Search

A series of new tailored a-diimine Ni (II) complexes (Ni-OH, Ni-FOH, Ni-PhOH, and Ni-PhFOH) containing bulky ortho-N-aryl groups with various dibenzhydryl substitutes was successfully synthesized, characterized and applied in ethylene polymerization. The a-diimine ligands and Ni (II) complexes were characterized by 1H, 19F, and 13C NMR, elemental analysis, and high resolution electrospray ionization mass spectrometry (ESI-HRMS). The X-ray crystallographic study of metal complexes Ni-OH, Ni-FOH, and Ni-PhFOH revealed their distorted tetrahedral geometry. An unsymmetrical steric-enhancement design approach was employed to modulate the competition between the monomer insertion and the chain-walking process in ethylene polymerization. This facile design resulted in a high catalytic activity and yielded high molecular weight PE. The catalytic activity of these complexes was optimized by varying the polymerization conditions (temperature, time, and ethylene pressure), use of co-catalysts and variation of the Al/Ni ratio. When activated with modified methylaluminoxane (MMAO), these Ni complexes exhibited the activity as high as 29.1 × 106 g of PE (mol of Ni)−1 h−1), with a molecular weight of 1.81 × 106 g mol−1. Their thermal stability was well pronounced at elevated temperatures; high activity of 2.88 × 106 g of PE (mol of Ni)−1 h−1 and high molecular weight PE (0.86 × 106 g mol−1obtained at 90 °C). PEs with tunable branches and high melting points (127.5 °C) were obtained, which is a typical feature of LLDPE. The incorporation of fluorine atoms on N-aryl groups had a strong positive influence on the catalytic activity of the Ni complexes and favored the chain-growth process in the ethylene polymerization. Surprisingly, the simultaneous presence of terminal hydroxyl group in these complexes did not adversely affect their catalytic activity, while offering the possibility for covalent attachment to the solid supports for future heterogeneous polymerization., European Polymer Journal, 186, ISSN:0014-3057, ISSN:1873-1945

Graphene nanoplatelet (GNP) as a nanofiller improves the mechanical strength, electrical conductivity, and flame retardancy of the polymers significantly. With an increasing number of GNP-reinforced products, a careful safety assessment is needed to avoid social and economic setbacks. However, no study has addressed the effects of combustion-generated emissions from GNP-reinforced products in the lung, the most sensitive exposure route to airborne particles. Therefore, we studied the influence of GNP as a nanofiller on the emitted particles and polycyclic aromatic hydrocarbons (PAHs), and cytotoxicity of the emissions from the combustion of pure epoxy (EP) and GNP-reinforced epoxy (EP-GNP). GNP was not detected in the airborne emissions. PAHs were found in airborne particles of both emissions from EP and EP-GNP, with some differences in their concentrations. A first hazard assessment was performed on human alveolar epithelial cells exposed to the airborne emissions at air-liquid interface conditions. At 24 h and 96 h after the exposure, similar responses were observed between EP and EP-GNP except an acute transient decrease in mitochondrial activity after exposure to the emissions from EP-GNP. Both emissions from EP and EP-GNP had no acute effects on membrane integrity, cell morphology or expression of anti-oxidative stress markers (HMOX1 and SOD2 genes). Meanwhile, both emissions induced the activation of the aryl hydrocarbon receptor (CYP1A1 gene) and a transient (pro-) inflammatory response (MCP-1), but the effects between EP and EP-GNP were not significantly different., NanoImpact, 27, ISSN:2452-0748

A simple method is reported for the preparation of silver nanoparticle (AgNP) embedded pH-responsive hydrogel microparticle catalyst via Michael addition gelation and in-situ silver nitrate (AgNO3) reduction. The AgNP-hydrogel microsphere exhibited an efficient reduction of pollutants like 4-Nitrophenol (4-NP) and Congo red (CR) under acidic medium with turn over frequency (TOF) of ~170 h–1 and ~124 h–1 respectively. Interestingly, the activity of the catalysts was turned-OFF under a basic medium (≥ pH 12) due to the deswelling pH-responsive matrix surrounding the AgNPs. On the contrary, turning-OFF the hydrogenation of a cationic pollutant like methylene blue (MB) using high pH (≥ 12) was not possible, due to ionic interaction of MB molecules with the negatively charged catalyst at this pH. This feature was used to demonstrate selective hydrogenation of only MB from a mixture of 4-NP and MB. Finally, five recycling steps confirmed the reusability and practical application potential of the catalyst.

