Summary A novel compound flame retardant (carbon microspheres/magnesium hydroxide, abbreviated as CMSs/MH) was used to improve the fire performance of polyethylene terephthalate (PET). LOI, UL94, and Cone test results showed that CMSs/MH/PET composites obtained the best fire performance at the mass ratio of CMSs to MH, which was 5:5, where the CMSs/MH content was 1.0 wt. % of PET. The Py‐CS‐MS, TGA‐DSC results, and morphology of char residue revealed the flame‐retardant mechanism. CMSs/MH increased the thermal stability of PET by increasing the activation energy at the initial combustion stage. At the second stage of combustion, CMSs/MH increased the chance of recombination of free radicals and slowed the combustion. Additionally, CMSs/MH promoted the cross‐linking of pyrolysis products and further improved the continuity of the char layer. Thus, a dense and continuous char layer of CMSs/MH/PET composites was produced; this char layer reduced the heat release rate and increased the amount of char residue.

Coupling photocatalyst-coated optical fibers (P-OFs) with LEDs shows potential in environmental applications. Here we report a strategy to maximize P-OF light usage and quantify interactions between two forms of light energy (refracted light and evanescent waves) and surface-coated photocatalysts. Different TiO2-coated quartz optical fibers (TiO2-QOFs) are synthesized and characterized. An energy balance model is then developed by correlating different nano-size TiO2 coating structures with light propagation modes in TiO2-QOFs. By reducing TiO2 patchiness on optical fibers to 0.034 cm2/cm2 and increasing the average interspace distance between fiber surfaces and TiO2 coating layers to 114.3 nm, refraction is largely reduced when light is launched into TiO2-QOFs, and 91% of light propagated on the fiber surface is evanescent waves. 24% of the generated evanescent waves are not absorbed by nano-TiO2 and returned to optical fibers, thus increasing the quantum yield during degradation of a refractory pollutant (carbamazepine) in water by 32%. Our model also predicts that extending the TiO2-QOF length could fully use the returned light to double the carbamazepine degradation and quantum yield. Therefore, maximizing evanescent waves to activate photocatalysts by controlling photocatalyst coating structures emerges as an effective strategy to improve light usage in photocatalysis.

No abstract

No abstract