Photopolymerization and toughening performance in polypropylene of hyperbranched polyurethane acrylate

A novel UV-curable hyperbranched polyurethane acrylate (HUA) was synthesized and found to polymerize rapidly in the presence of 5 wt.% benzophenone in N₂ under UV exposure. The photopolymerization kinetics of HUA was studied by differential photocalorimetry (DPC). Its toughening effect for polypropylene (PP) was investigated by tensile and impact tests of the UV irradiated PP/HUA blends. The morphological structures and thermal behavior were determined by polarized optical microscopy, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The obtained results demonstrate that (1) the maximum photopolymerization rate increases with raising temperature up to 140 °C, whereas decreases at above 150 °C. The activation energy of 19 kJ mol⁻¹ for the photopolymerization was obtained at below 140 °C from the Arrhenius plot, while it is negative at above 150 °C. (2) The incorporation of 5 wt.% HUA greatly improved the notched impact strength of PP matrix with a slight improvement in the tensile strength and without obvious decline in breaking elongation. These results correlate well with SEM observation. (3) During the UV irradiation of PP/HUA blends, PP can be crosslinked/grafted with the cured HUA particles, resulting in the increase of the impact strength of PP matrix. (4) The cured HUA particles in the PP/HUA blends act as heterogeneous nucleation agent for PP, which results in the decrease of spherulite size and less perfection of PP crystals.     

Mechanical properties and strain-rate effect of EVA/PMMA in situ polymerization blends

Transparent EVA/PMMA sheets are produced via in situ polymerization of MMA in this work. In the presence of the EVA-graft-PMMA (EVA-g-PMMA), which is synthesized by using tert-butyl peroctoate (t-BO) as initiator during MMA polymerization, EVA can be well dispersed in the PMMA matrix. Both tensile fracture energy and Izod impact strength of the EVA/PMMA blends are higher than those of the neat PMMA. SEM photos show that the grafted copolymer also prevents the dispersed EVA particles from being pulled out from the fracture surface. While the EVA/PMMA blends are investigated at room temperature over the strain rates of four decades (from 1.6 × 10⁻⁴ to 0.16 s⁻¹). It has an obvious transition, whereas the neat PMMA remains brittle over the entire range of strain rates.     

FTIR study on the nature of water sorbed in polypropylene (PP)/ethylene alcohol vinyl (EVOH) films

FTIR transmission spectroscopy, along with gravimetric analysis and scanning electron microscopy (SEM), have been used to investigate the structure of water sorbed in PP/EVOH films. Aims of this investigation were to determine water content spectroscopically, to elucidate the different types of interaction that water molecules form with the macromolecular network and their change as a function of blend composition, morphology and the state (gaseous or liquid) of the water contacting with the PP/EVOH system at equilibrium.The extinction coefficients (ε) of the water sensitive bands (ν_OH, δ_OH, 2150 and 700 cm⁻¹) are proportional to the EVOH content. These results are explained by the phase separation between PP and EVOH and the increasing size of the dispersed EVOH spheres with the EVOH content. Moreover, the ε values suggest that when the films are in contact with water vapor, most of the water sorbed locates around the hydrogen bonding sites of the polymer although the effective hydration region around the EVOH residues should be much larger than the primary hydration region. Besides, “bulk water”, generally categorized as “free water”, is lacking in the polymer blends under our experimental conditions. When they contact with liquid water both the water uptake and the ε values are changed, but these variations are not large enough to assume the formation of “bulk water”. Band decomposition of the O-H stretching vibration (ν_OH) on the basis of the four-state model supports the assumption of the absence of “water-rich domains”, regardless of the blend composition or whether the PP/EVOH film contacts with liquid water or water vapor. Besides, either in contact with water vapor or liquid water, the more hydrophobic mixtures (90/10) show the greatest effect of perturbation with respect to pure water for the “weaker hydrogen bonded” water. Conversely, the interactions between the “strongly bound” water and OH groups in the EVOH chains become stronger with increasing hydrophilicity of the blends and this type of water has a greater plasticising efficiency. Furthermore, these structural changes are greater for liquid water than for water vapor and this trend is equally observed for mixtures of different hydrophilicity.     

