Fecha de publicación:
22/12/2024
Fuente: Journal of applied polymer Lugar:
RESEARCH ARTICLE
Zeolitic imidazolate framework (ZIF-8) functions as a highly effective latent catalyst in the epoxy resin (A-128) and anhydride (THPA) matrix, providing excellent system stability due to its steric hindrance and solid–liquid phase separation. The curing conditions were optimized through thermodynamic analysis, and the reaction kinetics were thoroughly investigated.
Abstract
Single pack epoxy adhesives, known for their simple operation process, combined with good reactivity at moderate temperatures and excellent storage stability, have gained extensive attention. An appropriate accelerator is crucial for enhancing their performance. This study demonstrates that the zinc zeolitic imidazolate framework ZIF-8 (Zn(2-methylimidazole)2) can effectively serve as an effective accelerator for the epoxy-anhydride system, as evidenced by the complete exothermic curing curve obtained via differential scanning calorimetry (DSC) tests of the epoxy (A-128) and anhydride (THPA) adhesive sample with ZIF-8. The optimal addition amount of ZIF-8 (0.9%) was determined by assessing the glass transition temperature (T
g) of the cured resin with varying ZIF-8 weight fractions. Furthermore, the ideal curing conditions—gel temperature of 388.4 K, curing temperature of 416.7 K, and post-treatment temperature of 441.9 K—were established by analyzing heating curves at different circumstances. The epoxy (A-128) and anhydride (THPA) system with accelerator ZIF-8 exhibited superior stability compared to the commercial accelerators like PN-23 or DMP-30. This is attributed to the steric hindrance and coordination bonds of ZIF-8, indicated by a large pre-exponential factor (A
1 = 5.58 × 108) and low-value reaction rate constant (k
1 = 0.3461 × 10−3 s−1). In addition, the kinetic parameters, and an autocatalytic equation model for the epoxy (A-128) and anhydride (THPA) system with accelerator ZIF-8 have been derived through isothermal curing kinetics analysis.
