Significant Differences in Structure and Properties of Cast Film Prepared by Solution Casting and Coat Layer Prepared by Solution Coating of Block Copolymer Adhesives

This study reports significant differences in the structures and properties of test specimens of block copolymer adhesives prepared according to two different methods, solution casting and solution coating. To evaluate the mechanical properties of a pressure-sensitive adhesive (PSA), test pieces are generally prepared by solution casting (solvent evaporation). Thus, the obtained specimen is completely different from the PSA layer of an actual PSA tape, which is commonly prepared by solution coating. This concept of equivalence of the two PSA test pieces is commonly adopted by engineers in PSA production companies, and violation of this concept may critically affect their research and development activities. In this current study, it was found that the surface segregation of the tackifier influenced the viscoelastic behavior of cast films, and the peak-top temperature of the loss tangent (tan δ) was lower than that of the corresponding coat layer. Additionally, conditions were derived experimentally for the commonly used solution casting, by which mechanical properties equivalent to those of the test piece prepared by solution coating were accidentally obtained. This outcome of the current study can greatly contribute to the community of the PSA industries.