“Design of experiments” analysis in study of solventless UV crosslinkable acrylic pressure sensitive adhesives

A 24 full factorial design was employed in the study of solventless acrylic UV crosslinkable pressure sensitive adhesives. The effect of four different factors (acrylic acid, t-butyl acrylate azobisisobutyronitrile initiator, and chain transfer agent) on different responses (prepolymer viscosities, final overall monomer conversion, tack, peel, and shear strength) was studied. Prepolymers were synthesized using a batch bulk polymerization procedure. The reaction mixture consisted of acrylic monomers (2-ethylhexyl acrylate, acrylic acid, and t-butyl acrylate), azobisisobutyronitrile initiator, chain transfer agent n-dodecylmercaptan, and unsaturated UV photoinitiator 4-acryloyloxybezophenone, which was copolymerized into the polymer backbone. The adhesive properties of the acrylic coatings were evaluated using tack, peel, and shear strength tests. Results showed that statistical analysis of the studied factors on polymer properties meets theoretical expectations. Analysis showed that the acrylic acid and the chain transfer agent (CTA) had the greatest effect on the prepolymer viscosity. None of the factors had a major impact on the final conversion of the synthesized products. The acrylic acid had a significant impact on the adhesive properties of the coating, i.e. tack and peel strength due to molecular hydrogen bonding. The impact of the studied factors could not be ascertained for the shear resistance of the adhesive coating.