Nanofibers from recycle waste expanded polystyrene using natural solvent

Summary A new recycling technique has been developed. In this method, EPS (expanded polystyrene), generally called Styrofoam, is dissolved with natural solvent, d-limonene and electrospun. This method can economically produce the nanofibers. The electrospinning process produces a nonwoven mat of long polymer fibers with diameters in the range of 10–500 nm and high surface areas per unit mass. PS (Polystyrene) polymer dissolved in different solvents such as THF (Tetrahydrofuran), DMF (Dimethylformaide), and DMAc (Dimethylacetamide) etc. may all be electrospun into nanofibers. These solvents cause environmental problem and difficulty of process handling. Natural solvent, d-limonene is used for dissolving PS. PS nanofibers are produced with PS solution using d-Limonene. This paper describes the use of polystyrene (PS) nanofibers electrospun from recycled EPS solution dissolved in d-limonene. The electrospun polystyrene nanofiber diameters vary from 300 to 900 nm, with an average diameter of about 700 nm.     

Solution properties and chain flexibility of poly(p-tert-butylstyrene)

The dilute solution properties of anionically synthesized poly(p-tert-butylstyrene) (PtBS) were studied in tetrahydrofuran, cyclohexane 1,4-dioxane, 1-nitropropane and 2-octanol. Cyclohexane and tetrahydrofuran are good solvents for PtBS, 1,4-dioxane is of intermediate solvent power, and 1-nitropropane and 2-octanol are theta solvents. The unperturbed dimension results show PtBS to be a more extended chain than polystyrene. These observations are interpreted in light of rotational isomeric state (RIS) models for polystyrene and poly(p-chlorostyrene) and experimental data available for polystyrene and its substituted derivatives.     

Enhanced thermal properties of PS nanocomposites formed from inorganic POSS-treated montmorillonite

We have prepared polystyrene/clay nanocomposites using an emulsion polymerization technique. The nanocomposites were exfoliated at up to a 3 wt% content of pristine clay relative to the amount of polystyrene (PS). We used two different surfactants for the montmorillonite: the aminopropylisobutyl polyhedral oligomeric silsesquioxane (POSS) and the ammonium salt of cetylpyridinium chloride (CPC). Both surfactants can intercalate into the layers of the pristine clay dispersed in water prior to polymerization. Although the d spacing of the POSS-intercalated clay is relatively smaller than that of the CPC-intercalated clay, PS more easily intercalates and exfoliates the POSS-treated clay than the CPC-treated clay. IR spectroscopic analysis further confirms the intercalation of POSS within the clay layers. We used X-ray diffraction (XRD) and transmission electron microscopy (TEM) to characterize the structures of the nanocomposites. The nanocomposite prepared from the clay treated with the POSS containing surfactant is exfoliated, while an intercalated clay was obtained from the CPC-treated surfactant. The molecular weights of polystyrene (PS) obtained from the nanocomposite is slightly lower than the virgin PS formed under similar polymerization conditions. The value of T_g of the PS component in the nanocomposite is 8 °C higher than the virgin PS and its thermal decomposition temperature (21 °C) is also higher significantly. The presence of the POSS unit in the MMT enhances the thermal stability of the polystyrene.     

Intercalated clay structures and amorphous behavior of solution cast and melt pressed poly(ethylene oxide)–clay nanocomposites

The polymer nanocomposite (PNC) films consisted of poly(ethylene oxide) (PEO) and sodium cations montmorillonite (MMT) clay were prepared by aqueous solution casting and direct melt press compounding techniques, whereas the films of PEO with trimethyl octadecyl ammonium cations organo‐modified montmorillonite (OMMT) clay were formed by melt pressed technique. The clay concentrations in the nanocomposites used are 1, 2, 3, 5, 10, and 20 wt % of the PEO weight. The X‐ray diffraction patterns of these nanocomposites were measured in the angular range (2θ) of 3.8–30°. The values of basal spacing d₀₀₁ of MMT/OMMT, clay gallery width W_cg, d‐spacings of PEO crystal reflections d₁₂₀ and d₁₁₂, and their corresponding crystallite size L, and the peaks intensity I (counts) were determined for these nanocomposites. Results reveal that the nanocomposites have intercalated clay structures and the amount of intercalation increases with the increase of clay concentration. As compared to melt pressed PEO–MMT nanocomposites, the amount of clay intercalation is higher in aqueous solution cast nanocomposites. At 20 wt % MMT dispersion in PEO matrix, the solution cast PEO–MMT nanocomposite almost changes into amorphous phase. The melt press compounded PEO–OMMT films show more intercalation as compared to the PEO–MMT nanocomposites prepared by same technique. In melt pressed nanocomposites, the PEO crystalline phase significantly reduces when clay concentration exceeds 3 wt %, which is evidenced by the decrease in relative intensity of PEO principal crystalline peaks. The effect of interactions between the functional group (ethylene oxide) of PEO and layered sheets of clay on both the main crystalline peaks of PEO was separately analyzed using their XRD parameters in relation to structural conformations of these nanocomposites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39898.     