Determination of total arsenic and toxicologically relevant arsenic species in fish by using electrothermal and hydride generation atomic absorption spectrometry

A scheme for the determination of total As by electrothermal atomic absorption spectrometry (ETAAS) and the sum of toxicologically relevant arsenic species (As(III), As(V), monomethylarsonate (MMA) and dimethylarsinate (DMA) using hydride generation AAS (HGAAS) in fish samples was developed. Simple and fast microwave assisted extraction in tetramethylammonium hydroxide (TMAH, 0.075% m / v) or in water-methanol mixture (80 + 20 v / v) for 20 min is proposed for quantitative leaching of arsenic species from fish tissue. Total As was measured by ETAAS directly in the TMAH extract under optimal instrumental parameters (pyrolysis temperature 1400 °C and atomization temperature 2000 °C) with Pd as modifier ensuring thermal stabilization and isoformation of all extracted arsenic species. The analytical features of the method are as follows: limit of detection (LOD) 0.45 μg g^− 1 (dry wt.), within-run and between-run precision in the range 4-8% and 5-12%, respectively, for arsenic contents 0.5-30 μg g^− 1 and recoveries 98-102%. The sum of toxicologically relevant arsenic species (As(III) + As(V) + MMA + DMA) was determined by flow injection HGAAS directly from the TMAH extract or water-methanol mixture and trapping of arsines onto Zr-Ir coated graphite tube followed by ETAAS measurement. l-cysteine is used as reagent for leveling off responses of different arsenic species in the presence of TMAH or water-methanol mixture. The LODs achieved are 0.0038 and 0.0031 μg g^− 1 (dry wt.), respectively, for fish extracts in TMAH and in water-methanol mixture. Within-batch and between-batch RSDs are in the range 3-5% and 4-7% for arsenic contents of 0.009-0.25 μg g^− 1 (dry wt.) for TMAH extracts and 2-4% and 3-6% for methanol water extracts, respectively. Selective reaction media for generation of respective hydrides from arsenic species were recommended for further speciation purposes in methanol-water extracts, viz. citrate buffer (pH 5.2) for the determination of As(III), 0.2 mol L^− 1 acetic acid for the determination of As(III) + DMA and 7 mol L^− 1 hydrochloric acid for the determination of inorganic As(III) + As(V). LODs are 0.0035, 0.0051 and 0.0046 μg g^− 1 (dry wt.) for As(III), DMA and As(V). The relative standard deviation is 4-8% for three arsenic species at As levels of 0.009-0.5 μg g^− 1 (dry wt.). The accuracy of the proposed speciation scheme is confirmed by the analysis of certified reference materials.     

Structural interaction and gas barrier properties of ethylene‐vinyl alcohol/tin phosphate glass composites

The strength of interaction between tin phosphate glass (PGlass) filler droplets and an ethylene‐vinyl alcohol (EVOH) matrix were investigated by image, thermal, and rheological analysis. 10% PGlass droplets in EVOH were smaller than those previously observed in maleated polypropylene. Analysis using the Fox equation showed that EVOH/97 °C T_g PGlass composites are not miscible systems. Dynamic shear and extensional rheology data of those composites exhibited a weak physical network, with relaxation times longer than that of pure EVOH at all strain rates. The tensile properties of the EVOH/10 vol % PGlass composite showed it to be more ductile and flexible than a typical polymer/inorganic filler system, supporting interaction between PGlass and EVOH sufficient to interrupt polymer–polymer hydrogen bonding. While undrawn EVOH/PGlass composite films showed increased oxygen gas permeability when compared to undrawn neat EVOH film, the drawn composite films exhibited oxygen permeability 6–7 times lower than that of neat EVOH, attributed to the presence of high aspect ratio PGlass particles after orientation. The concept of hydrogen bonding between polymer and PGlass can likely be applied to other polymers such as polyamides which possess numerous hydrogen bonding sites. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 989–998     

Influence of SEBS-g-MA on morphology, mechanical, and thermal properties of PA6/PP/organoclay nanocomposites

