Abstract
UV-crossinkable pressure-sensitive adhesives (PSA) materials are called, in the adhesives trade photoreactive self-adhesive. UV-crosslinkable PSAs are designed after the UV-initiated crosslinking reaction to stick to almost any surface by a simple contact under light pressure. This special class of adhesives does not undergo any physical transformation or chemical reaction during the bonding process. Because of the rheological properties the adhesive must be fi nely tuned for the application, combining a carefully chosen polymer architecture and monomer composition with the proper addition of small additives called photoinitiators. The best way is using the unsaturated copolymerizable photoinitiators and their direct incorporation into polymer chain during the polymerization process. Progress in the coating technology and the development of novel photoreactive acrylic adhesives will open the door to new applications and an extended market penetration of UV-crosslinkable acrylic adhesive raw materials containing unsaturated copolymerizable photoinitiators incorporated into the polymer backbone. Photoreactive UV-crosslinkable acrylic PSA are characterized by good tack, good adhesion, excellent cohesion and very low shrinkage.
Highlights
Among the different classes of adhesives, pressure-sensitive adhesives (PSA) are perhaps the most common type found in consumer products
The relevant properties of crosslinking solvent-borne acrylic PSA like tack, peel adhesion, shear strength and shrinkage have been evaluated according to test procedures established in the industry
Solvent-borne acrylic PSAs with high performance being used in the PSA-technology shall be distinguished by very high shear strength (120 N at 20°C, 40 N at 70°C)
Summary
Among the different classes of adhesives, pressure-sensitive adhesives (PSA) are perhaps the most common type found in consumer products. The today known UV-crosslinkable solvent-borne acrylic systems contain photoreactive groups as an unsaturated photoinitiator incorporated into the polymer chain during PSA synthesis. Photoreactive solvent-borne acrylic PSA are not commercially available on the market for the production of pressure-sensitive adhesive tapes, labels and medical products. The crosslinking mechanism of photoreactive acrylic PSAs, containing photoreactive benzophenone derivatives incorporated into polymer backbone has been thoroughly investigated. It is presented schematically (Fig. 1)[2]. The dry self-adhesive acrylic films were crosslinked using the UV lamp Aktiprint-Mini 18–2 from Technigraf (Fig. 2) by different UV-dose and different UV crosslinking time. Peel adhesion, shear strength and the shrinkage of UV crosslinked self-adhesive layers were tested
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