Search

In present study, styrene-b-(ethylene-co-butylenes)-b-styrene triblock copolymer (SEBS) and polypropylene (PP) are prepared. This mixing is followed by adding 3, 5 and 10 wt% of nano CaCO3. The morphology and thermal behavior of PP/SEBS/nano-CaCO3 compounds are characterized by different methods. Scanning electron microscopy micrographs of cryo-fractured PP/SEBS/nano-CaCO3 nanocomposites show that with increasing nano-CaCO3 loading, the aggregation becomes worse. However, followed by adding 5 wt% nano-CaCO3 into PP/SEBS nanocomposites, nano-CaCO3 is homogeneously dispersed in PP matrix. The photomicrograph of transmission electron microscopy confirms that SEBS/PP/nano-CaCO3 nanocomposites are formed, as low aggregations of calcium carbonate were well-dispersed in polymer matrix. With a rise in nano-filler content, the tensile and impact strength of PP/SEBS/CaCO3 nanocomposite are fixed while the elastic modulus of PP/SEBS nanocomposites increases followed by adding nano-CaCO3 to polymer blend, which could be due to the acceptable nano-CaCO3 dispersion quality. [ABSTRACT FROM AUTHOR]

In present study, styrene-b-(ethylene-co-butylenes)-b-styrene triblock copolymer (SEBS) and polypropylene (PP) are prepared. This mixing is followed by adding 3, 5 and 10 wt% of nano CaCO3. The morphology and thermal behavior of PP/SEBS/nano-CaCO3 compounds are characterized by different methods. Scanning electron microscopy micrographs of cryo-fractured PP/SEBS/nano-CaCO3 nanocomposites show that with increasing nano-CaCO3 loading, the aggregation becomes worse. However, followed by adding 5 wt% nano-CaCO3 into PP/SEBS nanocomposites, nano-CaCO3 is homogeneously dispersed in PP matrix. The photomicrograph of transmission electron microscopy confirms that SEBS/PP/nano-CaCO3 nanocomposites are formed, as low aggregations of calcium carbonate were well-dispersed in polymer matrix. With a rise in nano-filler content, the tensile and impact strength of PP/SEBS/CaCO3 nanocomposite are fixed while the elastic modulus of PP/SEBS nanocomposites increases followed by adding nano-CaCO3 to polymer blend, which could be due to the acceptable nano-CaCO3 dispersion quality. [ABSTRACT FROM AUTHOR]

Conductive polymer nanocomposites based on carbon nanotubes (CNTs) have wide range of applications in the electronics and energy sectors. For many of these applications, such as the electromagnetic interference (EMI) shielding, high nanofiller loading is typically needed to achieve the desired properties. The high nanofiller concentration deteriorates the composite's tensile strength due to the increase in nanofiller aggregation. In this work, highly conductive CNT/polypropylene (PP) nanocomposite with improved tensile strength was prepared by melt mixing. The effects of CNT content on the processing behavior, microstructure, mechanical and electrical properties of the nanocomposite were investigated. Scanning electron microscopy was used to investigate the composite microstructure. Good level of CNT dispersion with remarkable adhesion at the CNT/PP interface was observed. Based on a theoretical model, the interfacial strength was estimated to be in the range of 36-58 MPa. As a result of thismicrostructure, significant enhancement in ultimate tensile strength was reported with the increase of CNT content. The tensile strength of the 20wt.% CNT/PP nanocompositewas 80% higher than that of the unfilled PP.Moreover, and due to the good dispersion of CNT particles, an electrical percolation threshold concentration of 0.93 wt.% (0.5 vol.%) was obtained. [ABSTRACT FROM AUTHOR]

