Super-strong reusable hot melt adhesives prepared from hyperbranched epoxy resin

Abstract

Hot melt adhesives have been broadly applied in vehicles, electronics, and packaging industries due to their excellent properties of no-pollution, easy-peeling, and little damage to the substrate surface. However, the weak adhesion strength and poor reusability of hot melt adhesives prepared from traditional diglycidyl ether of bisphenol A (DGEBA) greatly hindered their application. Herein, we synthesized a hyperbranched epoxy resin (MHER) by a highly efficient microwave-assisted reaction and constructed a super-strong reusable thermoplastic hot melt adhesive (HEA) through incorporation with DGEBA and a polyether amine bearing the ureidopyrimidinone motif, without the use of any solvent. The synthesis efficiency of MHER was increased about 6.3 times and the tedious process was simplified remarkably. The mechanical properties of the prepared HEA were enhanced by the incorporation of MHER, with the best performance obtained at 8 wt% MHER in HEA (HEA-8). Compared with the hot melt adhesive without MHER (HEA-0), the adhesion strength, tensile strength, and tensile toughness of HEA-8 attached to a stainless steel substrate were enhanced by 27.4%, 78.1%, and 475.0%, respectively. HEA-8 showed a super-high adhesion strength of approximately 10.7 MPa and outstanding reusability with >82% adhesion strength retained after five cycles. The reusability was attributed to the cleavage and formation of dynamic noncovalent quadruple hydrogen bond interactions. It is highly expected that this work will provide a facile green strategy for preparing hot melt adhesives with excellent adhesion and reusability.