Simultaneous toughening and strengthening of diglycidyl ether of bisphenol‐a using epoxy‐ended hyperbranched polymers obtained from thiol‐ene click reaction

Abstract

Epoxy‐ended hyperbranched polymers (EHBP) has become a class of additives for diglycidyl ether of bisphenol‐A (DGEBA), but it is tedious processes retards wide application. Here, we prepared EHBP by a thiol‐ene click reaction between thiol‐terminated hyperbranched polyesters and allyl glycidyl ether and modified DGEBA. The incorporation of EHBP significantly enhanced the toughness and strength of DGEBA. The mechanical properties of EHBP/DGEBA composite increased remarkably with the increasing EHBP molecular weight initially, and then decreased with further increase of EHBP molecular weight. The maximum increase of mechanical properties was observed in EHBP‐12/DGEBA composites. With increasing EHBPE‐12 content, the mechanical performance of the EHBP‐12/DGEBA composites increased firstly and plateaued at 9 wt% EHBP‐2. At 9 wt% EHBP‐12 content, the tensile strength, flexural strength and impact strength increased to 74.46 MPa, 143.58 MPa, and 39.09 kJ m−2, respectively. When loading was increased from 12 to 15 wt%, the mechanical performance started to decrease. The use of EHBP slightly decreased the thermal stability and the glass transition temperature. Protonema observed in the fracture surface can be used to explain the significant improvement in mechanical properties. POLYM. ENG. SCI., 58:1703–1709, 2018. © 2017 Society of Plastics Engineers