The pre-eruptive water content of magma is often estimated using crystal-hosted melt inclusions. However, olivine-hosted melt inclusions are prone to post-entrapment modification by H + diffusion as they re-equilibrate with their external environment. This effect is well established for the case of H + loss from olivine-hosted inclusions that have cooled slowly in degassed magma. Here we present evidence for the opposite effect: the addition of H + into inclusions that are held in melts that are enriched in H 2 O with respect to the trapped melts. The compositional variability in a suite of 211 olivine-hosted inclusions from the Laki and Skuggafjöll eruptions in Iceland's Eastern Volcanic Zone indicates that diffusive H + gain governs the H 2 O content of incompatible trace element depleted inclusions. Individual eruptive units contain olivine-hosted inclusions with widely varying incompatible element concentrations but near-constant H 2 O. Furthermore, over 40% of the inclusions have H 2 O / Ce > 380 , significantly higher than the H 2 O/Ce expected in primary Icelandic melts or mid-ocean ridge basalts (150–280). The fact that the highest H 2 O/Ce ratios are found in the most incompatible element depleted inclusions indicates that hydration is a consequence of the concurrent mixing and crystallisation of compositionally diverse primary melts. Hydration occurs when olivines containing depleted inclusions with low H 2 O contents are juxtaposed against more hydrous melts during mixing. Melt inclusions from a single eruption may preserve evidence of both diffusive H + loss and H + gain. Trace element data are therefore vital for determining H 2 O contents of melt inclusions at the time of inclusion trapping and, ultimately, the H 2 O content of the mantle source regions. [ABSTRACT FROM AUTHOR]

The solidification of microstructure of hypereutectic Al-20%Si alloy obtained by mixing high-temperature Al-30%Si alloy melt and low-temperature Al-10%Si alloy melt in a mixing ratio of 1 : 1 was investigated by optical microscopy. A certain amount of AlTi5BRE10 inter alloy was added into high-temperature Al-30%Si alloy melt before mixing. The results showed that the primary Si crystals were refined and passivated by the melt mixing process and a certain amount of AlTi5BRE10 inter alloy further refined the primary silicon and α-Al phase. The coarse plates, petals and irregular triangular-shaped primary Si crystals turned into fine block shapes, and the α-Al phases were spherical. After the melt mixing treatment, the microstructure of the hypereutectic Al-20%Si alloy was composed of a primary α-Al phase, eutectic (α + Si) phase, and the primary silicon, which caused the hypereutectic Al-20%Si alloy to exhibit typical hypoeutectic and hypereutectic characteristics. [ABSTRACT FROM AUTHOR]

Nanocomposites of high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene (PP), polystyrene (PS) and polycarbonate (PC) with thermally reduced graphene were generated by melt mixing. The HDPE nanocomposites had increment in the tensile (>50%) and storage modulus as a function of filler fraction. LLDPE had the highest enhancements of ≈100% in tensile modulus, 60% in break stress and 30% in tensile stress. PS exhibited least extent of property improvement, though the absolute modulus and strength were the highest for PS nanocomposites indicating the final properties of nanocomposites result from a combination of factors like polarity match between polymer and filler, processing conditions and physical properties of the polymer matrix. [ABSTRACT FROM AUTHOR]

• PLA/SiO2:Sr2+: Tb3+ composites were successfully synthesized by melt mixing and characterized. • TEM and XRD were used to determine the physical properties. • The thermal properties of the composites were determined using DSC and TGA. • Photoluminescent behavior of the composites was studied with laser PL. • All the samples emit in the blue vertex as shown by the CIE results. SiO 2 :0.4% Sr2+, x% Tb3+ (0 ≤ x ≤ 0.5) nanophosphor powders were prepared by sol-gel method. The powder samples were dispersed into the PLA polymer matrix through melt mixing method and compression molding to prepare the nanophosphor polymer composite. X-ray diffraction (XRD) patterns showed broad peaks with the position of the peaks shifting and more separating with an increase in Tb3+ concentration. The transmission electron microscope (TEM) images showed darker patches with the introduction of the nanophosphor, which indicates the incorporation of phosphor particles into PLA polymer. Differential scanning calorimeter (DSC) results revealed that the composites show an increase in the cold crystallization temperature (T cc) and slight decrease in the glass transition temperature (T g) as compared to the PLA. Thermogravimetric analysis (TGA) results showed that the thermal stability of the composites show an initial decrease with the incorporation of the fillers, but they become more thermally stable with higher Tb concentration in the fillers. Ultraviolet visible spectroscopy (UV–vis) results showed the decrease in transmittance for the composite compared to the PLA polymer. The photoluminescence (PL) results showed that the incorporation of the Sr2+doped SiO 2 only affected the luminescence intensity, while co-doping with the incorporation of the Sr2+ and Tb3+ ions induced the emissions peaks at 487, 543, 582 and 621 nm, which could be attributed to the 5D 4 → 7F 3 , 7F 4 , 7F 5 , and 7F 6 transitions of Tb3+, respectively. The main aim of this study was to fabricate the light emitting polymer-based material. [Display omitted] [ABSTRACT FROM AUTHOR]

