Synergistic toughening of epoxy resins via BPA chain extension and CTBN modification for high performance adhesive applications

To meet the demanding performance criteria of packaging materials for high-power electronic devices, this study designed a thermosetting film material with enhanced toughness, mechanical strength, and thermal resistance by synergistically modifying Diglycidyl Ether of Bisphenol A (DGEBA) epoxy resin through bisphenol A (BPA) chain extension and carboxylic acid-terminated butadiene-acrylonitrile copolymer (CTBN) toughening. Initially, the liquid epoxy resin was structurally optimized by varying the BPA content (8–30 parts per hundred resins, phr), which extended the molecular chains and reduced crosslink density. The 30 phr BPA-modified formulation demonstrated optimal performance, achieving a tensile strength of 98.69 MPa. Subsequently, CTBN (0–40 phr) was incorporated to enhance toughness further. The sample containing 30 phr CTBN (DT-30) exhibited superior mechanical properties, with a tensile strength of 99.86 MPa (a 25 % increase) and an 80 % improvement in elongation at break compared to the BPA-extended resin without CTBN. Additionally, the Al–Al lap shear strength reached 27.85 MPa, while the high-temperature char yield increased to 8.94 %, indicating enhanced thermal stability. Dynamic mechanical analysis (DMA) showed that CTBN significantly enhances toughness through nanoparticle voiding and shear yielding mechanisms, but slightly reduces the glass transition temperature (Tg). Molecular simulations revealed crack deflection in the epoxy resin and the toughening mechanism of the voiding effect. Scanning electron microscopy (SEM) confirmed that CTBN is uniformly dispersed and induces tough fracture. Rheological testing determines 133.8 °C as the optimal processing temperature. This work establishes a structure-property relationship and provides a practical strategy for designing high-performance composites through balanced BPA-CTBN modification.