Thermal Oxidation Behavior and Mechanisms for Silicon-Containing Arylacetylene Resins: Experimental and Reactive Force Field Molecular Dynamics Simulations

Silicon-containing arylacetylene resins (PSAs) are widely used as heat-resistant resin matrices in aerospace and electronic information technology. In this paper, the thermal oxidation behavior and its mechanism for cured poly(diethynylbenzene-dimethylsilylene-3,6-diethynylcarbazole) (DEC-DMS) were investigated via experiments and simulations. The macroscopic thermal oxidation kinetics of cured DEC-DMS were studied via thermogravimetric analysis (TGA), and the reaction steps were analyzed via mathematical deconvolution. The structural changes in the thermal oxidation residues formed at different thermal oxidation temperatures were characterized by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The composition of the volatile products generated during thermal oxidation of the cured DEC-DMS was detected online via thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR). The thermal oxidation of cured DEC-DMS was simulated via reactive force field molecular dynamics (ReaxFF-MD), and possible thermal oxidation reaction pathways and volatile matter production pathways were analyzed. The results showed that the thermal oxidation of cured DEC-DMS involved three steps: (1) thermal oxidation and weight gain of unsaturated bonds, (2) oxidative cleavage of side chain groups, and (3) oxidative degradation of cross-links and aromatic rings. The oxidative degradation products included CO, CO 2, CH 4, and H 2 O. The results provide theoretical guidance for the development of PSAs resistant to thermal oxidation.