| dc.description.abstract | Polymeric materials find ubiquitous applications in modern daily life. However, as a kind of hydrocarbon-based energy-dense material, most polymeric materials are highly flammable, which is a big threat to life and property safety. With the continuously growing demand for polymeric materials in the coming years, improving their flame retardancy is becoming increasingly important. Although flame retardant chemistry has advanced since ancient times, a large portion of the periodic table has still been remained unexplored for the potential flame retardant effects, especially those transition metals. In this research, transition metal-based flame retardants were used to reduce the flammability of both natural and synthetic polymers.
Specifically, as an affordable, environmentally friendly, and energy-efficient approach, biomineralization was applied to produce TiO2 coatings on the surface of cotton fabric to form a flame retardant system. UiO-66, a common type of metal-organic framework (MOF), and its composite with SiO2 were embedded into poly (methyl methacrylate) (PMMA) via in-situ polymerization to form different composite systems. Using melt blending, ZIF-8, a commercially available type of MOF, was incorporated into a well-researched intumescent flame retardant polypropylene (PP) system to be used as a synergist to further improve its flame retardant efficiency and reduce the smoke emission. These materials were first examined using a variety of characterization tools. Their thermal decomposition behaviors were investigated using thermogravimetry (TGA). To obtain the flame retardant performance under different fire risk scenarios, their ignitability and flammability were systematically evaluated using limiting oxygen index analysis (LOI), cone calorimetry, UL-94, and microscale combustion calorimeter (MCC).
Overall, after the comprehensive evaluation under different flammability tests, those transition metal-based flame retardants used in this research demonstrate a strong flame retardant effect on both natural and synthetic polymers, even at a relatively low mass loading. They can change the thermal decomposition behaviors of polymers, promote char formation, reduce the burning intensity, and slow down the fire spread rate. Furthermore, the addition of ZIF-8 could also contribute to suppressing the smoke release and CO and CO2 production from burning intumescent flame retardant PP composites. This work provided an alternative solution to developing new environmentally friendly, non-toxic, low-leaching halogen-free flame retardants. This also gave a practical insight into the development of new and better flame retardant materials with the potential of replacing existing materials. | |