Three novel alkyl sulfone bridged phosphorus (P) compounds namely 6,6′-(sulfonylbis(ethane-2,1-diyl))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (SEDOPO), sulfonylbis(ethane-2,1-diyl))bis(diphenylphosphine oxide) (SEDPPO), and tetraphenyl (sulfonyl bis(ethane-2,1-diyl)) bis(phosphonate) (SEDPP) (i.e. phosphine oxide, phosphinate and phosphonate, respectively) were synthesized via a Michael addition reaction with good yields (≥ 85%) at a 200-g scale. They exhibited thermal stability above 250 °C, which allowed them to be melt-processed with polypropylene (PP) and formed into thin films (~ 0.6 mm). Rheological measurements of the PP blends exhibited a typical shear thinning behavior and provided evidence for the synthesized compound's thermo-oxidative stabilizing effect. This was also confirmed by thermal analysis showing that the thermo-oxidative stability of PP-SEDOPO and PP-SEDPPO blends was higher (~25 °C) than the blank PP; however, PP-SEDPP had a smaller impact. Small scale fire tests of the PP-FR blends confirmed the flame retardant efficacy of the new P-compounds. Cone calorimetry on PP-SEDOPO blends showed a reduction in the heat release rate (HRR) (~48%) compared to blank PP. Further thermal and evolved gas analysis of the PP blends confirmed that the new P-compounds are primarily active in the gas-phase.

Accidental or open waste burning and incineration of nano-enabled products (NEPs) might lead to the release of incidental nanomaterials (NMs) into the environment resulting in harmful effects on humans. We have investigated combustion-generated NM release during accidental burning for several real-life NEPs such as paints with silica (SiO2) and spruce wood panels containing SiO2 and Fe2O3 NMs, paper with SiO2 and Fe2O3 NMs and polymeric composites with CuPhthtalocyanine NMs in poly lactic acid (PLA), polyamide 6 (PA6) and thermoplastic pol-urethane (TPU) matrices.Chemical compositions, aerosols number emission factors (nefs) and concentrations of the signature elements of the NMs of the combustion-generated aerosols were investigated. In addition, the residual ash was analyzed. The outcomes of this study shed light on how NM and matrix types influenced the properties of the released aerosols. Based on our results it was established that the combustion-generated aerosols were composed of transformed NMs with modified physical-chemical characteristics compared to the pristine NMs. In addition to the transformed NMs, there were also particles due to incomplete combustion of the matrix. Types of the pristine NMs and matrices affected the characteristics of the released aerosols. Since the hazard of the aerosols is related to the inhaled aerosol number concentration, the nef is an important parameter. Our results showed that the nefs in the size range of 5.6 to 560 nm depended strongly on the type of combusted NEP, which indicated that the NEPs could be categorized according to their potential to release aerosols in this size range when they were burnt. The generated release data facilitate the assessment of human and environmental exposure and the associated risk assessment of combustion-generated aerosols from NEPs.

A simple one-pot synthesis process for functionalized mesostructured silica nanoparticles (MSNP) is reported. The novel process demonstrated the possibility to achieve MSNP with a surface area up to 501 m2.g−1 using a phosphonate based nonsilane precursor such as N, N´-bis[4,6-bis(diethylphosphono)-1,3,5-triazin-yl]-1,2-diaminoethane (ED). MSNP obtained by using 20 mol% of ED achieved a surface area of 80 m2.g−1 and increasing the ED content to 30 mol% resulted in a surface area of 501 m2.g−1. Zeta potential of novel MSNPs (−65.5 and 70.0 mV) were much higher than the nanoparticle (NP) prepared from only TEOS (−49 mV), indicating the presence of a large number of –SiOH and phosphonic acid surface functional groups, as confirmed by Fourier-transform infrared spectroscopy (FT-IR) and Nuclear magnetic resonance (NMR) analysis. The functionalized MSNPs were used as an adsorbent for the removal of cationic pollutants like methylene blue (MB). The MSNP with the highest porosity displayed favorable MB adsorption behavior with ~380 mg.g−1 of MB adsorption capacity. Facile regeneration in an acidic medium (~pH 4.5) with easy recyclability (10 cycles) confirmed the practical applicability of this novel functionalized MSNPs.

Herein, we report the industrial synthesis procedure of phosphonamidate and phosphonate derivatives via an efficient and simple chlorination of 9,10-dihydro-9-oxa-10-phosphaphenanthren-10-oxide (DO...

A facile methodology to durably modify cellulose fibers by forming in-situ phosphine oxide macromolecular physical networks is developed in this work. Such networks were formed by treating the cellulose fibers with a mixture of Michael adducts [trivinyl phosphine oxide (TVPO) and cyclic amines (piperazine and 2,4,6-tri(piperazine-1-yl)-1,3,5-triazine)] followed by a click crosslinking reaction initiated by dry heat, microwave, or steaming process. The in-situ phosphine oxide network is integrated within the cellulose fibers to produce a durable treatment against laundering. NMR and SEM analysis of the treated fibers verified the in-situ formation of phosphine oxide macromolecules in the bulk of cellulose fiber. The treatment was homogenous and achieved an outstanding phosphorus (P) retention (>95%) after even 50 laundry cycles. The treated cotton exhibited excellent fire retardant properties with a limiting oxygen index value >27% and passed the Swiss vertical flammability test at 2 wt% P. Analysis of evolved gasses during thermal decomposition of treated cellulose supported both the condensed and gas phases mechanism. The flame retardant treatment was further adapted to include antimicrobial properties by in-situ formation of silver nanoparticles within the cellulose fibers using a single-step process to demonstrate the versatility of this novel treatment methodology. The treated fabric exhibited excellent antimicrobial as well as flame retardant properties and was also durable to 50 laundry cycles. Contact angle measurements and moisture management test confirmed the excellent comfort behavior of the treated cellulose fabric.