The effect of adding carbon black on the electrical and rheological properties of graphite nanoplatelets/poly(ethylene- butyl acrylate) copolymer composites produced via melt or solution mixing was studied. By adding a small amount of low- or high-structured carbon black to the nanocomposite, the electrical percolation threshold decreased and the final conductivity (at higher filler contents) increased. The effect on the percolation threshold was significantly stronger in case of the high-structured carbon black where replacing 10 wt% of the total filler content with carbon black instead of graphite nanoplatelets reduced the electrical percolation threshold from 6.9 to 4.6 vol%. Finally, the solution mixing process was found to be more efficient leading to a lower percolation threshold. For the composites containing high-structured carbon black, graphite nanoplatelets and their hybrids there was a quite reasonable correlation between the electrical and rheological percolation thresholds. [ABSTRACT FROM AUTHOR]

The electrical percolation threshold of different polyethylene/carbon nanotube nanocomposites was studied as a function of chain structure, matrix viscosity, and the effect of compatibilizer. The lower the viscosity of the matrix the lower is the percolation threshold, regardless of the chain architecture and degree of crystallization. To improve dispersion a series of acrylic acid copolymer are introduced into the system. The highest concentration of acid co-monomer that maintain miscibility with the polyethylene matrix is 5 wt.%. The compatibilizer in its pristine form does not have a significant effect on dispersion and on volume resistivity. When the acidic copolymer was modified with aminomethylpyridine, in order to facilitate π-π interaction with the nanotubes, a 4-decade reduction was recorder for the high viscosity matrices at 10 wt.% compatibilizer loading. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Major elements, trace elements and volatiles were measured in 110 olivine-hosted melt inclusions from the subglacial Skuggafjöll eruption in the Eastern Volcanic Zone of Iceland. Variations in melt inclusion trace element concentrations can be accounted for by incomplete mixing of diverse mantle parental melts accompanied by variable extents of fractional crystallisation. Binary mixing between an incompatible trace element-enriched and depleted melts provides a good fit to observed variations in trace element ratios such as Ce/Y. Surprisingly, the CO2 contents of melt inclusions correlate negatively with their degree of trace element enrichment. Depleted, low-Ce/Y inclusions with ∼1200 ppm CO2 have high CO2/Nb contents (∼400), suggesting that melts experienced little or no CO2 exsolution before inclusion entrapment. Enriched, high-Ce/Y inclusions contain ∼300 ppm CO2, have low CO2/Nb (contents 50–100) and melts are likely to have exsolved much of their original CO2 contents prior to inclusion entrapment. The negative correlation between CO2 content and trace element enrichment may arise either from the more efficient exsolution of CO2 from enriched melts, or from the intrusion of CO2-supersaturated depleted melts into enriched melts that had already exsolved much of their original CO2 contents. Some inclusions have lower CO2 contents than predicted from binary mixing models, which suggests that at least some CO2 exsolution occurred concurrently with mixing. Enriched inclusions record entrapment pressures of ∼0.5 kbar. These pressures probably correspond to the depth of mixing. Higher pressures recorded in depleted inclusions may have resulted from the development of CO2 supersaturation during ascent from storage at ≥1.5 kbar. The presence of CO2 supersaturation in melt inclusions has the potential to constrain timescales of melt inclusion entrapment. [Copyright &y& Elsevier]

