Environmental Resistance and Fatigue Behaviors of Epoxy/Nano-Boron Nitride Thermally Conductive Structural Film Adhesive Toughened by Polyphenoxy

Abstract

The thermally conductive structural film adhesive not only carries large loads but also exhibits excellent heat-transfer performance, which has huge application prospects. Herein, a novel epoxy (Ep) thermally conductive structural film adhesive was prepared using polyphenoxy (PHO) as the toughening agent and film former, boron nitride (BN) nanosheets as the thermally conductive filler, and polyester fabric as the carrier. When the amount of PHO in the epoxy matrix was 30 phr and the content of nano-BN was 30 wt.% (Ep/PHO30/nBN30), the adhesive resin system showed good film-forming properties, thermal stability, and thermal conductivity. The glass transition temperature of Ep/PHO30/nBN30 was 215 °C, and the thermal conductivity was 209.5% higher than that of the pure epoxy resin. The Ep/PHO30/nBN30 film adhesive possessed excellent adhesion and peeling properties, and the double-lap shear strength at room temperature reached 36.69 MPa, which was 21.3% higher than that of pure epoxy resin. The double-lap shear strength reached 15.41 MPa at 150 °C, demonstrating excellent high temperature resistance. In addition, the Ep/PHO30/nBN30 film adhesive exhibited excellent heat-aging resistance, humidity, and medium resistance, and the shear strength retention rate after exposure to the complicated environment reached more than 90%. The structural film adhesive prepared showed excellent fatigue resistance in the dynamic load fatigue test, the double-lap shear strength still reached 35.55 MPa after 1,000,000 fatigue cycles, and the strength retention rate was 96.9%, showing excellent durability and fatigue resistance.

Tough Structural Adhesives with Ultra-Resistance to Both High and Cryogenic Temperature

“…As show Scheme 1 b, at room temperature, the uncured MX and MHU resins appear to be w and light-yellow solids, respectively, and they became liquid (melted) when heated about 120 °C. To confirm the structures of MX and MXU polymers, ESI-MS, 13 C-NMR, and G characterizations were performed by selecting MX-1.5 and MXU-144 as representati The combined results are given in Figure 2. The original spectra are shown in Figures S9.…”

“…The 13 C nuclear magnetic resonance ( 13 C-NMR) elucidations were performed using a Bruker AVANCE III 500 spectrometer (Bruker Corporation, Billerica, MA, USA). A total of 20 mg of solid sample was directly dissolved in 500 µL of DMSO-d6 for 13 C-NMR analysis. The observed chemical shifts were assigned by referring to the spectra of pure M-Xylylenediamine.…”

“…By modifications or reinforcement, better high-temperature adhesion strength can be achieved. For example, the thermoplastic block copolymer (TPBC) [12] and polyphenoxy (PHO) and boron nitride (BN) [13] modified epoxy resins exhibited satisfied high-temperature bonding performance at 120 and 150 • C. Polyurethane-based adhesives possess the best cryogenic adhesion property, but they generally give poor adhesion strength at high temperatures [14,15]. In addition, commercial polyurethane adhesives usually contain free N=C=O groups that are highly reactive to water, so the cure of the adhesives is affected by even a small amount of moisture [16].…”

Accelerated‐curing epoxy structural film adhesive for bonding lightweight honeycomb sandwich structures

“…Thermoplastic polymer materials are excellent toughening agents and are commonly used in the preparation of structural adhesive films. 43 Thermoplastic polymers can enhance the properties of film adhesives and improve their film-forming properties. 44 In this study, TPBC was used as a toughening agent for accelerated-curing epoxy resin systems.…”

Super-Flexibility and High-Temperature Adhesion of Epoxy Structural Adhesives Endowed by Homogeneous Rigid–Flexible Crosslinking Networks

“…However, these commercial products have poor flexibility, and the curing temperature is ordinarily higher than 100 °C. Yue et al 24 added polyphenoxy (PHO) and boron nitride (BN) into epoxy resin, and the adhesion property at 150 °C approached 15.41 MPa, whereas its glass transition temperature was as high as 215 °C, which means that it lost flexibility at RT. To the best of our knowledge, epoxy adhesive aggregate medium−low-temper- ature curing ability, excellent flexibility, and high-temperature adhesion are rarely studied until now.…”