Structure,thermal stability,and mechanical properties of nanocomposites based on an amorphous polyamide

Polymer nanocomposites based on an amorphous polyamide (aPA) modified with three organoclays were obtained in the melt state. The observed T_g decreases indicated that some organic modifier of the OMMT (surfactant) migrated to the matrix during mixing. The decrease in the thermal stability of the aPA in nitrogen atmosphere on organoclay addition was attributed to the instability of the organoclays. The smaller decrease in the thermal stability of the nanocomposites in air atmosphere was attributed to a barrier effect. The largest dispersion (an average of only 1.2 layers per particle) occurred using the octadecylamine‐modified organoclay (I30) that has the maximum uncovered surface; this indicates the basic importance of this parameter on exfoliation. Despite the bulky nature of the aPA that hinders the matrix/inorganic surface interactions, this dispersion level is comparable to that of semicrystalline polyamides with similar polarity. This indicates that the relation between high polarity of the matrix and high dispersion level also works in bulky aPAs, as that of this study. The significant modulus increases (56% for the nanocomposite with 5% I30) are consistent with the measured high dispersion level. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Effect of blending ratio and catalyst loading on co-gasification of wood chips and coconut waste

Catalytic co-gasification is an important tar reforming technique, which may appreciably improve the quality of syngas through tar reforming reaction. In this study, wood chips (WC) were co-gasified with two coconut wastes, namely coconut shells (CS) and coconut fronds (CF), in a downdraft gasifier. The dolomite and limestone were used as tar reforming mediums. The effect of the blending ratio, catalyst type, biomass type and catalyst to biomass loading on gas composition and heating value of the syngas was investigated for different WC/CS and WC/CF blends. The results revealed that the WC/CS blending ratio of 70:30 produces the highest H₂ amount (11.70 vol.%), which was 31% higher than the H₂ amount of the other blends. The HHV_syngas of 70:30 blend was measured about 4.96 MJ/Nm³, which was also higher among all the tested blends. The co-gasification of 70:30 blend of WC/CS, when compared with same blending ratio WC/CF, produced two times higher CO, 60% higher H₂ and 75% higher HHV_syngas. During catalytic co-gasification of WC/CS blends with dolomite and limestone, the dolomite yielded 24%, 13.8% and 25.6% increment in CO, H₂, and CH₄, respectively. It is concluded that the coconut wastes can be substituted or co-gasified with wood after carrying out some major changes in a gasifier geometry.     

Analysis of the essential work of fracture method as applied to UHMWPE

The validity of the basic assumptions behind the method of essential work of fracture (EWF), as applied to ultra-high molecular weight polyethylene (UHMWPE), is evaluated using finite element modelling. To define a suitable model of constitutive behaviour, the mechanical properties of UHMWPE have been measured in both uniaxial tension and compression over a range of strain rates. The observed strain rate dependence of stress, including the observed differences in strain rate sensitivity between tension and compression, is interpreted in terms of a single Eyring process. The constitutive theory is constructed comprising an Eyring process and hyperelastic networks, the latter having responses symmetric with respect to tension and compression. This theory is implemented within a finite element scheme, and used to model fracture measurements made on the same material using double-edge notch tensile specimens. Calculations of the non-essential work and of the extent of the plastic zones are thus made possible. It is concluded that the specific non-essential work is essentially constant, but that the shape factor β, assumed constant in the conventional analysis, varies significantly with ligament length. The implication of this finding on the derived EWF value is evaluated and found to be slight.     

Structure and mechanical properties of blends of poly(ε‐caprolactone) with a poly(amino ether)

Poly(ε‐caprolactone) (PCL)/poly(amino ether) (PAE) blends were obtained by injection molding without any previous extrusion step in an attempt to (i) contribute to the knowledge of the relation between structure and mechanical properties in these type of blends composed of a rubbery and a glassy polymer and (ii) to find out to which extent are the PCL/PAE blends compatible, and therefore whether the biodegradability of PCL can be added as a characteristic of PAE‐based applications. PCL/PAE blends are composed of a crystalline PCL phase, a pure amorphous PCL phase, and a PAE‐rich phase where some PCL is present. The presence of some dissolved and probably unreacted PCL in the PAE‐rich phase led to a low interfacial tension as observed by the small size of the dispersed particles and the large interfacial area. The dependence on composition of both the modulus of elasticity and the yield stress of the blends was parallel to that of the orientation level. The elongation at break showed values similar to those of PAE in PAE‐rich blends, and was slightly synergistic in very rich PCL compositions; this behavior reflects a change in the nature of the matrix, from glassy to rubbery. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nonlinear Decentralized Feedback Linearizing Controller Design for Islanded DC Microgrids