Electrically conductive polypropylene nanocomposites containing multi-walled carbon nanotubes were produced by melt blending by dilution of a concentrate masterbatch containing 10 wt.% of filler. In order to promote polymer infiltration within primary agglomerates a ultra-low melt viscosity polypropylene grade has been used for masterbatch production. Moreover, three polypropylenes with different melt viscosities have been used for successive dilutions. Filler dispersion has been assessed by both indirect macroscale analyses and direct morphological investigations. Characterization showed percolation thresholds occurring for very low filler contents. During dilution, lower polymer viscosities lead to more effective residue agglomerates dispersion, hence better electrical properties. [ABSTRACT FROM AUTHOR]

Abstract: The nature of magmatic sources reflected by isotopic composition of the ocean island basalt (OIB) remains an on-going question in igneous geochemistry. To constrain the magmatic sources for OIB related to the Kerguelen plume activity, we performed detailed microanalytical investigation of the 21.4Ma picritic basalt (MD109-D6-87) dredged during the “Marion Dufresne” cruise on a seamount between Kerguelen Archipelago and Heard Island. Lead isotope compositions of olivine-hosted melt inclusions and matrix glasses were measured by Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) and Secondary Ion Mass Spectrometry (SIMS). We also performed major and trace element microanalyses and mapping of the inclusions and the host olivine phenocrysts by electron microprobe (wavelength-dispersive X-ray spectroscopy, WDS). The observed significant major element (K2O/P2O5, Al2O3/TiO2) and Pb isotope (207Pb/206Pb and 208Pb/206Pb) heterogeneities of parental melts (MgO=7–10wt.%) during early high pressure crystallisation stage (200–300MPa, Fo82–86 mol%), and relative homogeneity at later lower-pressure crystallisation stage (<100MPa, Fo75–80 mol%) are interpreted by mixing between “Plume” and “Assimilant” melts during magma residence and transport. Lead isotope composition of the parental basaltic melts was inherited from both heterogeneous mantle and the Kerguelen Plateau crust. High K2O/P2O5 (>4), Al2O3/TiO2 (>4) ratios are attributed to assimilation of the plateau basaltic crust (≥50wt.%) by the melts in the magma chamber at palaeodepths from 6 to 9km. The crustal assimilation may have happened through plagioclase dissolution. The large chemical and isotopic heterogeneity of the parental OIB melts found by in situ microanalyses in this study suggests that the bulk rock chemistry alone cannot provide enough information to constrain the nature of the magmatic sources. [Copyright &y& Elsevier]

The relationship between varying processing variables, rotor speed (50 to 200 rpm) and mixing time (10 to 30 min), and MWCNT loading (0.5 to 2.0 wt%), on MWCNT dispersion in a poly(propylene) during batch melt mixing was investigated. MWCNT dispersion was improved by increasing rotor speed and/or mixing time, 200 rpm and 30 min being optimum, although composites prepared employing 100 rpm and 20 min were the most electrically conducting, (<100 S cm−1). PP shear viscosity increased with increasing MWCNT loading yielding a rheological percolation of ∼0.5 wt% MWCNTs. Volume resistivity of the composites decreased with increasing rotor speed and for mixing times up to 20 min only, the former yielding an electrical percolation of ∼0.65 wt% MWCNTs at 200 rpm. [ABSTRACT FROM AUTHOR]

Abstract: Platinum-group minerals are the dominant control on the budget of platinum-group elements in ophiolitic chromitites. They vary widely in distribution, morphology, chemistry and Os-isotope compositions. Their distribution in different types of chromitites, and different microstructural sites within them may reflect the role of chromite as a physical “collector” of the platinum-group elements during crystallisation of both phases from melts. The platinum-group minerals show significant Os-isotope heterogeneity on the scale of single micrometric grains enclosed within individual chromite grains. This micro-scale isotopic heterogeneity, and their random spatial distribution within the chromites, argue strongly against an origin of the platinum-group minerals via exsolution from the chromite lattice during post-magmatic cooling. A re-interpretation of their microstructures and Os isotopes analysed in situ had led us to review the traditional models, and to propose several origins for the platinum-group minerals in chromitites. (1) The suites of platinum-group minerals mainly record crystallisation during mixing of multiple different melts and physical entrapment in chromite. (2) Some platinum-group minerals in chromitites may have been scavenged from wall–rock peridotite during migration of the parental melts of the chromitite. (3) Other platinum-group minerals may have precipitated from metasomatic fluid/melts that infiltrated existing chromitites. The recrystallization of pre-existing platinum-group minerals during polyphase metamorphism or “recycling” of the chromitite into deeper mantle levels can explain the presence of micrometric platinum-group minerals with distinct Os-isotope compositions. [Copyright &y& Elsevier]