Polyamide 6/polypropylene (PA6/PP = 70/30 parts) blends containing 4 phr (parts per hundred resin) of organically modified clay (organoclay) toughened with maleated styrene-ethylene-butylene-styrene (SEBS-g-MA) were prepared by melt compounding using co-rotating twin-screw extruder followed by injection molding. X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to characterize the structure of the nanocomposites. The mechanical properties of the nanocomposites were determined by tensile, flexural, and notched Izod impact tests. The single edge notch three point bending test was used to evaluate the fracture toughness of SEBS-g-MA toughened PA6/PP nanocomposites. Thermal properties were studied by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). XRD and TEM results indicated the formation of the exfoliated structure for the PA6/PP/organoclay nanocomposites with and without SEBS-g-MA. With the exception of stiffness and strength, the addition of SEBS-g-MA into the PA6/PP/organoclay nanocomposites increased ductility, impact strength and fracture toughness. The elongation at break and fracture toughness of PA6/PP blends and nanocomposites were increased with increasing the testing speed, whereas tensile strength was decreased. The increase in ductility and fracture toughness at high testing speed could be attributed to the thermal blunting mechanism in front of crack tip. DSC results revealed that the presence of SEBS-g-MA had negligible effect on the melting and crystallization behavior of the PA6/PP/organoclay nanocomposites. TGA results showed that the incorporation of SEBS-g-MA increased the thermal stability of the nanocomposite.     

Analysis of thermomechanical reprocessing effects on polypropylene/ethylene octene copolymer blends

The impact of recycling by grinding and re-extrusion on the physical and mechanical properties of polypropylene (PP)/ethylene octene copolymer (EOC) blends was investigated. The considered EOC content was 0 wt. %, 10 wt. % and 20 wt. %, and the investigated number of recycling passes (extrusions) was 0, 1, 3 and 6. Up to 6 re-extrusions, an increase of the melt flow index (MFI), a slight increase of the crystallinity, a slight decrease of the decomposition temperature (T_onset), and no significant oxidation were noted. Therefore, the recycling of the blends induces thermomechanical degradation by chain scission without oxidation. Increasing the content of EOC increases the MFI and the T_onset of the PP blends. The first recycling procedure induced an increase of the Young's modulus and tensile yield stress, while for higher recycling numbers, these two parameters dropped. The EOC inclusions stabilized the tensile elongation at break up to 3 recycling procedures due to a decrease of their size and a homogenization of their shape, while that of neat PP continuously decreased with recycling numbers.     

Molecular dynamics simulation on ion-pair association of NaCl from ambient to supercritical water

Molecular dynamics (MD) simulations for aqueous NaCl solution were performed from ambient to supercritical conditions (25 °C, 1.0 g cm⁻³; 250–350 °C, 0.67–0.8 g cm⁻³; 380 °C, 0.2–0.8 g cm⁻³; and 400–600 °C, 0.4 and 0.7 g cm⁻³) in the canonical ensemble to examine how the hydration structure relates with the thermodynamics of the ion-pair association. Hydration structure and the potential of mean force (PMF) of Na⁺Cl⁻ ion-pair were calculated. Ion-pair association constants were also calculated from the PMFs. Energies and entropies of the ion-pair at arbitrary inter-ionic distances from 2.0 to 8.0 Å were evaluated from the temperature derivative of the PMFs. From the calculation of energies and entropies, Na⁺–Cl⁻ pair association was found to be endothermic and promoted by the entropy gain. PMFs had minimums and a slight maximum corresponding to CIP, SShIP, and the transition state between CIP and SShIP, and similar minimums and maximum were only observed for the energy term and not clearly observed for the entropy term. This result indicates that the shape of the PMF and stability of SShIP are determined by the energy of the system. Relationship between the hydration structure and the energy of the system was examined and it was confirmed that the hydration structure in the first hydration shell of the ion-pair was one of the important factor, which made the minimums and maximum in the energy terms and PMFs, and stabilized the SShIP structure.     

Preparation and characterization of poly(o-methoxyaniline)/Na-MMT clay nanocomposite via emulsion polymerization: Electrochemical studies of corrosion protection

