Study on Intumescent Flame Retarded Polystyrene Composites with Improved Flame Retardancy

The flame retardancy and thermal stability of ammonium polyphosphate/tripentaerythritol (APP/TPE) intumescent flame retarded polystyrene composites (PS/IFR) combined with organically-modified layered inorganic materials (montmorillonite clay and zirconium phosphate), nanofiber (multiwall carbon nanotubs), nanoparticle (Fe2O3) and nickel catalyst were evaluated by cone calorimetry, microscale combustion calorimetry (MCC) and thermogravimetric analysis (TGA). Cone calorimetry revealed that a small substitution of IFR by most of these fillers (≤2%) imparted substantial improvement in flammability performance. The montmorillonite clay exhibited the highest efficiency in reducing the peak heat release rate of PS/IFR composite, while zirconium phosphate modified with C21H26NClO3S exhibited a negative effect. The yield and thermal stability of the char obtained from TGA correlated well with the reduction in the peak heat release rate in the cone calorimeter. Since intumesence is a condensed-phase flame process, the MCC results showed features different from those obtained from the cone calorimeter

Synergistic Effect of Carbon Nanotubes and Decabromodiphenyl Oxide/Sb\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e in Improving the Flame Retardancy of Polystyrene

Brominated flame retardant polystyrene composites were prepared by melt blending polystyrene, decabromodiphenyl oxide, antimony oxide, multi-wall carbon nanotubes and montmorillonite clay. Synergy between carbon nanotubes and clay and the brominated fire retardant was studied by thermogravimetric analysis, microscale combustion calorimetry and cone calorimetry. Nanotubes are more efficient than clay in improving the flame retardancy of the materials and promoting carbonization in the polystyrene matrix. Comparison of the results from the microscale combustion calorimeter and the cone calorimeter indicate that the rate of change of the peak heat release rate reduction in the microscale combustion calorimeter was slower than that in the cone. Both heat release capacity and reduction in the peak heat release rate in the microscale combustion calorimeter are important for screening the flame retardant materials; they show good correlations with the cone parameters, peak heat release rate and total heat released

The influence of carbon nanotubes on the combustion toxicity of PP/intumescent flame retardant composites

In recent years, carbon nanotubes (CNTs) have emerged as a promising candidate for improving the flame retardancy of polymer materials, as well as other physical properties. However, few researches have been focused on the influence of this nanoscale material on the combustion toxicity of polymer composites during combustion. In this work, the fire toxicity of polypropylene (PP) composites with intumescent flame retardants (IFRs) and CNTs has been investigated by a Purser Furnace apparatus, which is called steady state tube furnace (SSTF) and enables different fire stages to be created. The Thermo gravimetric analyzer (TGA) and derivative thermo gravimetric analysis (DTG) data indicate that the thermal stability of PP composites was increased by the addition of IFRs or CNTs. However, the SSTF results show that PP samples with IFR or CNTs or both, produced much more carbon monoxide (CO) compared to neat PP during all fire stages, resulting in a much lower CO2/CO ratio. Furthermore, an interesting finding is that the effect of CNTs on the smoke production and CxHy yield of the PP samples during the combustion changes with the combustion equivalence ratio. It indicates that the presence of CNTs promote the formation of smoke particulates from hydrocarbon, but this effect only exist when oxygen supply is not adequate. It is also concluded that the air ventilation and combustion temperature play significant roles in the fire effluent production of PP samples and the morphology of soot particulates

The influence of α-zirconium phosphate on fire performance of EVA and PS composites

Composites of polystyrene (PS) and poly(ethylene-co-vinyl acetate) (EVA) with organically modified zirconium phosphate (OZrP) were prepared by melt blending. Their morphologies were assessed by X-ray diffraction and transmission electron microscopy, while the thermal stability and flammability properties were characterized by thermogravimetric analysis and cone calorimetry. Increasing the OZrP content was not conducive to the formation of a nanostructure in EVA and poor dispersion of zirconium phosphate layers in PS at the nanometer level was observed. Increased thermal stability at high temperature and a slight reduction in peak heat release rate were found when OZrP was added to PS, while in EVA, deteriorated thermal stability and flame retardancy were observed. Unlike montmorillonite, the partial replacement of intumescent flame retardants (IFR) by 2% OZrP imparted a negative effect on the flammability of the EVA/IFR (23%)/OZrP (2%) composite, increasing the peak heat release rate of EVA/IFR (25%). The PS/IFR (18%)/OZrP (2%) composite with poly(styrene-co-maleic anhydride) (SMA) as compatibilizer exhibited better flame retardancy than PS/SMA/IFR (20%), prolonging the combustion process and increasing the time to peak heat release rate significantly. Copyright © 2011 John Wiley & Sons, Ltd

Fire Performance of Flame Retardant Polypropylene and Polystyrene Composites Screened with Microscale Combustion Calorimetry