Late-orogenic Pan-African tectonics formed an 8km long fault-fracture zone in the shallow foreland crust of the Gariep Orogen in Mesoproterozoic granitoid basement. Pseudotachylyte was locally formed during a single seismic event that caused brittle failure in cohesive quartz-diorite, granodiorite and granitic gneiss. 40Ar/39Ar laser spot analysis provides an age of 512.5±7.5Ma for this seismic event. The depth of the hypocentre between 1700 and 5300m is inferred from the likely thickness of the overlying rock at that time. Abundant quartz melting in conjunction with low host rock temperature indicates a minimum seismic temperature rise exceeding 1030°C but in some samples dry quartz melting at temperatures exceeding 1700°C might have been possible. The abundance of hydrous phases in the host rock controlled the volume of melt produced in a given host rock type. Different types of primary melt were formed by the fusion of batches of host rock with different relative proportions of plagioclase, alkali feldspar, quartz, biotite, and, where present, amphibole or garnet. The chemical and physical interaction between these melts depended on contrasting melt mobility and viscosity. In quartz-diorite, glasses of variable composition are well preserved and show the distribution of primary melt species at the time of quenching. These different melt species had limited tendency of mixing, unless mixing was assisted by syn-seismic shearing. In granodiorite, which has a low proportion of hydrous phases, low-viscosity melt was formed at high temperatures, eliminating most host rock fragments and leading to extensive melting of quartz. The low melt viscosity, probably further decreased by the dissolution of free H2O, permitted effective melt homogenisation in such veins. Still in the liquid state these melts segregated, effectively separating secondary melts of sodic–calcic and of K–Mg–Fe-rich composition. After quenching the solid state diffusion of cations in glass was comparatively insignificant. [ABSTRACT FROM AUTHOR]

Abstract: The effect of plasticizer’s (PEG) molecular weight (MW) on PVP based solid dispersions (SDs), prepared by melt mixing, was evaluated in the present study using Tibolone as a poorly water soluble model drug. PEGs with MW of 400, 600, and 2000g/mol were tested, and the effect of drug content, time and temperature of melt mixing on the physical state of Tibolone, and the dissolution characteristics from SDs was investigated. PVP blends with PEG400 and PEG600 were completely miscible, while blends were heterogeneous. Furthermore, a single Tg recorded in all samples, indicating that Tibolone was dispersed in a molecular lever (or in the form of nanodispersions), varied with varying PEG’s molecular weight, melt mixing temperature, and drug content, while FTIR analysis indicated significant interactions between Tibolone and PVP/PEG matrices. All prepared solid dispersion showed long-term physical stability (18months in room temperature). The extent of interaction between mixture components was verified using Fox and Gordon–Taylor equations. Artificial neural networks, used to correlate the studied factors with selected dissolution characteristics, showed good prediction ability. [Copyright &y& Elsevier]

Current work explores the possibility of incorporating common commercial non-steroidal anti-inflammatory drugs (NSAIDs) into poly(propylene) in order to develop biocompatible and bioactive surgical implants/sutures with controlled release characteristics. More particularly, we attempted to incorporate Ibuprofen, a widely utilized NSAID, into isotactic poly(propylene) ( i-PP) films. Two basic methods of mixing were used and evaluated for their effectiveness; melt-mixing/melt-pressing and solvent casting. The produced films morphology as well as the nature of the incorporated drug was examined by Optical and Scanning Electron Microscopy (SEM/EDX). The drug release rates were measured by UV-Vis absorbance spectroscopy. [ABSTRACT FROM AUTHOR]