A series of poly(o-methoxyaniline) (PMA)/Na⁺-montmorillonite (MMT) clay nanocomposite (Na⁺-PCN) materials have been successfully prepared by in situ emulsion polymerization in the presence of inorganic nanolayers of hydrophilic Na⁺-MMT clay with DBSA and APS as surfactant and initiator, respectively. The as-synthesized Na⁺-PCN materials were characterized by Fourier-transformation infrared (FTIR) spectroscopy, wide-angle powder X-ray diffraction (XRD) and transmission electron microscopy (TEM).Na⁺-PCN materials in the form of coatings with low loading of Na⁺-MMT clay (e.g., 5 wt.%, CLMA5) on cold rolled steel (CRS) were found much superior in corrosion protection over those of neat PMA based on a series of electrochemical measurements of corrosion potential, polarization resistance, corrosion current and impedance spectroscopy in 5 wt.% aqueous NaCl electrolyte. The molecular weight of PMA extracted from Na⁺-PCN materials and net PMA were determined by gel permeation chromatography (GPC) with NMP as eluant. Effects of material composition on the optical properties, electrical conductivity, thermal stability and surface morphology of neat PMA and/or a series of Na⁺-PCN materials, in the form of solution, powder-pressed pellet and fine powder, were also studied by ultraviolet-visible spectra, four-point probe technique, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), respectively.     

Effect of nucleating agent on the brittle–ductile transition behavior of polypropylene/ethylene–octene copolymer blends

In the present work, α‐form nucleating agent 1,3:2,4‐bis (3,4‐dimethylbenzylidene) sorbitol (DMDBS, Millad 3988) is introduced into the blends of polypropylene/ethylene–octene copolymer (PP/POE) blends to study the effect of the nucleating agent on the toughness of PP/POE blends through affecting the crystallization behavior of PP matrix. Compared with the PP/POE blends, in which the toughness of the blends increases gradually with the increasing content of POE and only a weak transition in toughness is observed, addition of 0.2 wt % DMDBS induces not only the definitely brittle‐ductile transition at low POE content but also the enhancement of toughness and tensile strength of the blends simultaneously. Study on the morphologies of impact‐fractured surfaces suggests that the addition of a few amounts of DMDBS increases the degree of plastic deformation of sample during the fracture process. WAXD results suggest that POE induces the formation of the β‐form crystalline of PP; however, DMDBS prevents the formation of it. SEM results show that the addition of DMDBS does not affect the dispersion and phase morphologies of POE particles in PP matrix. DSC and POM results show that, although POE acts as a nucleating agent for PP crystallization and which enhances the crystallization temperature of PP and decreases the spherulites size of PP slightly, DMDBS induces the enhancement of the crystallization temperature of PP and the decrease of spherulites size of PP more greatly. It is concluded that the definitely brittle–ductile transition behavior during the impact process and the great improvement of toughness of the blends are attributed to the sharp decrease of PP spherulites size and their homogeneous distribution obtained by the addition of nucleating agent. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 577–588, 2008     

Thermal oxidative stability and effect of water on gas transport and mechanical properties in PA6‐EVOH films

The thermal oxidative stability and the effect of water on gas transport and mechanical properties of blends of polyamide 6 (PA6) with ethylene‐co‐vinyl alcohol (EVOH) and EVOH modified with carboxyl groups (EVOH‐COOH) have been investigated. The presence of EVOH reduces water vapor and oxygen gas permeability of polyamide, as well as small amounts of EVOH‐COOH further improve barrier properties, especially to oxygen. This has been explained in terms of improved interactions of the blend constituents in the amorphous phase, due to ionic linkages between the polyamide amino groups and the carboxyls of modified EVOH. The permeation to gases was found to increase with the amount of sorbed water. The morphology of the samples was found to have an effect on barrier properties, as the presence of EVOH causes the PA6 α crystalline form to increase, lowering the permeability to oxygen and water vapor. Mechanical properties are strongly affected by water sorption, as tensile modulus and strength decrease with increasing water content. Chemiluminescence (CL), infrared spectroscopy (FTIR), and tensile test were employed in order to assess the correlation between chemical composition and the thermal oxidative stability of the films aged at 110 °C in air. CL experiments suggest that the presence of EVOH and EVOH‐COOH efficiently inhibits the formation of peroxidized species during the processing, and increases the thermal oxidative stability of the films. Infrared spectroscopy showed a build‐up of carbonyl absorption in the range 1700–1780 cm^?1, due to the formation of oxidation products, which is greater in the case of the pure polymer. Tensile tests on films revealed a reduction in ductility as a result of ageing for neat PA6, whereas in comparison the blends exhibit a far better long‐term stability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 840–849, 2007     

Poly(ethylene-co-vinyl alcohol) and poly(methyl methacrylate) blends: Phase behavior and morphology

