Interplay between rheological and structural evolution of benzoxazine resins during polymerization

The main aim of this work is to study the influence of different polymerization temperatures on the polymerization processes of phenol/diaminodiphenylmethane (P-ddm)-based benzoxazines. Small amplitude oscillatory shear (SAOS), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) are used, and the results reveal the evolution of the rheological behavior of benzoxazine resins during polymerization. Tan δ clearly shows two peaks at lower temperatures and one of them at elevated temperatures. The first low-temperature peak is the ring-opening and the temporary structure of intermolecular hydrogen-bonding, while the second peak, which is much less outstanding in magnitude at higher temperatures, is the actual buildup of a molecular network.