Acrylic pressure sensitive adhesives (PSAs) were prepared by UV polymerization under varying curing conditions of both fast and slow curing, employing high- and low-intensity UV radiation, respectively. The influences of curing conditions and isobornyl acrylate (IBOA) content on PSA performance were comprehensively investigated by measurement of their rheological, thermal, and adhesive properties. In particular, rheological characterization was accomplished by several analytical methods, such as in situ UV rheology, frequency sweep, stress relaxation, and temperature ramp tests, to understand the effect of the UV curing process and IBOA content on the viscoelastic behavior of acrylic PSAs. The slow-cured samples were observed to form more tightly crosslinked networks compared to the fast-cured. On the other hand, at high loading levels of IBOA, in the case of slow curing, the sample exhibited a contrasting trend, having the shortest stress relaxation time and the highest energy dissipation; this was due to molecular chain scission occurring in the crosslinked polymer during UV polymerization. Consequently, we successfully demonstrated the influence of monomer composition of acrylic PSAs, and that of curing conditions employed in UV polymerization. This study provides valuable insights for the development of crosslinked polymer networks of acrylic PSAs for flexible display applications.
Keywords: UV polymerization; flexible displays; pressure sensitive adhesives (PSAs); rheological properties; viscoelasticity.
© The Polymer Society of Korea and Springer 2021.