This paper aims to design decentralized controllers for different components in islanded DC microgrids. The major components in the DC microgrid as considered in this paper include a fuel cell, solar photovoltaic (PV) unit, and battery energy storage system (BESS) along with critical and non-critical loads. The main control objective is to maintain the power balance within the DC microgrid through the regulation of the common DC-bus voltage. The controllers are designed based on the dynamical models of the fuel cell, solar PV unit, and BESS. The feedback linearization technique is employed to obtain the control laws, which simplifies the original dynamical models and decouples different components in the form of several subsystems. In this way, the feedback linearization technique allows different components in DC microgrids to achieve the desired control objectives by using only the local information (i.e., in a decentralized manner). The performance of the proposed decentralized controllers for different components is evaluated on a test DC microgrid under different operating conditions. Simulation results demonstrate that the proposed control scheme performs in a much better way as compared to an existing proportional integral controller.     

Chemical composition and antimicrobial activity of Anzer tea essential oil

Anzer tea (Thymus praecox, subsp. caucasicus var. caucasicus) naturally grows in the eastern Black Sea region of Turkey. Anzer tea, a creeping plant with crimson‐pink flowers, is important for honey production in the region. In the present study, content, composition and antimicrobial properties of Anzer tea's essential oil were investigated. Essential oil content of dried aerial plant parts varied between 1.53% and 2.05%. Essential oil composition was studied by means of gas chromatography–mass spectrometry, and 26 components were identified. The major components were thymol (47.45%), γ‐terpinene (8.73%), p‐cymene (8.30%), terpinyl acetate (4.88%) and carvacrol (4.66%). Essential oil was also screened for its antibacterial activity. In a screen for antibacterial activity, Anzer tea essential oil had significant activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Candida albicans. Copyright © 2007 Society of Chemical Industry     

Recent Developments in Nanomaterials-Based Drug Delivery and Upgrading Treatment of Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading causes of morbidity and mortality worldwide. However, despite the recent developments in the management of CVDs, the early and long outcomes vary considerably in patients, especially with the current challenges facing the detection and treatment of CVDs. This disparity is due to a lack of advanced diagnostic tools and targeted therapies, requiring innovative and alternative methods. Nanotechnology offers the opportunity to use nanomaterials in improving health and controlling diseases. Notably, nanotechnologies have recognized potential applicability in managing chronic diseases in the past few years, especially cancer and CVDs. Of particular interest is the use of nanoparticles as drug carriers to increase the pharmaco-efficacy and safety of conventional therapies. Different strategies have been proposed to use nanoparticles as drug carriers in CVDs; however, controversies regarding the selection of nanomaterials and nanoformulation are slowing their clinical translation. Therefore, this review focuses on nanotechnology for drug delivery and the application of nanomedicine in CVDs.     

Effect of Ethylene Flow Rate and CVD Process Time on Diameter Distribution of MWCNTs

To date, focus of the research activities in nanoscience was to control the chemical vapor deposition (CVD) growth of carbon nanotubes (CNTs) by changing the precursor pressure and process temperature. The effect of the precursor flow rate and process time on CNTs growth parameters has been overlooked in past studies and therefore is very little known. This study was focused on the optimization of the ethylene flow rate and CVD process time for CNTs growth over Fe₂O₃/Al₂O₃ catalyst in a fluidized bed chemical vapor deposition (FBCVD) reactor, operating at atmospheric pressure. Argon and hydrogen were considered as the carrier and supporting gases, respectively. Transmission electron microscope (TEM) and Scanning Electron Microscopy (SEM) were used to investigate the surface morphology, nanostructures, purity and yield of the grown CNTs. In-depth analysis revealed an increase in tube length, yield and the carbon concentration with ethylene flow rate in the range of 50–110 sccm. However, an inverse relationship between flow rate and tube diameter distribution was predicted in the given work. The most favorable results were obtained at an ethylene flow rate of 100 sccm and a CVD process time of 60 minutes. The dense and homogeneous growth of relatively pure nanotubes of increased tube length and narrow diameter distribution, in the range of 20–25 nm, was observed at optimized flow rate and process time.