Synthesis Of Novel Latent Curing Agents And Study Of Curing Property

Curing of epoxy resin could be more simple and controllable in the use of latent curing agents, the application fields of epoxy resin could be also expended in this way. In this dissertation, two novel latent curing agents of epoxy resin were synthesized via the modified dicyandiamide, furthermore, the curing study and process optimization of these two curing systems were analyzed.(1) A novel latent curing agent for epoxy resin (D-DICY) was synthesized via modifying dicyandiamide (DICY) with 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) through addition reaction. The chemical structure of D-DICY was confirmed by FTIR and 1H-NMR. The thermal properties including melting temperature and decomposition temperature of this curing agent were evaluated by DSC and TG. The study of curing process via DSC proved that the curing temperature declined 30℃ compared with the curing system of epoxy resin and dicyandiamide, which means that the expectation was reached. The optimal formula and reference curing process were also obtained. The curing system was optimized with the addition of imidazole (IMZ) as the promoter. Flame retardancy of the cured epoxy resin was analyzed by using the limit oxygen index apparatus, the result indicated that the limiting oxygen index (LOI) was improved 7.3 compared with the curing system of epoxy resin and dicyandiamide. The kinetic analysis of the curing system was studied, and the function model about storage time and temperature was also presented. Through the experimental observation, the storage time of the curing system at room temperature was more than 427 days, which proved the excellent storage stability of this curing system.(2) The other novel latent curing agent for epoxy resin (H-DICY) was synthesized via modifying dicyandiamide (DICY) with hexamethylenediamine through addition reaction. The chemical structure and properties of H-DICY were analyzed by FTIR, ’H-NMR, XRD and XPS. The study of curing process via DSC proved that the curing temperature declined nearly 80℃ compared with the curing system of epoxy resin and dicyandiamide, which means that the expectation was also reached. The optimal formula and reference curing process of these curing systems were also obtained. The curing system was optimized based on the result analysis of comparative experiments between the curing systems of H-DICY with different polymerization degrees. Through the experimental observation, the storage time of the curing system at room temperature was more than 198 days, which proved the good storage stability of the curing system.