No abstract

In this article, an efficient and simple approach for the preparation of organic-inorganic intumescent interfacial flame retardants, aiming at enhancing the flame-retardant efficiency and interfacial adhesion between matrix and flame retardants was presented. The expandable graphite (EG) was functionalized by using a grafting process containing phosphorous, resulting in the formation of organic-inorganic intumescent flame retardants. Based on the successful grafting reaction, a series of flame-retardant polypropylene (PP) composites with different content of modified EG (MEG) were prepared and evaluated. With the incorporation of 30 wt% of MEG into PP, the satisfactory UL-94 flame retardant grade (V-0) and limiting oxygen index (LOI) as high as 25.3% were obtained. The residues of the PP/MEG composites were significantly increased with PP/EG and PP/EG/DOPO composites. Moreover, the residual char of PP/MEG composites is more compact and integrated. In addition, the formation of organic side chains on the MEG surface by the grafting reaction also contributed to an improvement in the interfacial compatibility, leading to an enhancement in mechanical properties of the composites compared with the PP composites filled with EG. The interfacial grafting flame retardants provided a novel way to prepare organic-inorganic intumescent flame retardants and the as-prepared flame retardants exhibited excellent flame retardant efficiency.

In this work, the flame‐retardant high‐density polyethylene/ethylene vinyl‐acetate copolymer (HDPE/EVA) composites have been prepared by using expandable graphite (EG) as a flame retardant combined with ammonium polyphosphate (APP) and red phosphorus masterbatch (RPM) as synergists. The synergistic effects of these additives on the flammability behaviors of the filled composites have been investigated by limiting oxygen index, UL‐94 test, cone calorimeter test, thermogravimetric analysis (TGA), Fourier‐transform infrared (FTIR), and scanning electron microscopy. The results show that APP and RPM are good synergists for improving the flame retardancy of EG‐filled HDPE/EVA composites. The data from TGA and FTIR spectra also indicate the synergistic effects of APP and RPM with EG considerably enhance the thermal degradation temperatures but decrease the charred residues of the HDPE/EVA/EG composites because the flame‐retardant mechanism has changed. The morphological observations present positive evidences that the synergistic effects take place in APP and RPM with EG in flame‐retardant EG‐filled HDPE/EVA/EG composites. The formation of stable and compact charred residues promoted by APP and RPM with EG acts as effective heat barriers and thermal insulations, which improves the flame‐retardant performances and prevents the underlying polymer materials from burning. Copyright © 2015 John Wiley & Sons, Ltd.

Herein, a one‐step solvothermal method that shows incorporation of the graphene quantum dots (GQDs) on Fe‐based metal organic frameworks (MOFs) [MIL‐101(Fe)] to form GQD/MIL‐101(Fe) (G/M101) composites is reported. MIL‐101(Fe) with the sensitization of GQDs could significantly improve the photocatalytic reduction efficiency of CO2 to generate CO. The prepared composites exhibit excellent optical properties and the photocatalytic activity of G/M101 composites is relevant to GQDs ratio. The CO production rate over G/M101‐5% (224.71 µmol h−1 g−1) is 5 times higher than that of MIL‐101(Fe) (46.20 µmol h−1 g−1). The promising photocatalytic activity of G/M101‐5% strongly depends on the beneficial separation and transfer of photoinduced carriers via a charge migration between GQDs and MIL‐101(Fe). The microstructures and interfacial structures of the G/M101‐5% composite demonstrate that GQDs are closely loaded on the surface of MIL‐101 (Fe), and thus favors to the photoreduction according to their sp2 bonding. This work may figure a new way for the synthesis of photocatalysts for the application on carbon stabilization.