Preparation and Properties of Dual Cross-Linking Acrylic Pressure-Sensitive Adhesives for Flexible Displays

Abstract

Aiming to satisfy the requirements of pressure-sensitive adhesives (PSAs) for flexible displays, 2-[[[6-[3-(6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl)ureido]hexyl]carbamoyl] oxy]ethyl acrylate (Upy-HDI-HEA) was synthesized, and a series of dual cross-linking EHA-co-HEA copolymers with multiple hydrogen bonds were prepared. The effects of the Upy-HDI-HEA content on the EHA-co-HEA copolymers’ chemical structure, thermal properties, viscoelasticity, mechanical properties, and adhesion performance were comprehensively investigated via in situ Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC), mechanical testing, and adhesion testing. The multiple hydrogen bonds acting as strong physical cross-linking enhance the deformation resistance of EHA-co-HEA copolymers. Moreover, compared to chemical cross-linking, the multiple hydrogen bonds allow for a certain degree of unhindered movement and energy dissipation, which benefits the flexibility and peel resistance of EHA-co-HEA copolymers. Consequently, relatively low storage moduli and glass transition temperatures were observed in all EHA-co-HEA copolymers. Young’s modulus, recovery rate, and cyclic stability of EHA-co-HEA copolymers increase with the rising Upy-HDI-HEA content. Also, the loop tack, 180° peel strength, and shear strength of EHA-co-HEA copolymers significantly improved, showing a better adhesion performance than commercial PSAs.