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DPA (Dot-Pattern Air-Release Adhesive)

DPA is a high-tack acrylic removable adhesive applied in a dot pattern on Flexstone Eco-Film. Moderate initial tack allows repositioning during installation, and the channels between the dots let trapped air escape for bubble-free application. It is intended for smooth surfaces and can be cleanly removed for up to 6 months indoors. Rolling-ball initial adhesion is 6–8# steel ball within 100 mm.

Flexstone® Eco-Film DPA

Air-Release Channels

Air-release channels are continuous gaps in an adhesive layer that let air trapped under a film escape toward the edges as the film is squeegeed down. They allow large graphics to be applied dry and bubble-free by non-specialists. On Flexstone Eco-Film DPA the channels are formed by the spaces between the adhesive dots, so no wet application is needed.

Flexstone® Eco-Film DPA

Holding Power (Static Shear)

Holding power, or static shear, measures how well an adhesive resists a constant load applied parallel to the bonded surface over time. A fixed area of adhesive is bonded to a test panel, a weight is hung from it, and any slippage is recorded. For Flexstone PSA, WRA and DPA adhesives, a 25 × 25 mm area hangs 0.5 kg for 24 hours without slide.

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Rolling-Ball Tack (Initial Adhesion, GB/T 4852)

Rolling-ball tack is an initial-adhesion test in which steel balls roll down an inclined plane onto the adhesive surface; GB/T 4852 is the Chinese national standard for the method. The result is given as the ball number the adhesive stops within a set distance, and a larger ball number means higher initial tack. Flexstone PSA and WRA stop an 8–10# ball within 100 mm; DPA stops a 6–8# ball.

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Release Liner

A release liner is the backing sheet that protects a pressure-sensitive adhesive until use and peels away cleanly at application. In a self-adhesive Flexstone construction, the total thickness on the specification sheet covers face film, adhesive and liner: for example, a 0.22 mm face becomes 0.32 mm and the K-coated PSA faces of 0.15 mm and 0.20 mm become 0.25 mm and 0.30 mm in the wide-format grades, while in narrow-web label stock a 0.15 mm face becomes 0.23 mm and a 0.20 mm face 0.28 mm.

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