Flame retardant polypropylene (PP) and polystyrene (PS) materials were prepared by the incorporation of decabromodiphenyl oxide and Sb2O3 in addition to nanoparticles, montmorillonite clay, and carbon nanotubes (CNTs). Their fire performance was screened with microscale combustion calorimetry (MCC) as well as evaluated by cone calorimetry. The decabromodiphenyl oxide–Sb2O3 system exhibited better efficiency in reducing the peak heat release rate (PHRR) of PP compared to PS in the MCC, whereas the trend was the opposite in cone calorimetry. Introduction of clay or CNTs to the decabromodiphenyl oxide–Sb2O3 system was beneficial in reducing the PHRR of both composites in cone calorimetry; however, a reduction in the PHRR in the MCC was only observed in the PS composites. The thermogravimetric analysis (TGA) studies revealed that the fire results from the MCC for the two types of composites were strongly correlated with their thermal degradation traces. There were poor relationships between the parameters of MCC and cone calorimetry, but good correlation between the temperature difference of the first and second peak of mass loss rate in the TGA, temperature at the PHRR in the MCC, and fire performance index in the cone calorimetry

Locus coeruleus-norepinephrine modulation of sensory processing and perception: A focused review

The locus coeruleus-norepinephrine (LC-NE) system is involved in many brain functions and neurological disorders. In this review we discuss how LC-NE signaling affects the activity of cortical and subcortical sensory neurons, and how it influences perception-driven behaviors associated with mammalian somatosensory, visual, auditory, and olfactory systems. We summarize the consistent as well as seemingly inconsistent findings across brain areas and sensory modalities and propose a framework to understand these phenomena from the perspective of adrenergic receptor expression, dose-dependent physiology and excitation-inhibition balance. We also discuss potential future research directions in this field

Three-Dimensional Superhydrophobic Hollow Hemispherical MXene for Efficient Water-in-Oil Emulsions Separation

A superhydrophobic macroporous material composed of hollow hemispherical MXene (HSMX) was synthesized by the thermal annealing of MXene-wrapped cationic polystyrene spheres (CPS@MXene). Notably, the spherical MXene shells exhibited highly efficient catalysis of the carbonization of CPS into carbon nanoparticles. Their insertion into the interlayer of MXene increased the d-spacing and created hollow hemispheres. The as-prepared HSMX with nanoscale walls had a lower packing density than MXene, but higher porosity, total pore volume, and total pore area. Moreover, the stacking of hollow hemispheres promoted the formation of a highly undulating macroporous surface and significantly improved the surface roughness of the HSMX-based 3D membrane, resulting in superhydrophobicity with a water contact angle of 156.4° and a rolling angle of 6°. As a result, the membrane exhibited good separation efficiency and Flux for emulsifier-stabilized water-in-paraffin liquid emulsions, which was dependent on its superhydrophobic performance and strong demulsification ability derived from the razor effect originating from the ultrathin walls of HSMX. This work provides a facile approach for the transformation of highly hydrophilic 2D MXene into superhydrophobic 3D HSMX, and opens a new pathway for the development of advanced MXene-based materials for environmental remediation applications

Preparation of Thermoplastic Polyester Elastomer/Cerium Carbonate Hydroxide Composites Containing Aluminum Phosphinate with Improved Flame-Retardant and Mechanical Properties

In this work, cerium carbonate hydroxide (CeCO₃OH) was synthesized by a facile sonochemical reaction. The CeCO₃OH particles were blended with thermoplastic polyester elastomer (TPEE) and aluminum phosphinate (AlP) to fabricate the fire-retardant materials. Morphology analysis results indicated that CeCO₃OH was uniformly dispersed in TPEE. Thermogravimetric analysis results demonstrated that the additives composed of CeCO₃OH and AlP led to the slight reduction of thermal decomposition temperature and maximum mass loss rate of TPEE composites. Compared with neat TPEE, all the TPEE/AlP/CeCO₃OH composites achieved the V-0 rating in Underwriters Laboratories (UL) 94 testing. Their limiting oxygen index values were also higher than those of neat TPEE and TPEE/AlP. In cone calorimetry testing, the peak heat release rate of TPEE/12AlP/3CeCO₃OH decreased from 1190 kW/m² for neat TPEE to 530 kW/m² with a reduction of 55%. Residue analysis showed that the presence of CeCO₃OH in TPEE/AlP promoted the formation of compact protective char layer resulting in the improved fire-resistant performance. The incorporation of CeCO₃OH also enhanced the tensile properties of TPEE composites

Panchromatic Light-Absorbing [70]Fullerene-Perylene-BODIPY Triad with Cascade of Energy Transfer as an Efficient Singlet Oxygen Sensitizer

A panchromatic light-absorbing [70]fullerene-perylene-BODIPY triad (C70-P-B) was synthesized and applied as a heavy atom-free organic triplet photosensitizer for photooxidation. The photophysical processes were comprehensively investigated by the methods of steady-state spectroscopy, time-resolved spectroscopy, as well as theoretical calculations. C70-P-B shows a strong absorption ability from 300–620 nm. Efficient cascading intramolecular singlet-singlet energy transfer in C70-P-B was confirmed by the luminescence study. The backward triplet excited state energy transfer from C70 moiety to perylene then occurs to populate 3perylene*. Thus, the triplet excited states of C70-P-B are distributed on both C70 and perylene moiety with lifetimes of 23 ± 1 μs and 175 ± 17 μs, respectively. C70-P-B exhibits excellent photooxidation capacity, and its yield of singlet oxygen reaches 0.82. The photooxidation rate constant of C70-P-B is 3.70 times that of C70-Boc and 1.58 times that of MB, respectively. The results in this paper are useful for designing efficient heavy atom-free organic triplet photosensitizers for practical application in photovoltaics, photodynamic therapy, etc