In this work blends of poly(ethylene-co-vinyl alcohol) (EVOH) with different ethylene contents (27, 32, 38 and 44 mol%) and poly(methyl methacrylate) (PMMA) were prepared by mechanical mixing in the melted state. The miscibility and melting behavior as a function of blend composition and the ethylene content in EVOH copolymers were investigated by means of differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The morphology of the cryofractured surfaces was examined by scanning electron microscopy (SEM). DSC and DMTA data show that EVOH/PMMA blends are immiscible, independent of EVOH and blend composition. The SEM analysis in agreement with DMTA analysis indicates that the morphology of phases depends on the blend composition, with phase inversion occurring as the concentration of one or other polymer component increases. However, the copolymer composition apparently does not affect the domain size distribution for blends containing 20 wt% of EVOH or 20 wt% of PMMA. A better phase adhesion is observed mainly for blends with 50 wt% of each polymer component.     

Melt blending of ethylene‐vinyl alcohol copolymer/clay nanocomposites: Effect of the clay type and processing conditions

Ethylene‐vinyl alcohol copolymer (EVOH)/clay nanocomposites were prepared via dynamic melt blending. The effect of the processing parameters on blends containing two clay types in different amounts was examined. The blends were characterized with a Brabender plastograph and capillary rheometer, differential scanning calorimetry, dynamic mechanical thermal analysis (DMTA), X‐ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). XRD showed advanced EVOH intercalation within the galleries, whereas TEM images indicated exfoliation, thereby complementing the XRD data. A dilution process with EVOH and clay treatment in an ultrasonic bath before melt blending did not add to the intercalation level. Different trends were observed for the EVOHs containing two different clay treatments, one claimed to be treated for EVOH and the other for amine‐cured epoxy. They reflected the differences in the amounts of the strongly interacting polymer for the two nanocomposites. Thermal analysis showed that the melting temperature, crystallization temperature, and heat of fusion of the EVOH matrix sharply decreased with both increasing clay content and processing times. Significantly higher viscosity levels were obtained for the blends in comparison with those of the neat polymer. The DMTA spectra showed higher glass‐transition temperatures for the nanocomposites in comparison with those of the neat EVOH. However, at high clay loadings, the glass‐transition temperature remained constant, presumably because of an adverse plasticizing effect of the low moleculared mass onium ions treating the clays. The storage modulus improved when clay treated for EVOH was used, and it deteriorated when amine‐cured epoxy clay was incorporated, except for the sonicated clay. TGA results showed significant improvements in the blends' thermal stability in comparison with that of the neat EVOH, which, according to TEM, was greater for the intercalated structures rather than for exfoliated ones. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1741–1753, 2002     

Comparison of adsorption equilibrium of fructose, glucose and sucrose on potassium gel-type and macroporous sodium ion-exchange resins

Adsorption equilibrium of fructose, glucose and sucrose was evaluated on sulfonated poly(styrene-co-divinylbenzene) cation-exchange resins. Two types of resins were used: potassium (K⁺) gel-type and sodium (Na⁺) macroporous resins. Influence of the cation and effect of the resin structure on adsorption were studied. The adsorption isotherms were determined by the static method in batch mode for mono-component and multi-component sugar mixtures, at 25 and 40 °C, in a range of concentrations between 5 and 250 g L⁻¹. All adsorption isotherms were fitted by a linear model in this range of concentrations. Sugars were adsorbed in both resins by the following order: fructose > glucose > sucrose. Sucrose was more adsorbed in the Na⁺ macroporous resin, glucose was identically adsorbed, and fructose was more adsorbed in the K⁺ gel-type resin. Data obtained from the adsorption of multi-component mixtures as compared to the mono-component ones showed a competitive effect on the adsorption at 25 °C, and a synergetic effect at 40 °C. The temperature increase conducted to a decrease on the adsorption capacity for mono-component sugar mixtures, and to an increase for the multi-component mixtures. Based on the selectivity results, K⁺ gel-type resin seems to be the best choice for the separation of fructose, glucose and sucrose, at 25 °C.     

