Catalysis, energy storage, and light harvesting require functional materials with tailored porosity and nanostructure. However, common synthesis methods that employ polymer micelles as structure-directing agents fail for zinc oxide, for cobalt oxide, and for metal carbonates in general. We report the synthesis of the oxides and carbonates of zinc, cobalt, and aluminum with micelle-templated structure. The synthesis relies on poly(ethylene oxide)-block-poly(butadiene)-block-poly(ethylene oxide) triblock copolymers and a new type of precursor formed by chemical complexation of a metal nitrate with citric acid. A general synthesis mechanism is deduced. Mechanistic insights allow for the prediction of optimal processing conditions for different oxides and carbonates based on simple thermogravimetric analysis. Employing this synthesis, films of ZnO and Co3O4 with micelle-controlled mesoporosity become accessible for the first time. It is the only soft-templating method reported so far that also yields mesoporous metal carbonates. The developed synthesis is generic in nature and can be applied to many other metal oxides and carbonates.
The pyrolysis and the flame retardancy of poly(butylene terephthalate) (PBT) containing aluminum diethylphosphinate (AlPi) and nanometric Fe2O3 were investigated using thermal analysis, evolved gas analysis (Thermogravimetry-FTIR), flammability tests (LOI, UL 94), cone calorimeter measurements and chemical analysis of residue (FTIR). AlPi mainly acts as a flame inhibitor in the gas phase, through the release of diethylphosphinic acid. A small amount of Fe2O3 in PBT promotes the formation of a carbonaceous char in the condensed phase. The combination of 5 and 8 wt% AlPi, respectively, with 2 wt% metal oxides achieves V-0 classification in the UL 94 test thanks to complementary action mechanisms. Using PBT/metal oxide nanocomposites shows a significant increase in the flame retardancy efficiency of AlPi in PBT and thus opens the route to surprisingly sufficient additive contents as low as 7 wt%.
The known flame-retardant synergism between phosphorus-based additives and metal oxides, already used for petroleum-based plastics, has been extended to bio-based materials. The pyrolysis and the flame-retardancy properties of aluminium phosphinate (AlPi) in combination with nanometric iron oxide and antimony oxide on a poly(3-hydroxy-butyrate-co-3-hydroxyvalerate)/poly(butylene adipate-co-terephthalate) (PHBV/PBAT) blend were investigated. Better fire retardancy, ascribed to increases in intermediate char, favoured improvements in the UL 94 classification. Both the phosphorus and the nanofiller components participate simultaneously in the flame-retardancy mechanism: the first acting as flame inhibition in the gas phase, and the second promoting cross-linking in the solid phase. Redox reactions between iron oxide and the phosphinate additive were confirmed by XRD analysis and provided further evidence of the activity of metal compounds.