Poly(vinyl pyrrolidone) (PVP)/poloxamer-188 blends were used as appropriate carriers for the preparation of solid dispersions by hot melt extrusion using aripiprazole (ARIP) as a poor water-soluble model drug. The physical state of ARIP in solid dispersions and its dissolution characteristics were tested for different drug contents and various PVP-to-poloxamer ratios. From TG analysis it was found that all materials were stable at the tested extrusion temperature conditions (110-120 °C) while amorphous drug dispersions were prepared in all cases, due to the miscibility of the polymer matrix with ARIP drug. Furthermore, hydrogen bonds were identified between ARIP (>N-H) and PVP (>C=O) using FT-IR analysis. Finally, ARIP dissolution rate from SDs was pH dependant and increased as the drug content decreased. [ABSTRACT FROM AUTHOR]

Abstract: New shape-memory materials (SMMs) for applications in active control and morphing structures have been attracting special attention due to its unique properties. These SMM can be metallic alloys (SMAs), piezoelectric, and polymers such as polyurethanes (SMPUs). The latter detain higher recovery rates but better processability, however, the reaction time is longer when compared with the SMA. The addition of carbon nanotubes (CNTs) to SMPU seems to improve its overall properties with a great deal of potential in what concerns improved shape memory. There are two main techniques to attain SMPU/CNts nanocomposites: in situ polymerization and mechanical melt mixing. The study here presented establishes a comparison between these two techniques. To assess the suitability of the latter a rather extensive characterization was carried out. The homogeneity of the CNTs dispersion into the polymer matrix was established through SEM and the thermal characterization has shown a rise in the glass transition temperature consistent with CNT loading. Furthermore, shape memory seems to improve with the nanoparticle reinforcement. Within the two processing techniques it could be referred that melt processing seems to be simpler to use with better laboratory repeatability, thus detaining a greater potential should nanocomposite tailoring at a larger scale be envisaged. [Copyright &y& Elsevier]

Novel copolyesters have been prepared by melt mixing poly(ethylene terephthalate) (PET) with an ethoxylated bisphenol S, with the aim to prepare new polyesters with increased Tg, to be used in a wider range of temperatures with respect to neat PET. No side reactions occur during the synthesis of the samples, as proved by NMR analysis. The insertion of the bisphenol S (sulfonyldiphenol) groups does not significantly alter the thermal stability of PET. The thermal analysis showed that Tm and crystallization rate of the copolymers decreased with incasing co-unit content. The Tg of the copolyesters can be increased by bisphenol S insertion, up to 40°C higher with respect to neat PET, that allows the use of amorphous PET in a wider range of applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

The rheological behaviour of styrene-free unsaturated polyester resin-organoclay (Cloisite 15A) nanocomposites at various clay contents, prepared by melt mixing, was investigated. Styrene-free resin was used to achieve high-shear mixing and to avoid viscosity changes due to solvent evaporation. In order to compare the effects of shear- and diffusion-induced phenomena on the intercalation of nanoclay; samples were prepared at two different temperatures of 40 °C (cold-mixed) and 150 °C (hot-mixed) and tested in the range of 40-120 °C using dynamic rheometry. Complex viscosity-temperature curves for cold-mixed samples showed a decrease in viscosity with increasing temperature followed by the formation of a plateau at a particular temperature, depending on the clay content. This behaviour is characteristic of systems with a network structure. The results of small angle X-ray diffraction and TEM analysis confirmed the intercalation of the nanoclay particles as well as a reduction in their thickness. TEM images revealed that the size reduction happened through bending fracture followed by shear delamination of the fractured clay layers. On this basis, a structure of the physical network was proposed to be formed by sticking several nanoclay stacks inside a polymer chain and more involvement of polymer chains with the delaminated layers' ends. A dispersion model was used to quantify and interpret the dispersion status of nanoclay particles in the resin system. [ABSTRACT FROM AUTHOR]

