Preparation of microencapsulated physicochemical composite retardant and study of the flame retardant mechanism

In order to solve the shortcomings of traditional inhibitors, which are easy to be interfered by the outside world during the inhibition process and the active ingredients are easy to be oxidized and invalidated, micro- encapsulated inhibitors were developed. In this study, we prepared microencapsulated inhibitors of varying wall- to-core ratios using a composite phase of polyethylene glycol 20,000 (PEG-20000) and octenyl amyl succinate (OSAS) as the wall material and a lauryl glucoside (APG-12) and butyl hydroxyanisole (BHA) phase as the core material. After thoroughly mixing the microcapsule inhibitor with coal samples, simultaneous thermal analyzer (TG/DSC) and a temperature-programmed system were used to evaluate the resisting qualities of the produced microencapsulated inhibitors. The results of the temperature programmed experiment showed that the overall CO release from the blocked coal samples was less than that of the original coal. According to thermogravimetric results, the most effective inhibition occurred when the wall/core ratio of the microcapsule inhibitor was 4:1. This also resulted in a reduction of the maximum coal weight loss rate from 1.34 to 0.96 %/min and an increase in the maximum coal weight loss temperature from 477.4 to 507.6 degrees C. The microencapsulated inhibitor melts in the wall at 57.4 degrees C, enabling temperature-sensitive intelligent control of core release. Following heating the raw and inhibited coal samples to 100 and 200 degrees C, respectively, Fourier infrared spectroscopy was conducted. At these temperatures, the amounts of ether bonds increased by 20.4 and 22.6 %, and the number of free hydroxyl groups decreased by 12.8 and 2.7 %, respectively, in the inhibited coal samples. Finally, molecular dynamics theory was applied to investigate the inhibitory mechanism. The prepared microcapsule retardant effectively inhibited the spontaneous combustion reaction of coal, suggesting this microcapsule inhibitor could be manufactured as a novel inhibitor for coal spontaneous combustion.