Control of fluorescence emission color of benzo 15-crown-5 ether substituted oligo phenylene vinylene-ceramic nanocomposites

Nanocomposites of benzo 15-crown-5 ether substituted oligo phenylene vinylene (CE-OPV) were prepared by solution intercalation into a surface treated bentone clay, B34, in both the presence and absence of Eu³⁺ ions, and were characterized using X-ray diffraction (XRD) and fluorescence techniques. The intercalation of B34 by CE-OPV increases the d-spacing (gallery height) of B34, the increase being more in the presence of metal ion than in its absence. The increase in d-spacing of a related material, poly[1,4,-(2,5-bis (tetra ethylene oxide substituted)) phenylene vinylene (EO-PPV)] due to intercalation into clay is greater than that by CE-OPV. Results on intercalation of small benzo-crown ether molecules themselves into B34 in the presence and absence of Eu³⁺, are also presented to help elucidate the process. The fluorescence emission maxima of the nanocomposites of CE-OPV, CE-OPV-Eu³⁺ and EO-PPV showed a steady blue shift as a function of B34 composition and the results are explained in terms of partial intercalation of the fluorophores into the clay.     

Preparation and crystalline morphology of biodegradable starch/clay nanocomposites

An organically modified clay (o-clay) and a pristine clay (p-clay) were used to prepare biodegradable thermoplastic starch (TPS)/clay nanocomposites by melt processing. The gelatinization behaviour of starch with glycerol/H₂O was investigated and the gelatinized temperature (T_gel) was determined using a polarized optical microscopy (POM) equipped with a hot stage. The morphologies of gelatinized starch and extruded starch were revealed by scanning electron microscopy (SEM). Thermal stabilities of starch/clay nanocomposites were evaluated under N₂ atmosphere using thermogravimetric analysis (TGA). Transparent films of starch/clay hybrids were fabricated by hot pressing. Intercalation of starch into clay galleries and crystalline structure of starch were investigated using X-ray diffraction (XRD). It was found that the increase in d-spacing of organically modified clay was due to starch molecular intercalation while the increase in d-spacing of pristine clay was mostly caused by glycerol intercalation because of the narrow valid d-spacing of pristine clay and special ring-like monomer of starch. The mechanism of starch intercalation in clay galleries was discussed.     

Polystyrene–organoclay nanocomposites prepared by melt intercalation,in situ,and masterbatch methods

In this study, polystyrene (PS)/montmorillonite nanocomposites were prepared by melt intercalation, in situ polymerization, and masterbatch methods. In the masterbatch method, as the first step, a high clay content composite of PS–organoclay (masterbatch) was prepared by in situ polymerization, and then the prepared masterbatch was diluted to desired compositions with commercial PS in a twin‐screw extruder. The structure and mechanical properties of the nanocomposites were examined. X‐ray diffraction (XRD) analysis showed that the d‐spacing of the in situ formed nanocomposites increased from 32.9 Å for the organoclay powder to 36.3 and 36.8 Å respectively in nanocomposites containing 0.73 and 1.6 wt% organoclay, indicating intercalation. However, the d‐spacing of the other prepared materials remained nearly unchanged when compared with pure organoclay powder. Thus, at these low clay contents, in situ formed nanocomposites showed the best improvement in mechanical properties including tensile, impact strength, and Young's modulus. In situ polymerization method did not prove to be efficient at high clay loadings in terms of intercalation and mechanical properties. At high clay loadings, the effects of the three methods in promoting mechanical properties were not significantly different from each other. POLYM. COMPOS., 27:249–255, 2006. © 2006 Society of Plastics Engineers     

Lower critical solution temperature behavior of ethylene propylene copolymers in multicomponent solvents

