Nana Tian

Synthesis and characterization of a novel organophosphorus oligomer and its application in improving flame retardancy of epoxy resin

A novel organophosphorus, poly(4,4-dihydroxy-1-methyl-ethyl diphenol-o-bicyclic pentaerythritol phosphatephosphate) (PCPBO), was synthesized and characterized by FTIR, 1H NMR and 31P NMR. The flame retardancy and thermal stability of epoxy resin with different PCPBO loadings were investigated using the limited oxygen index (LOI), vertical burning test, cone calorimeter test and thermogravimetric analysis. The results showed that the incorporation of PCPBO into epoxy resin (EP) significantly improved its flame retardancy and thermal stability. The reduction of the peak heat release rate, total heat release and the increased char yield at high temperature further confirmed the improvement of the flame retardancy. FT-IR at different temperatures and the scanning electron microscopy of residual char revealed that the addition of PCPBO could induce the formation of an intumescent char layer, which retarded the degradation and combustion process of EP.

Striking influence of Fe2O3 on the “catalytic carbonization” of chlorinated poly(vinyl chloride) into carbon microspheres with high performance in the photo-degradation of Congo red

A one-pot approach was demonstrated to effectively synthesize carbon microspheres through “catalytic carbonization” of commercial chlorinated poly(vinyl chloride) (CPVC) microspheres by Fe2O3 at 700 °C. Without Fe2O3, a “sponge-like” carbon lump was obtained. However, after adding Fe2O3 (even 0.5 g per 100 g CPVC) into CPVC, carbon microspheres with octahedral Fe3O4 microcrystals uniformly embedded on the surface (Fe/CMS) were synthesized. The influence of Fe2O3 on the carbonization of CPVC microspheres was investigated. It was found that Fe2O3 significantly accelerated the dehydrochlorination of CPVC into polyene before the melting of the CPVC microsphere surface. As a result, the microspheres of raw CPVC showed a “shape-duplicate” carbonization behaviour. The resultant Fe/CMS showed high photo-degradation efficiency of Congo red under UV irradiation via a heterogeneous photo-Fenton process with high recyclablity, reusability and long-term stability. This indicated that the resultant Fe/CMS has a potential application in wastewater treatment. Therefore, the initial catalytic substance could be effectively used as a catalyst twice in the carbonization of CPVC microspheres and in the subsequent application of Fe/CMS. More importantly, the strategy of “catalytic carbonization” offers a new potential way to largely convert charring polymers into functional carbon and carbon-based materials with various morphologies.

Flammability properties and electromagnetic interference shielding of PVC/graphene composites containing Fe3O4 nanoparticles

The effects of combined graphene/Fe3O4 nanoparticles on the flame retardancy and smoke suppression of PVC were studied. The dispersion state of graphene in the PVC matrix was improved with the help of Fe3O4 nanoparticles. As a result, the peak values of heat release rate and smoke production rate measured by cone calorimetry were obviously decreased in the PVC/graphene/Fe3O4 composites. According to the results from TGA tests and structural characterization of residual char, the improved flame retardancy was partially attributed to the formation of a network-like structure due to the good dispersion state of graphene in the PVC matrix, and partially to the carbonization of degradation products of PVC catalyzed by Fe3O4 nanoparticles. In addition, ternary PVC composites showed higher mechanical properties than pure PVC. More importantly, the resulting material possessed both electrical and magnetic properties. As a result, the ternary composites showed favorable electromagnetic shielding efficiency in the X-band frequency region (8–12 GHz), due to the formation of conducting interconnected graphene-based networks in the insulating PVC matrix and the magnetic properties.

Nanosized carbon black combined with Ni2O3 as "universal" catalysts for synergistically catalyzing carbonization of polyolefin wastes to synthesize carbon nanotubes and application for supercapacitors.

The catalytic carbonization of polyolefin materials to synthesize carbon nanotubes (CNTs) is a promising strategy for the processing and recycling of plastic wastes, but this approach is generally limited due to the selectivity of catalysts and the difficulties in separating the polyolefin mixture. In this study, the influence of nanosized carbon black (CB) and Ni2O3 as a novel combined catalyst system on catalyzing carbonization of polypropylene (PP), polyethylene (PE), polystyrene (PS) and their blends was investigated. We showed that this combination was efficient to promote the carbonization of these polymers to produce CNTs with high yields and of good quality. Catalytic pyrolysis and model carbonization experiments indicated that the carbonization mechanism was attributed to the synergistic effect of the combined catalysts rendered by CB and Ni2O3: CB catalyzed the degradation of PP, PE, and PS to selectively produce more aromatic compounds, which were subsequently dehydrogenated and reassembled into CNTs via the catalytic action of CB together with Ni particles. Moreover, the performance of the synthesized CNTs as the electrode of supercapacitor was investigated. The supercapacitor displayed a high specific capacitance as compared to supercapacitors using commercial CNTs and CB. This difference was attributed to the relatively larger specific surface areas of our synthetic CNTs and their more oxygen-containing groups.

Upcycle waste plastics to magnetic carbon materials for dye adsorption from polluted water

Here, we report an efficient method for the transformation of waste car bumpers into mesoporous magnetic carbon material. Nearly 25 wt% of polypropylene was transformed into carbon material when an optimized amount of catalysts was introduced into the bumper composite. In addition, due to the presence of Fe and Co nanoparticles, the carbon nanomaterial exhibits magnetic properties. The obtained product was used as an effective adsorbent for the removal of dye pollutants from water – nearly 100% of rhodamine B (RhB) and methylene blue (MB) can be efficiently removed from an aqueous solution in a short duration. Furthermore, benefiting from their strong saturation magnetization, the obtained carbon materials can be easily separated from the solution by a magnet and reused multiple times. Based on the experimental results, the proposed route can pave a way to recycle waste plastics to provide large amounts of highly valuable carbon products in the future.

Simultaneously improving the mechanical properties and flame retardancy of polypropylene using functionalized carbon nanotubes by covalently wrapping flame retardants followed by linking polypropylene

The fabrication of polymer nanocomposites with improved physical and chemical properties is a hot topic in the fields of materials and chemistry. In this work, carbon nanotubes (CNTs) are functionalized through flame retardant wrapping and maleic anhydride polypropylene (PPMA) covalently attaching to achieve a compact char layer and strong interfacial adhesion. The resultant polypropylene (PP)/functionalized CNT (FCNT) composites show remarkably improved flame retardancy and mechanical properties. For example, with the incorporation of FCNTs, the mechanical properties of PP are largely improved, meanwhile the ductility is maintained. This is thanks to the strong interfacial adhesion between FCNTs and the PP matrix. In contrast, the elongation at break of the PP/CNT composites decreases seriously. More importantly, the flame retardancy of the PP/FCNT composites is much better than that of PP and the PP/CNT composites. The improved flame retardancy results from the fact that the flame retardant wrapping forms a char layer on the surface of the CNTs, which protects the CNTs from being destroyed during combustion. As a result, the quality of the residual char is improved. The flammability of the PP composites is strongly dependent on the residual char of the CNTs. The compact and continuous residual char of the FCNTs not only acts as the shield for heat transfer, but also hinders the migration of volatile decomposition products out of PP and the diffusion of oxygen into PP.