Promising effects of DOPO-PEPA (DP), an environmental-friendly flame retardant, on the processing of polyethylene terephthalate (PET) are studied via rheological experiments. DP reveals profound melt stabilization and lubrication effects even at low concentrations (~1 wt%). Mechanical characterization of PET films confirms that the direct addition of DP powder to PET during extrusion has no adverse effects even if the films are exposed to elevated temperatures for prolonged periods. This property is particularly interesting for high-temperature applications, for instance flexible power electronics, where mechanical flexibility should not be compromised by using a melt process stabilizer.

The role of various additives (emulsifier, anti-dripping agent) and formulation procedures (pre-dispersion of solid additives in polyol via milling) which influence the flame retardancy of 6,6&prime, [ethan-1,2-diylbis(azandiyl)]bis(6H-dibenzo[c,e][1,2]oxaphosphin-6-oxid) (EDA-DOPO) containing flexible polyurethane foams has been investigated in this work. For comparison, the flame retardancy of two additional structurally-analogous bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based compounds, i.e., ethanolamine-DOPO (ETA-DOPO) and ethylene glycol-DOPO (EG-DOPO) were also evaluated together with EDA-DOPO in flexible PU foams of various formulations. The flame retardancy of these three bridged-DOPO compounds depends on the type of PU formulation. For certain PU formulations containing EDA-DOPO, lower fire performance was observed. Addition of emulsifier and polytetrafluoroethylene (PTFE) to these PU formulations influenced positively the flame retardancy of EDA-DOPO/PU foams. In addition, dispersion of EDA-DOPO and PTFE via milling in polyol improved the flame retardancy of the PU foams. Mechanistic studies performed using a microscale combustion calorimeter (MCC) and its coupling to FTIR showed no difference in the combustion efficiency of the bridged-DOPO compounds in PU foams. From MCC experiments it can be concluded that these bridged-DOPO compounds and their decomposition products may work primarily in the gas phase as flame inhibitors. The physiochemical behavior of additives in PU formulation responsible for the improvement in the flame retardancy of PU foams was further investigated by studying the dripping behavior of the PU foams in the UL 94 HB test. A high-speed camera was used to study the dripping behavior in the UL 94 HB test and results indicate a considerable reduction of the total number of melt drips and flaming drips for the flame retardant formulations. This reduction in melt drips and flaming drips during the UL 94 HB tests help PU foams achieve higher fire classification.

This study addresses three very important aspects of sustainable development of new flame re-tardant material, i.e. in situ solvent free synthesis of flame retardant macromolecules during thermal processing of polymers, their leaching behavior from the polymer matrix and their preliminary toxicity assessment. Polyamide 6 (PA6) was functionalized by a novel reactive extrusion process. In situ synthesis of phosphine oxide based macromolecules was obtained via Michael addition reaction of divinyl phenyl phosphine oxide (DVPPO) and piperazine during the reactive extrusion process. The formation of phosphine oxide macromolecules (oligomers and low molecular weight polymers) were confirmed by NMR study of the modified PA6 polymer and UPLC-MS analysis of extracts from PA6 samples. Elemental analysis of the modified PA6 after the extraction with chloroform and water confirmed retention of majority of phosphorus species, confirming the beneficial effect of large macromolecular additives. This non-leaching behavior of modified PA6 is an important requirement for thin walled substrates like fibers and films where long-term durability is very important. The reactive extruded PA6 was successfully processed into textile fibers via melt spinning process in a laboratory spinning plant. The presence of phosphine oxide macromolecules in PA6 matrix had a lubricating effect, which has influence in the thermal processing and final properties of the fiber. The modified PA6 was evaluated for fire performance in small-scale fire tests where it showed improved fire performance. Moreover, the preliminary toxicity assessment of the relatively unknown DVPPO, via a well-established in vitro platform showed no adverse effects on cell viability.

Cellulose fibers are promoted for use in various textile applications due their sustainable nature. Cellulose-based fibers vary considerably in their mechanical and flammability properties depending on their chemical composition. The chemical composition of a cellulose-based fiber is further dependent on their source (i.e., seed, leaf, cane, fruit, wood, bast, and grass). Being organic in nature, cellulose fibers, and their products thereof, pose considerable fire risk. In this work we have compared the flammability properties of cellulose fibers obtained from two different sources (i.e., cotton and peat). Compared to cotton cellulose textiles, peat-based cellulose textiles burn longer with a prominent afterglow which can be attributed to the presence of lignin in its structure. A series of phosphoramidates were synthesized and applied on both cellulose textiles. From thermogravimetric and pyrolysis combustion flow analysis of the treated cellulose, we were able to relate the flame retardant efficacy of the synthesized phosphorus compounds to their chemical structure. The phosphoramidates with methyl phosphoester groups exhibited higher condensed phase flame retardant effects on both types of cellulose textiles investigated in this study. In addition, the bis-phosphoramidates exhibited higher flame retardant efficacy compared to the mono-phosphoramidates.