The lower critical solution temperature (LCST) locus for ethylene-propylene copolymers has been determined as a function of pressure in a variety of single and multicomponent solvents. The lower critical end-point temperature (LCEP), which is the intersection of the LCST locus with the vapor-pressure curve, was found to be predictable from the solvent density as previously established for single-component solvents by Charlet and Delmas.¹ Dissolving a low-molecular hydrocarbon gas such as propylene in an alkane has a dramatic effect on lowering the LCEP, and can reduce phase-separation temperatures to levels at which this technique becomes attractive as a practical method for polymer recovery from diluents such as those used in solution polymerizations. Temperatures considerably above the LCEP are needed to minimize the residual polymer concentration in the solvent in the two-liquid-phase region. The solvent critical temperature must be approached for essentially complete elimination of the polymer from the solvent phase. The LCST locus was found to be a linear function of pressure for all of the systems investigated, and the slope of the line, d(LCST)/dP, could be well correlated as a function of solvent density and critical temperature. From the relationship between the LCEP and solvent density and the correlation for d(LCST)/dP, the location of the LCST locus can be readily predicted from a knowledge of solvent properties.     

Intercalation of cetyl trimethylammonium ion into sericite in the solvent of dimethyl sulfoxide

In order to improve the microenvironment between layers of sericite in the manufacture of polymer/sericite nanocomposites, a pre-modified sericite was intercalated by cetyl trimethylammonium ion (CTA⁺) in a dimetzhyl sulfoxide (DMSO) solvent. The relevant experimental conditions, such as intercalating time, temperature, solid content and pH value, were optimized, and the intercalated sericite was characterized by X-ray diffraction, Fourier transform infrared, and X-ray photoelectron spectroscopy analyses. At an intercalation rate of 94%, the amount of CTA⁺ intercalated in the interlayer space of sericite was 36.3% and an expansion of d₀₀₁ value from 1.00 nm to 5.07 nm was observed. The intercalated CTA⁺ in the interlayer space of sericite adopted a paraffin-type bilayer configuration with a tilting angle of 53.6°. Due to its unique structure, DMSO would be better than water as the solvent for intercalation of organic cations. The intercalated sericite was more suitable to combine with polymer to form polymer/sericite nanocomposites.     

Polystyrene nanocomposite materials by in situ polymerization into montmorillonite–vinyl monomer interlayers

A different series of new polystyrene–clay nanocomposites have been prepared by grafting polymerization of styrene with vinyl‐montmorillonite (MMT) clay. The synthesis was achieved through two steps. The first step is the modification of clay with the vinyl monomers, such as N,N‐dimethyl‐n‐octadecyl‐4‐vinylbenzyl‐ammonium chloride, n‐octadecyl‐4‐vinylbenzyl‐ammonium chloride, triphenyl‐4‐vinylbenzyl‐phosphonium chloride, and tri‐n‐butyl‐4‐vinylbenzyl‐phosphonium chloride. The second step is the polymerization of styrene with different ratios of vinyl‐MMT clay. The materials produced were characterized by different physical and chemical methods: (1) IR spectra, confirming the intercalation of the vinyl‐cation within the clay interlayers; (2) thermogravimetric analysis (TGA), showing higher thermal stability for PS–nanocomposites than polystyrene (PS) and higher thermal stability of nanocomposites with of phosphonium moieties than nanocomposites with ammonium moieties; (3) swelling measurements in different organic solvents, showing that the swelling degree in hydrophobic solvents increases as the clay ratio decreases; (4) X‐ray diffraction (XRD), illustrating that the nanocomposites were exfoliated at up to a 25 wt % of organoclay content; and (5) scanning electron microscopy (SEM), showing a complete dispersion of PS into clay galleries. Also, transmission electron microscopy (TEM) showed nanosize spherical particles of ～ 150–400 nm appearing in the images. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3739–3750, 2007     

X‐ray diffraction studies and phase volume determinations in poly(ethylene glycol)–montmorillonite nanocomposites

Poly(ethylene glycol)–montmorillonite nanocomposites were prepared by both solution and melt intercalation methods with a range of polymer molecular weights and at a range of polymer loadings. Particular attention was given to the reliability of low‐angle X‐ray diffraction results for basal plane spacing and a sound correlation between three diffractometers was obtained (±0.005 nm). Expansion of the basal plane spacing from 1.23 nm to 1.82 nm by solution intercalation was independent of polymer molecular weight in the range 300–20 000. Furthermore, the clay expansion was independent of the method of intercalation; melt intercalation also gave d₀₀₁ = 1.82 nm irrespective of polymer molecular weight. The maximum amount of polymer intercalated by clay and the maximum loading of clay that polymer can sustain were also studied for the determination of nanocomposite formulations. The confined polymer exerts a reduced effective density (670 kg m^?3) in the galleries. Copyright © 2005 Society of Chemical Industry     

