Improving interfacial adhesive bond durability of a structural epoxy with steel using a tannic acid‐based additive for underwater applications

Abstract

This study explores the applicability of a tannic acid‐based (TA‐AGE) additive to improve interfacial bond durability of a structural epoxy (Ep.) adhesive for underwater applications. A modified epoxy M(Ep.) was prepared from Ep. by incorporating 1 wt% (optimized) TA‐AGE additive. Although the cohesive properties of Ep. were slightly affected by the modification, underwater adhesion was improved. Incorporation of TA‐AGE additive in the adhesive can strengthen the interfacial bonds by forming more noncovalent interactions with the adherend surface. In addition, a 6‐month durability study in distilled water at 20°C, 40°C, and 60°C was performed to study the effect of water uptake on the evolution of viscoelastic, tensile properties and interfacial bond durability of Ep. and M(Ep.). With aging, the tensile properties of M(Ep.) degraded more rapidly than Ep. due to higher water uptake. Steel joints bonded with M(Ep.) in air, but cured underwater, had strength retention of 97%, 99% and 107% in 20°C, 40°C, and 60°C water, respectively, after 6‐month aging. Meanwhile, joints prepared underwater with M(Ep.) had a strength retention of 77% in 20°C water. Joint strength retention (%) in both cases was significantly higher than Ep. bonded joints aged under similar conditions.

Sustainably Sourced Tannic Acid Enables Fast-Curing High-Strength Epoxy Adhesives with Increased Toughness

“…TA/ER-3 also exhibits an average tensile shear strength of 12.2 ± 0.5 MPa and an average compressive shear strength of 34.9 ± 6.3 MPa, which is higher than those of the pure ER (Table ), suggesting enhanced tensile shear strength and compressive shear strength for TA/ER-3. The enhanced mechanical performance of TA/ER-3 is ascribed to the addition of TA with abundant phenolic hydroxyl groups, which can enhance the adhesive strength between the modified epoxy and the adhered surface through intermolecular forces such as hydrogen bonding …”

“…The enhanced mechanical performance of TA/ER-3 is ascribed to the addition of TA with abundant phenolic hydroxyl groups, which can enhance the adhesive strength between the modified epoxy and the adhered surface through intermolecular forces such as hydrogen bonding. 39 3.3. Thermal Performance of TA-Modified ERs.…”