Thermodynamic representation of the NaCl + Na2SO4 + H2O system with electrolyte NRTL model

A comprehensive thermodynamic model based on the electrolyte NRTL (eNRTL) activity coefficient equation is developed for the NaCl + H₂O binary, the Na₂SO₄ + H₂O binary and the NaCl + Na₂SO₄ + H₂O ternary. The NRTL binary parameters for pairs H₂O-(Na⁺, Cl⁻) and H₂O-(Na⁺, SO₄²⁻), and the aqueous phase infinite dilution heat capacity parameters for ions Cl⁻ and SO₄²⁻ are regressed from fitting experimental data on mean ionic activity coefficient, heat capacity, liquid enthalpy and dissolution enthalpy for the NaCl + H₂O binary and the Na₂SO₄ + H₂O binary with electrolyte concentrations up to saturation and temperature up to 473.15 K. The Gibbs energy of formation, enthalpy of formation and heat capacity parameters for solids NaCl_(s), NaCl·2H₂O_(s), Na₂SO_4(s) and Na₂SO₄·10H₂O_(s) are obtained by fitting experimental data on solubilities of NaCl and Na₂SO₄ in water. The NRTL binary parameters for the (Na⁺, Cl⁻)-(Na⁺, SO₄²⁻) pair are regressed from fitting experimental data on dissolution enthalpies and solubilities for the NaCl + Na₂SO₄ + H₂O ternary.     

The stability of polyaniline in strongly alkaline or acidic aqueous media

Polyaniline (PANI) base has been suspended in 9 M potassium hydroxide at 20 °C or 90 °C for various time intervals extending to 4 months. The fraction of acetone-soluble material increased from 1.2 wt.% to 4.5 wt.% after exposure to an alkaline medium for 60 days at 20 °C. Gel-permeation chromatography indicates that the aggregation of PANI is reduced, while the chain degradation itself is negligible. FTIR spectroscopy confirms this trend and the absence of hydrolytic changes in the PANI structure. Polyaniline retains the ability to be reprotonated with a 1 M sulfuric acid to a conducting form. No marked changes in the molecular structure have been found, even after suspension of PANI in 9 M KOH at 90 °C for 60 days.Similar immersion of PANI salt in 5 M sulfuric acid at 20 °C was responsible for changes in the protonation, and the mass increased by 11 wt.%. This was explained by the exchange of the original sulfate or chloride counter-ions for hydrogen sulfate anions or by the protonation of secondary amine sites in PANI in addition to imine ones. The changes in the molecular structure are discussed on the basis of FTIR spectra. The conductivity decreased from 1.2 S cm⁻¹ to ∼10⁻³ S cm⁻¹ but no time-dependence of conductivity was observed. There was no fraction of PANI soluble in acetone. PANI in the protonated state is thus stable also in the strongly acidic medium.The study is supplemented by the assessment of the thermal stability of PANI base, which is of importance for the processing of PANI. Loss of moisture has been observed after exposure to 250 °C for 10 h in both nitrogen atmosphere and in air. Good stability was found at 350 °C only in the nitrogen atmosphere, while a marked mass loss in weight was registered in air.     

Synergistic effect of nanoflaky manganese phosphate on thermal degradation and flame retardant properties of intumescent flame retardant polypropylene system

Nanoflaky manganese phosphate (NMP) was synthesized from manganese nitrate and trisodium phosphate dodecahydrate, and used as a synergistic agent on the flame retardancy of polypropylene (PP)/intumescent flame retardant (IFR) system. The thermogravimetric analysis (TGA), real time Fourier-transform infrared (RTFTIR) spectroscopy measurements, cone calorimeter (CONE) and microscale combustion calorimeter (MCC) were used to evaluate the synergistic effects of NMP on PP/IFR system. When IFR + NMP was fixed at 20 wt% in flame retardant PP system, the TGA tests showed that NMP could enhance the thermal stability of PP/IFR system at initial temperature from about room temperature to 440 °C and effectively increase the char residue formation. The RTFTIR results revealed that NMP could clearly change the decomposition behavior of PP in PP/IFR system, which promotes decomposition at the initial temperature from about room temperature to 260 °C and forms more effective barrier layer to protect PP from decomposing at high temperature from about 260 °C to 500 °C. The CONE tests indicated that the addition of NMP in PP/IFR system not only reduced the peak heat release rate (HRR), but also prolonged the ignition time. The MCC results revealed that PP/IFR/NMP system generated less combustion heat over the course of heating than that of PP/IFR system. And scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to explore the char residues of the PP/IFR systems with and without NMP.     

