Photopolymerizable Adhesives

The above photopolymerizable adhesives can be broadly included within the glass of hydrogels even if the hydrophilic components are a material such as polyethylene glycol substituted for water. 

Some of them (adhesives, coatings, foam plastics, and resins) use Mannich bases or their derivatives as structural components of the material, whereas all the listed branehes are concerned with the use of important additives (mainly antioxidants) or auxiliaries such as basic catalysts and accelerators. Specific functions are performed, for instance, by agents improving the adhesion of photopolymerizable paints and by accelerator-modified adhesion promoters for mbber-to-wirc adhesion." ... 

In the 2P process (4), a thin photopolymerizable liquid layer is cured in situ between a smooth substrate (cut from a polymer sheet or molded) and a master and stripped off to effect pattern transfer. The liquid layer ensures accurate, defect-free replication. Examples of solvent-free formulations include multifunctional acrylates with adhesion, wetting, and release agents. Free radical and cationic polymerization processes have been described (9). At the present disk volume levels, this method is claimed to be cost competitive with injection molding. 

The photopolymerizable composition can be used both as liquids to coat a substrate with light sensitive films and as dry photoresist films. In the latter case, the photoresist is a trilayer pie consisting of a top layer made of poly (ethylene terephthalate), a middle layer being the photopolymerizable composition, and an underlayer made of polyethylene. The underlayer is removed before exposure and the remained bilayer composite is laminated onto a clean substrate. The article is prebake to anneal a polymer layer and to enhance adhesion to the substrate. The selective exposure by the UV light through the top layer hardens the exposed areas of the photoresist. After exposure, the top layer is removed and the photoresist layer... 

It is however, with the more complex and comprehensive investigation of ternary systems that this molecular mechanics approach started to yield results of greater interest on the fundamental principles of adhesion [32]. Ternary systems present two interfaces because they are composed of three molecular species, namely the cellulose substrate, a photopolymerizable primer resin, and a top coat alkyd/polyester varnish [32]. This work was started mainly to address the concept of flexibility of a surface finish system on lignocellulosic materials but led to some unexpected and rewarding results on adhesion too. Examples of the visualization of the conformations of minimum energy of ternary systems are shown in Figs. 4-6. 

---