Curing of Diglycidyl Ether of Bisphenol P with Nitro Derivatives of Amine Compounds, 1

Summary: Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and polarized light microscopy (PLM) were used to study the curing reaction of diglycidyl ether of 4,4′‐bisphenol P (DGEBP) epoxy resin with aromatic amine, 4‐nitro‐1,2‐phenylenediamine (4‐NPDA). Two exothermic peaks were observed on the DSC curves. The first peak was assigned to the curing process of DGEBP with 4‐NPDA. The second peak was associated with the decomposition that may partially be overlapped with self‐curing. Kinetic analysis was performed by using an advanced isoconversional method, which suggests that the effective activation energy for the first process is around 50 kJ · mol−1, and for the second process, it changes from 160 to 120 kJ · mol−1. The curing process (first peak on DSC curve) is associated with the formation of a liquid crystalline phase that can be converted to another mesophase on cooling if the system is not completely cured. The transition between the two mesophases becomes irreversible on further heating. DSC curves of repetitive heat‐cool cycles for DGEBP/4‐NPDA system at 10 °C · min−1. 1: heating (1′) and cooling (1) of fresh (uncured) sample; 2: heating (2′) and cooling (2) of partially cured sample; 3: heating (3′) and cooling (3) of cured sample. magnified image DSC curves of repetitive heat‐cool cycles for DGEBP/4‐NPDA system at 10 °C · min−1. 1: heating (1′) and cooling (1) of fresh (uncured) sample; 2: heating (2′) and cooling (2) of partially cured sample; 3: heating (3′) and cooling (3) of cured sample.