Ningning Hong

Effect of Cellulose Acetate Butyrate Microencapsulated Ammonium Polyphosphate on the Flame Retardancy, Mechanical, Electrical, and Thermal Properties of Intumescent Flame-Retardant Ethylene–Vinyl Acetate Copolymer/Microencapsulated Ammonium Polyphosphate/Polyamide-6 Blends

Ammonium polyphosphate (APP), a widely used intumescent flame retardant, has been microencapsulated by cellulose acetate butyrate with the aim of enhancing the water resistance of APP and the compatibility between the ethylene-vinyl acetate copolymer (EVA) matrix and APP. The structure of microencapsulated ammonium polyphosphate (MCAPP) was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and water contact angle (WCA). The flame retadancy and thermal stability were investigated by a limiting oxygen index (LOI) test, UL-94 test, cone calorimeter, and thermogravimetric analysis (TGA). The WCA results indicated that MCAPP has excellent water resistance and hydrophobicity. The results demonstrated that MCAPP enhanced interfacial adhesion, mechanical, electrical, and thermal stability of the EVA/MCAPP/polyamide-6 (PA-6) system. The microencapsulation not only imparted EVA/MCAPP/PA-6 with a higher LOI value and UL-94 rating but also could significantly improve the fire safety. Furthermore, the microencapsulated EVA/MCAPP/PA-6 composites can still pass the UL-94 V-0 rating after treatment with water for 3 days at 70 °C, indicating excellent water resistance. This investigation provides a promising formulation for the intumescent flame retardant EVA with excellent properties.

Influence of g-C3N4 nanosheets on thermal stability and mechanical properties of biopolymer electrolyte nanocomposite films: a novel investigation.

A series of sodium alginate (SA) nanocomposite films with different loading levels of graphitic-like carbon nitride (g-C3N4) were fabricated via the casting technique. The structure and morphology of nanocomposite films were investigated by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Thermogravimetric analysis results suggested that thermal stability of all the nanocomposite films was enhanced significantly, including initial thermal degradation temperature increased by 29.1 °C and half thermal degradation temperature improved by 118.2 °C. Mechanical properties characterized by tensile testing and dynamic mechanical analysis measurements were also reinforced remarkably. With addition of 6.0 wt % g-C3N4, the tensile strength of SA nanocomposite films was dramatically enhanced by 103%, while the Youngs modulus remarkably increased from 60 to 3540 MPa. Moreover, the storage modulus significantly improved by 34.5% was observed at loadings as low as 2.0 wt %. These enhancements were further investigated by means of differential scanning calorimetry and real time Fourier transform infrared spectra. A new perspective of balance was proposed to explain the improvement of those properties for the first time. At lower than 1.0 wt % loading, most of the g-C3N4 nanosheets were discrete in the SA matrix, resulting in improved thermal stability and mechanical properties; above 1.0 wt % and below 6.0 wt % content, the aggregation was present in SA host coupled with insufficient hydrogen bondings limiting the barrier for heat and leading to the earlier degradation and poor dispersion; at 6.0 wt % addition, the favorable balance was established with enhanced thermal and mechanical performances. However, the balance point of 2.0 wt % from dynamic mechanical analysis was due to combination of temperature and agglomeration. The work may contribute to a potential research approach for other nanocomposites.

Fabrication of graphene/Ni–Ce mixed oxide with excellent performance for reducing fire hazard of polypropylene

A hybrid graphene/Ni–Ce mixed oxide (Gs–NiCexOy) was facilely fabricated using a co-precipitation and subsequent calcination route. Ni–Ce mixed oxide nanoparticles with a uniform diameter of 10–15 nm were assembled on the graphene nanosheets, as demonstrated by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Subsequently, the Gs–NiCexOy hybrid was applied to reduce the fire hazards of polypropylene (PP). It was found that the thermal stability of PP composite was obviously enhanced upon the incorporation of 2.5 wt% Gs–NiCexOy. Furthermore, the addition of Gs–NiCexOy significantly improved the fire safety of PP composite, as evidenced by the dramaticl reduction of peak heat release rate, total heat release, smoke production rate, total smoke production and CO production rate. The total flammable gaseous products from the PP composite were decreased and residual char was increased with the addition of Gs–NiCexOy. The flame retardant mechanism was attributed to the combined effect of the physical barrier of graphene nanosheets and the high catalytic activity of t he Ni–Ce mixed oxide. This work could allow opening the door to a future potent graphene based nanomaterial in the domain of risk.

Effect of Graphene on the Fire and Mechanical Performances of Glass Fiber-Reinforced Polyamide 6 Composites Containing Aluminum Hypophosphite

The effect of graphene nanosheets (GNS) on the fire and mechanical performances of glass fiber-reinforced polyamide 6 composites containing aluminum hypophosphite (GFPA6) was investigated. Results indicated that the introduction of GNS played little role in improving the thermal stability and fire retardancy of the GFPA6 composite, but exhibited visible anti-dripping phenomenon performance. With the addition of GNS, the mechanical properties of the composite are obviously increased. When the content of GNS was 1 wt.%, the composite had the optimized mechanical properties with tensile strength of 52 Mpa, bending strength of 66 Mpa, and impact strength of 15 KJ/m2, respectively.

