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Hypothesis: Some adducts were prepared from three kinds of DGEBA-based epoxy resins, phthalic anhydride and an alkanol amine accelerator, as a latent accelerator for one-pot epoxy/dicy systems. These adducts come with two kinds of accelerators: DMP-30 A, which is lab-grade and Ax-10, which is industrial-grade, as well as DGEBA based epoxy resins Epikote 828, Epiran 06 and ML 504. The adduct made of Epikote 828 and DMP-30 A was considered as a reference. It seems that it might be possible to prepare a new efficient latent accelerator with change of epoxy resin and accelerator.Methods: For this purpose, four different adducts with resins and accelerators and four different epoxy/dicy mixtures with four adduct types and AX-10 accelerator and one with no adduct as a reference were prepared. Measuring the melting point, viscosity build-up versus time, gelation time, non-isothermal differential scanning calorimetry (DSC) and glass transition temperature characterization and also lap shear, interlaminar shear strength, transvers tensile and scanning electron microscope (SEM) were used to study the latent properties of the prepared adducts in the epoxy/dicy system and find its effect on mechanical properties of the final composites and all were compared with references.Findings: Melting point of all adducts is above room temperature, so they are solid at room temperature. The results show that the adducts containing the industrial accelerator in one-pot epoxy/dicy system has lower gel time at high temperature, higher viscosity changes at ambient temperature and pot life and has made no significant change in cure temperature. The mechanical properties of the composite made with an adduct consisting of ML 504 resin are accompanied by a decrease in the related values. In general, the adduct made with Epiran 06 or Epikote 828 resin and industrial accelerator is an efficient and new latent accelerator and is suitable for preparing one-pot epoxy/dicy systems.

Graphical abstract Highlights • An industrially-applicable and simple method to develop latent accelerators. • A one-pot system with at least 4 months shelf life. • This latent accelerator lowered the epoxy/dicyandiamide curing onset temperature to 130 °C. Abstract One-pot epoxy system is widely used in prepreg applications. Achieving a long storage life and at the same time, a low curing temperature is a real challenge in one-pot systems. To deal with these challenges, we developed adducts as latent accelerators for one-pot epoxy/dicyandiamide system through the addition reaction of epoxy, phthalic anhydride and different types of alkanolamine/phenol amines. Fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance spectroscopy (NMR) and thermogravimetric analysis (TGA) showed that the so-prepared adducts were long chain tertiary amines. Non-isothermal differential scanning calorimetry (DSC) proved the effectiveness of adducts towards significant reduction of the curing peak temperature of epoxy/dicyandiamide. The analysis of variance (ANOVA) revealed that the acceleration capacity is controlled by adduct ingredients of amine type, amine and phthalic anhydride content. The activation energies (E α) projected by isoconversional methods revealed different E α - conversion profiles for each system that were in agreement with chemorheological results. According to Málek method, Šesták–Berggren model was the most appropriate to fit the experimental reaction rates. Furthermore, for all one-pot epoxy/dicyandiamide samples, no viscosity build-up and epoxide group consumption were detected after 4 months indicating for their relatively long shelf lives. [ABSTRACT FROM AUTHOR]