Abstract: Three different heteroaromatic ring derivatives (coagents) were used to adjust the melt radical reaction of polypropylene (PP). From the results of high temperature 1H NMR and high-temperature size-exclusion chromatography (HT-SEC), all the coagents could quickly convert the tertiary PP macroradicals into resonance stabilized macroradicals and effectively restrain the β-scission of PP macroradicals. Long chain branched structures, without significant bimodal distribution of molecular weight, could be introduced into coagents-functionalized PP samples. Effect of chemical structures of heteroaromatic rings and electron-attracting groups on the molecular structures and melt properties of modified PP samples was studied. The possible reactions of coagents-functionalized PP samples in different theoretical molar ratio of coagent to alkoxy radical were also proposed according to the results of 1H NMR, torque curves, rheological measurements and HT-SEC coupled with laser light scattering detector. [Copyright &y& Elsevier]

The influence of melt-mixing parameters on the development of 'network-like' structure of multiwall carbon nanotubes (MWNTs) in injection-molded polypropylene (PP)/MWNTs composites was assessed through AC electrical conductivity measurements. A higher melt-mixing temperature (260°C as compared to 200, 220, and 240°C) at a fixed rotational speed of the screws (150 rpm) and at a fixed mixing time (15 min) has yielded maximum improvement in electrical conductivity in PP/MWNTs composites of 3 wt % MWNTs content. Next to higher melt-mixing temperature, a variation in the melt-mixing time has also led to a variation in electrical conductivity of the composites. Raman spectroscopic analysis revealed an increase in the ratio of intensity due to G-band over that of D-band ( I G/ I D) of the MWNTs in the 'skin' region as compared to the 'core' region of the injection-molded composites irrespective of the melt-mixing conditions. Microscopic observations could not provide much insight into the variation of MWNTs network-like structure in various PP/MWNTs composites. An attempt has been made to understand the variation of network-like structure of MWNTs in PP/MWNTs composites as a function of melt-mixing parameters through electrical conductivity measurements, Raman spectroscopic analysis, and morphological investigations. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Divinylbenzene (DVB) was used as a comonomer of styrene (St) during the preparation of polypropylene/polystyrene (PP/PS) nanoblends by diffusion and polymerization of St in isotactic PP pellets to make the PS domains crosslinked and further to reduce the coalescence of the PS domains during melt mixing. Different morphologies were obtained after melt mixing with different amounts of the initiator benzoyl peroxide (BPO) and DVB, which was explained by different morphology evolutions during melt mixing with different crosslinked structures of the PS chains. With relatively high amounts of BPO and DVB, the nanosized PS domains almost kept their shape and size, and only simple aggregates of a few PS particles with an average size of 130 nm were observed after melt mixing of the PP/PS blends. It can be concluded that DVB is useful for morphology stabilization of the PP/PS nanoblends during subsequent melt processing. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Processing, electrical, and electromagnetic interference (EMI) shielding behaviors of carbon nanotube (CNT)/acrylonitrile-butadiene-styrene (ABS) nanocomposites were studied as function of CNT concentration. The nanocomposites were prepared by melt mixing followed by compression molding. The selective and good level of dispersion of CNT in the styrene-acrylonitrile section of the ABS polymer was found to create conductive networks in the ABS matrix at a nanofiller loading of 0.75 wt %. At this nanofiller loading, the nanocomposite electrical conductivity was 10−5 S/m. This conductivity makes the nanocomposite suitable for electrostatic discharge protection applications. The EMI shielding effectiveness of the nanocomposites increased with the increase in nanofiller concentration. In the 100-1500 MHz frequency range, 1.1 mm thick plates made of ABS nanocomposite filled with 5 wt % CNT exhibit an EMI shielding effectiveness of 24 dB. At this shielding level, the nanocomposite is suitable for a broad range of applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 [ABSTRACT FROM AUTHOR]

Abstract: In the present study, the efficiency of PVP/PEG200 mixtures as appropriate carries for the preparation of solid dispersions by melt mixing was evaluated. Felodipine (FELO) was used as a poorly water soluble model drug. The effect of several melt mixing parameters, (PVP/PEG ratio, time and temperature of melt mixing, and drug content), on the physical state of FELO and the dissolution characteristics of the dispersions were investigated. DSC, XRD, and SEM analysis revealed that in all cases, amorphous drug nanodispersions were prepared. This was attributed to the increased miscibility of the PVP–FELO system, induced by the presence of PEG200, which acted as plasticizer. FT-IR analysis showed hydrogen bonding between FELO (h name="sbnd" />H) and the PVP carrier (h name="dbnd" />O). The release rate of the drug depends mainly on the drug content and is higher in solid dispersions with low drug content and ratio of carrier to plasticizer (PVP/PEG200). The melt mixing variations (time and temperature of mixing) had lower impact on FELO release rate. Finally, artificial neural networks, used to correlate the examined formulation and process variables of hot melt mixing with dissolution parameters, showed good prediction ability. [Copyright &y& Elsevier]