Novel role of polymer-solvent and clay-solvent interaction parameters on the thermal, mechanical and optical properties of polymer nanocomposites

Solvent-polymer and solvent-clay interactions are very important in determining the properties of polymer-clay nanocomposites. In the present work, hydrogenated nitrile rubber-sepiolite nanocomposites were prepared and the interaction parameters of various solvents with rubber (χ_AB) and clay (χ_CD) were studied. Nine different sets of solvent combination were chosen based on their solubility parameter. A correlation between thermal, mechanical and optical transmittance properties of polymer-clay nanocomposites and the difference in their interaction parameters with various solvents (χ_AB − χ_CD) was analyzed for the first time. This study helped to identify chloroform/methyl ethyl ketone as the best solvent combination, where temperature at which maximum degradation of the polymer took place was raised by 65 °C and tensile strength and modulus at 100% elongation were enhanced by almost 200% over the neat rubber. The results were correlated with the data of X-Ray Diffraction study, Atomic Force Microscopy and Transmission Electron Microscopy. Finally, thermodynamic interpretation was made to explain the results.     

Synthesis and properties of polystyrene–montmorillonite nanocomposites by suspension polymerization

Organophilic montmorillonite was prepared using ion‐exchange method between sodium ions in clay layers and stearyltrimethyl ammonium chloride in the various solvents, including deionized water, ethanol, acetone, and toluene. The montmorillonite has the largest d₀₀₁ spacing, as determined by X‐ray diffraction in toluene, than the other solvents considered. Ethanol can completely wash out the overexchanged stearyltrimethyl ammonium chloride among layers of montmorillonite. However, deionized water is the preferred ion‐exchange solvent. The thermal stability of organophilic montmorillonite was investigated by high‐resolution thermogravimetric analysis (TGA). Polystyrene–montmorillonite nanocomposites were obtained by suspension free radical polymerization of styrene in the dispersed organophilic montmorillonite. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that montmorillonite had been exfoliated. 5.0 wt % of clay in the synthesized nanocomposite was found to be the optimum content that improved both thermal and mechanical properties over those of pure polystyrene under the experimental conditions applied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 101–109, 2004     

A novel modification on melt intercalation via exothermal MMT

This article presented a novel modification on the melt intercalation. Montmorillonite (MMT) with exothermal enthalpy effect was prepared by the compounding of MMT with AIBN in solution. An exfoliated polystyrene (PS)/MMT nanocomposites could be obtained by the introduction of exothermal MMT via melt mixing, and the comparison with the counterpart indicated the exfoliation of MMT was accelerated by the in situ exothermal enthalpy and nitrogen released during melt intercalation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2230–2236, 2004     

Hexadecyl-functionalized lamellar mesostructured silicates and aluminosilicates designed for polymer-clay nanocomposites. Part II: Dispersion in organic solvents and in polystyrene

Layered mesostructured silicates and aluminosilicates with covalently attached hexadecyl groups (denoted as C₁₆-LMS, C₁₆-LMAS, and a sample with layers whose thickness was increased by additional silicate, C₁₆-SiO₂-LMAS) were investigated as synthetic clays for dispersion and exfoliation in polymer melts. The dispersion of these clays in 13 organic solvents and their performance in polystyrene (PS) nanocomposites were examined. The three synthetic clays dispersed and formed gels in aromatic solvents and in a branched alkyl solvent (2,6,10,14-tetramethylpentadecane, TMPD) based on visual observations and rheology. The elastic moduli (G′) of the toluene/clay dispersions for all three clays were similar when compared at equal inorganic content. The synthetic clays were blended with PS samples of various molecular weights. Melt rheology of the PS/clay nanocomposites showed a dramatic increase in elastic modulus compared with neat PS and formation of a G′ plateau at low frequencies. The plateau occurred at higher G′ values for C₁₆-LMAS than for C₁₆-SiO₂-LMAS or C₁₆-LMS, indicating that C₁₆-LMAS has higher strength and/or higher aspect ratio and can thus withstand the stresses of melt mixing. Increasing the molecular weight of PS increased G′ of the PS/C₁₆-LMAS nanocomposites. By small angle X-ray (SAXS) and transmission electron microscopy C₁₆-LMAS showed better dispersion and a higher aspect ratio in the PS-nanocomposite than C₁₆-SiO₂-LMAS.     

