Effect of inorganic filler type and in-situ Silane modification on lap shear strength and thermal aging durability of polyamide-cured epoxy adhesive on aluminum alloy
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https://doi.org/10.54939/1859-1043.j.mst.112.2026.92-100Keywords:
Epoxy/polyamide adhesive; Inorganic filler; APTMS silane; Lap shear strength; Thermal aging.Abstract
This study investigates the effects of inorganic filler type (ZrO₂, Al, TiO₂, TiC, WC, h-BN) and in-situ silane modification (APTMS, GPTMS, VTMS) on the lap shear strength (LSS) and thermal stability of a polyamide-cured epoxy adhesive on 6061 aluminum alloy. The optimal ZrO₂ content was 5.0 wt%, yielding an initial LSS₀ of 12.4 MPa and a 500-h thermal retention factor at 80 °C (TRF-500h) of 83.1% without silane. APTMS outperformed other silanes through a dual interfacial bonding mechanism, raising the LSS₀ to 15.6 MPa and TRF-500h to 88.5% for the ZrO₂-5.0-APTMS system. Evaluation of six filler types against dual criteria (LSS₀ ≥ 15 MPa, TRF-500h ≥ 85%) identified h-BN, WC, ZrO₂, and TiC as qualifying systems. The h-BN-5.0-APTMS system achieved the best overall performance (TRF = 90.6%, LSS₅₀₀h = 14.5 MPa), driven by the unique tortuosity effect and high thermal conductivity of its lamellar structure. TGA/DTG analysis confirmed higher T₅% values for all filled systems compared to the unfilled epoxy (323 °C), following the order WC (341 °C) > BN (339 °C) > TiC (337 °C) > ZrO₂ (331 °C) > Al (329 °C) > TiO₂ (325 °C) due to the oxygen diffusion barrier effect. These results guide the development of thermally durable modified adhesives for structural applications.
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