Abstract: A new on-line optical sensor based on light scattering, dedicated to real-time monitoring during processing of polymer blends and polymer nanocomposites, has been used to characterize dispersion and morphology of polypropylene based organoclay nanocomposites. Polypropylene matrix was mixed with various concentration of organo modified montmorillonite. The results given by optical measurements were compared to those of XRD, TEM and rheological characterizations. The results showed that the transmitted light intensity increases with increasing extent of exfoliation. At high filler concentration, the optical sensor allows a qualitative characterization of the nanocomposite morphology. [Copyright &y& Elsevier]

This work aims to investigate the dynamic behavior of polypropylene organoclay nanocomposites. The nanocomposite was obtained by mixing the polypropylene matrix with a masterbatch of polypropylene modified anhydride maleic and montmorillonite organoclay (pp-nanocor). The dynamic behavior was investigated by using split Hopkinson pressure bars, at different strain rates and different temperatures. The obtained nanocomposite exhibits a good dispersion and a partially exfoliated morphology. To study the effect of nanocomposite dispersion and morphology on the dynamic behavior, another nanocomposite was prepared by melt mixing of polypropylene and a modified montmorillonite (dellite) (PP dellite). The dynamic property results for PP-nanocor show an increase of both Young's modulus and yield stress with the increasing organoclay concentration. However, PP-dellite nanocomposites present poor mechanical properties compared with those of PP-nanocor. [ABSTRACT FROM AUTHOR]

Melt mixing with a polymer is a novel strategy to modify the surface property of carbon nanotube (CNT) conveniently and efficiently. In melt mixing process, the shearing and thermal issues can make polymer component wrapped around nanotubes via π-π stacking interaction. In this study, polystyrene-coated multi-walled carbon nanotubes (MWNTs) was achieved through simple melt mixing of polystyrene with MWNTs. PS and MWNTs were first melt mixed at various melt time and temperatures to find the optimum condition for preparing of PS-coated MWNTs. Subsequently, the stability of polystyrene interacted with MWNTs was estimated via ultrasonication and thermal gravimetric analysis (TGA). Finally, the physically modified MWNTs were used to enhance polystyrene. An obvious mechanical reinforcement can be achieved, which approves a huge potential of application of these modified MWNTs in practical composite products. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: This study establishes and compares structure–property–processing relationships on three drug delivery systems containing an anionic active pharmaceutical ingredient (API) in the following excipient carriers: (a) an inorganic anionic nanoclay, (b) pH responsive acrylic polymers, and (c) combinations thereof. The effects of the excipients on the APIs dissolution rate were studied from their release profile in simulated body fluids (SBFs) with different pH. In the API-nanoclay system, calcination of the clay followed by its reconstitution in an API solution was successfully used to intercalate the API in its amorphous state in the clay. As a result, the API showed increased apparent solubility vs. its crystalline form with its release mechanism from the clay being predominantly diffusion controlled and depending on the pH of the SBFs. In melt mixed ternary polymer systems containing the above hybrids, as a result of an additional diffusional step due to presence of nanoplatelets, the API showed a more controlled release vs. polymer systems that contained only API. By comparison to the low pH SBF, the ternary system in the pH 7.4 SBF showed a reduced diffusion contribution due to the presence of clay platelets, the latter unaffected by the high pH value. Reasonable agreement was found with predictions from literature diffusion/erosion models. It is confirmed that hot melt mixing offers opportunities to produce systems with enhanced API apparent solubility. The presence of nanoclays can also increase the API''s apparent solubility and affect its release in a controlled manner. [Copyright &y& Elsevier]