Pressure sensitive adhesives are usually polymerized in the presence of solvent but the evaporated solvent vapors contaminate the atmosphere and there required large amounts of energy to evaporate the solvents which costs high. And the other point emphasized on the present paper is plasticizer migration to the acrylic pressure sensitive adhesive when applicated to the plasticized vinyl substrate.
The acryl monomers were partially polymerized under UV radiation. However there was a limitation of UV penetration. It was difficult to polymerize acryl monomers on a large scale.
For the above reason, the acrylic pressure sensitive adhesive was polymerized in solution. In the solution polymerization, the 2-ethylhexyl acrylate and acrylic acid monomers were polymerized in ethylacetate and toluene and the remaining solvents were fully eliminated by precipitation and rotary evaporator. The viscosity near around 1200~1,500cps was adjusted by adding 1.85 times of above monomers.
And UV polymerization was executed under UV radiation adding the benzyl dimethyl ketal as a photoinitiator, HDDA as a crosslinker and silica. The silica was added to study the effect on adhesive properties. The silica interacted with acrylic acid by hydrogen bonding to make hydrophilic domain and the hydrophobic domain by phase seperation.
When the wettability increases usually the cohesive strength decreases. However, the addition of silica increased both properties by phase seperation and hydrogen bonding.
