Complexes of imidazole with poly(ethylene glycol)s as the thermal latency catalysts for epoxy–phenolic resins

Imidazole with various molecular weights poly(ethylene glycol)s, including PEG1000, PEG2000, and PEG5000, was blended and evaluated as thermal latent catalysts for the polymerization of diglycidyl ether of bisphenol A (DGEBA) under liquid–liquid or liquid–solid two phase systems. The thermal latency and storage stability properties of DGEBA resin cured by 1–5 wt% of molecular weight imidazole/PEG complexes were measured by viscometer, differential scanning calorimetry (DSC), and TGA. Based on the viscosity–shear rate results, we found the 1–3 wt% amount of imidazole/PEGs showed the better thermal latency in the thermal polymerization system. From the cure activation energy and the viscosity–storage time of these complex catalysts, the order of thermally latent activity was imidazole/PEG1000 (2) > imidazole/PEG5000 (4) > imidazole/PEG2000 (3) > imidazole. Concerning the glass transition temperature (Tg), the use of imidazole/PEG complex catalysts provided complete or near complete curing systems in the temperature range about 150 °C.

Novel imidazole/PEG complex catalysts were evaluated as thermal latent catalysts for the polymerization of diglycidyl ether of bisphenol A (DGEBA). Commercially available catalyst imidazole was used as compassion molds with imidazole/PEG complex catalysts to cure epoxy resin systems to investigate their thermal latency and storage stability. Results from the cure activation energy, the viscosity–storage time and the glass transition temperature (Tg) of the catalysts, the imidazole/PEG complex catalysts showed better thermal latency than commercialized imidazole catalyst.Figure optionsDownload as PowerPoint slideHighlights
► Complexes of imidazole with poly(ethylene glycol)s as thermal latent catalysts for epoxy-phenolic resins.
► The cured system was performed under liquid–liduid or liquid–solid two phase systems.
► The 1–3 wt% amount of imidazole/PEGs owned the better thermal latent catalyst.
► Following the cure activation energy and the viscosity–storage time studies, imidazole/PEG1000 complex provided the best thermally latent activity.