Effects of corona discharge on the surface structure, morphology and properties of multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were modified by corona discharge and then heat treated in the air. The influences of corona discharge parameters such as treatment time and processing power were investigated. The results of energy dispersive X-ray analysis (EDX) and thermogravimetric analysis (TGA) indicated the introduction of oxygen-containing functional groups onto the surface of the MWCNTs after heat treatment. The water contact angle tests showed that the hydrophobicity of the MWCNTs was decreased to some extent. The static water contact angle was reduced from 146° to 122° when the time of the corona discharge treatment reached 3 min at the processing power of 200 W. The enhanced thermomechanical and mechanical properties of epoxy nanocomposites filled with the corona discharge treated MWCNTs were observed. The modified MWCNTs conferred better properties on the composites than the pristine MWCNTs because of the improved dispersion of MWCNTs in matrix and the enhanced interfacial interaction between the treated MWCNTs and epoxy

Surface-initiated graft polymerization on multiwalled carbon nanotubes pretreated by corona discharge at atmospheric pressure

Surface-initiated graft polymerization on multi-walled carbon nanotubes pretreated with a corona discharge at atmospheric pressure was explored. The mechanism of the corona-discharge-induced graft polymerization is discussed. The results indicate that MWCNTs were encapsulated by poly(glycidyl methacrylate) (PGMA), demonstrating the formation of PGMA-grafted MWCNTs (PGMA-g-MWCNTs), with a grafting ratio of about 22 wt%. The solubility of PGMA-g-MWCNTs in ethanol was dramatically improved compared to pristine MWCNTs, which could contribute to fabricating high-performance polymer/MWCNTs nanocomposites in the future. Compared with most plasma processes, which operate at low pressures, corona discharge has the merit of working at atmospheric pressure

Thermal degradation and flammability properties of HDPE/EVA/C60 nanocomposites

The thermal and flameretardancy properties of high-density polyethylene (HDPE)/ethylene vinyl-acetate copolymer (EVA)/fullerene (C60) nanocomposites were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and cone calorimetry with C60 loading varied from 0.5 to 2% by mass fraction. Dispersion of C60 in HDPE/EVA blend was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). TGA and DSC results showed that the presence of C60 could remarkably enhance the thermal stability, and cone calorimeter measurements indicated that incorporating C60 could result in a significant reduction in the peak heat release rate and a much longer time to ignition of the HDPE/EVA blend. Furthermore, the larger the C60 loading level, the better the flame retardancy of HDPE/EVA/C60 nanocomposites

Effects of reactive compatibilization on the morphological, thermal, mechanical and rheological properties of intumescent flame retarded polypropylene

Flame-retardant polypropylene (PP) samples were in situ compatibilized with maleic anhydride grafted PP. Compatibilization reaction was verified by an IR spectrum and gel content measurements. Electron microscopy images showed that compatibilization could considerably reduce the size of the flame-retardant domains, control the phase morphology, and improve the interfacial adhesion between PP and intumescent flame retardant (IFR) with different IFR loading levels. The limiting oxygen index (LOI) of flame-retardant PP increased to different extents after compatibilization, indicating an improvement in the flame retardancy. Compatibilization enhanced the thermal stability to some extent and remarkably delayed thermal oxidative degradation of flame-retardant PP. For PP containing 20 wt % flame retardant, the temperature at which the maximum weight loss rate occurred was enhanced by about 99 °C after compatibilization. The storage modulus and glass transition temperatures were elevated to different extents. Tensile strengths of samples reduced in the presence of flame retardant alone but in the additional presence of compatibilizer were restored to levels similar to those of pure PP. Elongation-at-break values, however, showed IFR concentration-dependent reductions that were less for compatibilized samples. Furthermore, the complex viscosity of a compatibilized PP melt turned slightly smaller, which is favorable to melt processing

Manganoan skarn in the Shizhuyuan polymetallic tungsten deposit, Hunan Province

International audienceA manganoan skarn in the ShizhuyQan supergiant W-Sn-MO-Bi-Be deposit is sixdied i n the present papzr. I t co~sistosf spessartine, almandi~ic-spessartinic garnet, rhodonite, tephroite, helvite, alabandine, Mo-bearing salite, Mn-rich hedenbergite, &In-rich phlogopite and rhodochrosite and spacio-temporally develops together with the greisenization and releva~t mineralizai-ions after calcic skarnization and retrograde alteration. From proximal to distal contact zones, its mineral assemblages become incseasi~glyc omplicated and the manganese content of their varicras minerals is getting higher and higher. The complicated mineral assemblages of the manganoax skarrr and their spaciotemporal distribution apparently prove the evolutional direction of the skarn in the Shizhuyuan polymet allic tungsten deposit

Serological ferritin, 100A12, procalcitonin and APACHEII score in prediction the prognosis of acute respiratory distress syndrome

Objective The aim of the present work was to investigate the prognostic value of serological ferritin, 100A12, procalcitonin (PCT) and APACHEII score in predicting death risk for patients with acute respiratory distress syndrome (ARDS)

A novel zinc chelate complex containing both phosphorus and nitrogen for improving the flame retardancy of low density polyethylene

A novel metal chelate complex containing phosphorus, nitrogen and zinc (II) ion was synthesized and used as the flame retardant of low density polyethylene (LDPE). The zinc chelate complex was synthesized by reacting zinc acetate with the ligand of tetraethyl (1,2-phenylenebis(azanediyl)) bis (2- hydroxylphenylmethylene) diphosphonate (TEPAPM). The chemical structure of the target Zn-TEPAPM was confirmed by FTIR, 1H NMR, 13C NMR and 31P NMR spectra. The flame retardancy and thermal behavior of LDPE containing various amount of Zn-TEPAPM were investigated by limiting oxygen index test, thermogravimetric (TG) analysis and cone calorimetry. The results show that Zn-TEPAPM can greatly increase the thermal stability, the char formation and smoke suppression ability of LDPE. The TG curves show that even when the filler content of Zn-TEPAPM is as low as 1 wt% in LDPE, the onset degradation temperature of LDPE is increased from 429 °C to 442 °C, and the maximum degradation temperature is increased from 469 °C to 488 °C. Also, a reduction of 32% for the peak heat release rate (PHRR) is obtained in the cone test. Moreover, Zn-TEPAPM is demonstrated to be a very effective synergist of ammonium polyphosphate (APP). When 1 wt% of Zn-TEPAPM was introduced into the LDPE/APP (mass ratio 80/19) blend, the PHRR value is reduced by 32%, compared with that of LDPE/APP blend without Zn-TEPAPM, and the char layer becomes more compact and intact