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Latent curing epoxy systems with reduced curing temperature and improved stability
- Zhang, Pengbo, Ali Shah, Sayyed Asim, Gao, Feng, Sun, Hao, Cui, Zhichao, Cheng, Jue, Zhang, Junying
- Thermochimica acta 2019 v.676 pp. 130-138
- adhesives, bisphenol A, curing agents, epoxides, imidazoles, molecular weight, polymers, shear strength, shelf life, temperature, tensile strength
- As a representative single component epoxy resin, diglycidyl ether of bisphenol A resin (DGEBA) is the most widely used matrix in adhesives. However, challenges are still remained including high curing temperature and short shelf life. Herein, bisphenol A (BPA), Tetrachlorobisphenol A (TCBPA), and Tetrabromobisphenol A (TBBPA) as latent curing agents and imidazole as accelerator were used in adhesives. Curing kinetics was studied by non-isothermal DSC, using a model-fitting Málek approach and a model-free advanced isoconversional method of Vyazovkin. Results indicated that curing temperature of EP-BPA, EP-TCBPA, and EP-TBBPA was reduced to 126 ℃, 94 ℃, and 106 ℃, respectively. Storage stability evaluated by DSC indicated the shelf life was up to five months. After curing, molecular weights of the as-prepared linear polymers (EP-BPA, EP-TCBPA, and EP-TBBPA) were 33,822 g/mol, 14,913 g/mol, and 18,846 g/mol, and their tensile strength and shear strength were more than 40.06 MPa and 13.64 MPa, respectively.