Permanent adsorption of organic solvents in graphite oxide and its effect on the thermal exfoliation

The dispersion of graphite oxide (GO) in organic solvents followed by their evaporation at relative high temperature resulted in a strong adsorption of the solvent molecules in the graphitic interlayers as confirmed by ¹³C magic-angle-spinning NMR. Three series of solvents, alcohols (1-methanol, 1-propanol, 1-pentanol, 1-heptanol), aromatics (benzene, toluene, p-xylene, chlorobenzene) and chloride compounds (dichloromethane, chloroform, carbon tetrachloride) were studied to understand the interaction of graphite oxide with solvents. The distribution of basal interlayer spacing changed due to solvent intercalation and this distribution was particularly different for each solvent series. Even though there was on average 1 solvent molecule per 100 carbon atoms of GO, they had a profound effect on the thermal properties of the resulting GO. The exfoliation temperature was drastically reduced by the presence of the solvents due to the increase of the interlayer spacing and the reducing power of the solvent.     

聚苯乙烯/石墨烯纳米复合材料研究进展

综述了聚苯乙烯/石墨烯纳米复合材料制备方法的研究进展,包括溶液插层法、微球覆盖还原法、原位乳液聚合法、Pickering乳液聚合法、点击化学法、原子转移自由基法,以及聚苯乙烯/石墨烯纳米复合材料在电性能、热性能、流变性能和力学性能等方面的研究进展,并对其应用前景进行了展望。     

Substitution behaviour of an unusual seven-coordinate iron(III) complex in different solvents

In order to clarify the solution chemistry of 3d metal hepta-coordinate complexes, a detailed mechanistic study of the two-step substitution reaction between the “tweezer-like” iron(III) complex, [Fe(dapsox)(H₂O)₂]⁺ (H₂dapsox=2,6-diacetylpyridine-bis-(semioxamazide)), and SCN⁻ was performed in water and methanol as solvents. Based on the observed rate law and reported activation parameters (ΔH^#, ΔS^# and ΔV^#) for both reaction steps in aqueous solution, the operation of an I_a mechanism for the diaqua, an I_d mechanism for the aquathiocyanato, and an I_d or D mechanism for the aquahydroxo forms of the Fe(III) complex, is proposed. The operation of a limiting D mechanism is proposed for both reaction steps in methanol as solvent.     

Montmorillonite-carbon nanocomposites with nanosheet and nanotube structure: Preparation,characterization and structure evolution

In this study, the preparation of montmorillonite (Mt)-polyvinyl alcohol (PVA) nanocomposites (MtPVAN), and the formation of corresponding Mt carbon nanocomposites with nanosheet and nanotube structures were investigated. MtPVAN was prepared by solution intercalation combined with the dispersion method of ultrasonic radiation (UR) and mechanical stirring (MS). XRD analysis showed that the MtPVAN with d₀₀₁ at 2.16 nm were successfully obtained with optimum mass ratio of 1:1.5 (Mt:PVA) and solid content of 10%. Then, the Mt-carbon, nanocomposites (d₀₀₁ = 1.56 nm) with sandwich structure was prepared by carbonizing MtPVAN at 400 °C in nitrogen atmosphere for 3 h; and Mt-carbon nanosheets or nanotubes with carbon content of 5.10% was obtained by exfoliating the sandwich-like Mt-carbon nanocomposites with further airflow pulverization process. The average diameter and the thickness of the Mt-carbon nanosheets was about 2 μm and 10 nm, respectively; while the diameter of the nanotubes was 7–80 nm. The mechanism of the formation and the structure evolution of the Mt-carbon nanocomposites were also discussed.     

Solvent dependence of the viscous and viscoelastic properties of a high molecular weight polystyrene in moderately concentrated solution

The steady-flow viscosity and viscoelastic behaviour of two solutions of a sensibly monodisperse polystyrene of high molecular weight (M_w = 498 000) have been measured over a temperature range of 100°C for identical concentrations of 20.55 wt.%. Toluene and methyl ethyl ketone were chosen as the two low viscosity solvents having, respectively, good and marginal thermodynamic affinities. Dynamic viscoelastic measurements were made at a frequency of 41 kHz using travelling torsional waves. At this frequency, both solutions exhibit behaviour characteristic of the rubbery region, and the ratio of the dynamic viscosity normalised by dividing by the corresponding solvent viscosity is independent of the solvent until the onset of the glass transition region with decreasing temperature. The storage shear modulus of the toluene solution in the rubbery region is higher than for the MEK solution, indicating a higher entanglement density in the better solvent and a larger polymer radius. Some features of the results in the poor solvent (MEK) appear to indicate that, as the temperature decreases, partial exclusion of the solvent leads to the formation both of stronger entanglements and of macromolecular aggregates or bundles, as suggested by Dreval and others^6–8,11,22.