Aluminum phosphate dispersed on a cellulose acetate fiber surface: Preparation, characterization and application for Li, Na and K separation

Cellulose acetate fibers with supported highly dispersed aluminum phosphate were prepared by reacting aluminum-containing cellulose acetate (Al₂O₃=3.5 wt.%; 1.1 mmol g⁻¹ aluminum atom per gram of the material) with phosphoric acid. Solid-state NMR spectra (CPMAS ³¹P NMR) data indicated that HPO₄²⁻ is the species present on the fiber surface. The specific concentration of acidic centers, determined by ammonia gas adsorption, is 0.50 mmol g⁻¹. The ion exchange capacities for Li⁺, Na⁺ and K⁺ ions were determined from ion exchange isotherms at 298 K and showed the following values (in mmol g⁻¹): Li⁺=0.03, Na⁺=0.44 and K⁺=0.50. The H⁺/Li⁺ exchange corresponds to the model of the ideal ion exchange with a small value of the corresponding equilibrium constant K=1.1×10⁻². Due to the strong cooperative effect, the H⁺/Na⁺ and H⁺/K⁺ ion exchange is non-ideal. These ion exchange equilibria were treated with the use of models of fixed bi- or tridentate centers, which consider the surface of the sorbent as an assemblage of polyfunctional sorption centers. Both the observed ion exchange capacities with respect to the alkaline metal ions and the equilibrium constants were discussed by taking into consideration the sequence of the ionic hydration radii for Li⁺, Na⁺ and K⁺. The matrix affinity order for the ions decreases as the hydration radii of the cations increase, i.e. Li⁺>Na⁺>K⁺. The high values of the separation factors S_Na⁺/Li⁺ and S_K⁺/Li⁺ (up to several hundred) provide quantitative separation of Na⁺ and K⁺ from Li⁺ from a mixture containing these three ions.     

Effect of temperature on the performance of proton batteries based on chitosan–NH4NO3–EC membrane

Membranes of chitosan-based proton conductor polymer electrolyte were prepared by dissolving chitosan powder, ammonium nitrate (NH₄NO₃) salt and ethylene carbonate (EC) plasticizer in acetic acid solution. The temperature dependence of the chitosan-based membrane system was found to obey the Arrhenius relationship. The sample with the highest conductance, 18 wt.% CA + 12 wt.% NH₄NO₃ + 70 wt.% EC (CA40N70E), also possesses the lowest activation energy. From linear sweep voltammetry (LSV) results, the membrane is electrochemically stable at a potential of 1.6–1.8 V and a temperature of 298–353 K. The cells were fabricated using zinc powder (Zn) + zinc sulfate heptahydrate (ZnSO₄·7H₂O) + acetylene black (AB) + polytetrafluoroethylene (PTFE)|CA40N70E|manganese (IV) oxide (MnO₂) + AB + PTFE. The open circuit voltages of the cells are decreases as temperature increases, the same trend as that obtained by LSV. The cell performance is excellent at 333 K, with discharge capacity of 42.7 mAh, internal resistance of 16.8 Ω, maximum power density of 14.6 mW cm⁻² and a short-circuit current density of 31.0 mA cm⁻². However, at temperatures above 333 K, decomposition of the membrane degraded the electrochemical properties of the cells.     

Kinetics of styrene emulsion polymerization in the presence of montmorillonite

The effect of the pristine sodium montmorillonite (Na⁺-MMT) on the styrene emulsion polymerizations with different concentrations of SDS ([SDS]) was investigated. At constant [SDS], the polymerization rate is faster for the run with 1 wt.% Na⁺-MMT compared to the counterpart without Na⁺-MMT. Micelle nucleation predominates in the polymerizations with [SDS] ≧ 13 mM. On the other hand, the contribution of the polymerization associated with the Na⁺-MMT platelets increases significantly when [SDS] decreases from 13 to 9 mM. At [SDS] (e.g., 2 mM) < CMC, homogeneous nucleation controls the particle formation process and polymerization kinetics. Moreover, the contribution of the Na⁺-MMT platelets that act as extra reaction loci to the polymerization kinetics is even comparable to the run in the absence of Na⁺-MMT. The resultant polymer particle size, polymer molecular weight and zeta potential were characterized and a preliminary model was developed to qualitatively study the differences between the polymerizations in the presence and absence of 1 wt.% Na⁺-MMT.