Flame-retardant and Anti-dripping Properties of Intumescent Flame-retardant Polylactide with Different Synergists

The flame-retardant and anti-dripping properties of biodegradable polylactide (PLA) materials during the combustion process were improved using intumescent flame-retardant (IFR) and different synergists. Organophilic montmorillonite (OMT), zinc borate (ZB), fumed silica (FS), tetraethoxysilane (TEOS) and polytetrafluoroethylene (PTFE) were chosen as the anti-dripping synergists for IFR in flame-retardant PLA. The flammability properties and thermal stability of PLA composites were investigated with UL-94, limiting oxygen index (LOI), thermogravimetric analysis (TGA), melt flow index (MFI), etc. It is found that OMT and ZB are the best anti-dripping synergists for IFR PLA. The anti-dripping mechanisms of all the additives are discussed.

Integrated effect of supramolecular self-assembled sandwich-like melamine cyanurate/MoS2 hybrid sheets on reducing fire hazards of polyamide 6 composites

A novel strategy of using supramolecular self-assembly for preparing sandwich-like melamine cyanurate/MoS2 sheets as the hybrid flame retardants for polyamide 6 (PA6) is reported for the first time. The introduction of MoS2 sheets function not only as a template to induce the formation of two-dimensional melamine cyanurate capping layers but also as a synergist to generate integrated flame-retarding effect of hybrid sheets, as well as a high-performance smoke suppressor to reduce fire hazards of PA6 materials. Once incorporating this well-designed structures (4wt%) into PA6 matrix, there resulted in a remarkable drop (40%) in the peak heat release rate and a 25% reduction in total heat release. Moreover, the smoke production and pyrolysis gaseous products were efficiently suppressed by the addition of sandwich-like hybrid sheets. The integrated functions consisting of inherent flame retarding effect, physical barrier performance and catalytic activity are believed to the crucial guarantee for the reduced fire hazards of PA6 nanocomposites. Furthermore, this novel strategy with facile and scalable features may provide reference for developing various kinds of MoS2 based hybrid sheets for diverse applications.

Ultrathin Beta-Nickel hydroxide nanosheets grown along multi-walled carbon nanotubes: A novel nanohybrid for enhancing flame retardancy and smoke toxicity suppression of unsaturated polyester resin

Novel nanohybrid (β-Ni(OH)2-CNTs) obtained by ultrathin Beta-Nickel hydroxide (β-Ni(OH)2) nanosheets grown along multi-walled carbon nanotubes (CNTs) was successfully synthesized and then incorporated into UPR to prepare UPR/β-Ni(OH)2-CNTs nanocomposites. Structure of β-Ni(OH)2-CNTs nanohybrid was confirmed by X-ray diffraction, scanning electron microscopy measurements. Compared with single CNTs or β-Ni(OH)2, the dispersion of β-Ni(OH)2-CNTs in UPR was improved greatly. And the UPR/β-Ni(OH)2-CNTs nanocomposites exhibited significant improvements in flame retardancy, smoke suppression, and mechanical properties, including decreased peak heat release rate by 39.79%, decreased total heat release by 44.87%, decreased smoke release rate by 29.86%, and increased tensile strength by 12.1%. Moreover, the amount of toxic volatile from UPR nanocomposites decomposition was dramatically reduced, and smoke generation was effectively inhibited during combustion. The dramatical reduction of fire hazards can be ascribed to the good dispersion, the catalytic charring effect of β-Ni(OH)2 nanosheets and physical barrier effect of stable network structure consisted of β-Ni(OH)2 and CNTs.

Significant Removal of Harmful Compounds in Mainstream Cigarette Smoke Using Carbon Nanotubes Mixture Prepared by Catalytic Pyrolysis

Carbon nanotubes mixture (CNTM), synthesized by the pyrolysis of polypropylene (PP)/organically modified montmorillonite (OMMT) nanocomposites catalyzed by Ni2O3, was used as a filter additive to remove harmful compounds in mainstream cigarette smoke. CNTM is mainly composed of carbon nanotubes (CNTs) with a little amount of amorphous carbon, Ni element and the thermal degradation residue of OMMT. The textural structure of CNTM has mesoporous and macroporous nanostructures. After introducing 15 mg of CNTM into cigarette filter, some of the most important harmful compounds including tar, nicotine, benzo[a]pyrene (B[a]P) and phenolic compounds were more efficiently adsorbed in comparison with using commercial activated carbon, which can be related to the relatively bigger pore volume and a geometric confinement of CNT in CNTM for some toxic compounds in cigarette smoke. In particular, CNTs have a strong chemisorption capacity for B[a]P or phenolic compounds due to the π–π interactions between benzene rings.

Thermal decomposition of polypropylene by tunable synchrotron vacuum ultraviolet photoionization mass spectrometry

The application of synchrotron vacuum ultraviolet (VUV) photoionization combined with molecular-beam mass spectrometry, also called synchrotron VUV photoionization mass spectrometry (SVUV-PIMS), in the research of the thermal decomposition of polypropylene (PP) was studied, and some main pyrolysis products formed at different photon energies have been identified. Using SVUV-PIMS, some isomers can be distinguished, which are much helpful for further understanding of the thermal decomposition of PP.

The growth mechanism of multi-wall carbon nanotubes produced by pyrolyzing polypropylene composite

The growth mechanism of multi-wall carbon nanotubes (MWCNTs) produced by pyrolyzing polypropylene composite were studied. Scanning electron microscopy, transmission electron microscopy and high resolution electron microscopy (HRTEM) were employed to demonstrate that the charred residue formed from PP/organically modified montmorillonite/nickel oxide (Ni2O3) composite contains an abundance of MWCNTs with almost homogeneous distribution of diameters. X-ray diffraction and HRTEM reveals that a real active site for the growth of MWCNTs is Ni not Ni2O3. Meanwhile, the growth mechanism described as the yarmulke mechanism is proposed based on the experimental analysis.