bluuebunny/crossref_metadata_2025 huggingface dataset:
Natural Compounds as Sustainable Additives for Biopolymers
Authors: Dintcheva Nadka Tzankova , Infurna Giulia , Baiamonte Marilena , D’Anna Francesca
Published: April 2020

In the last few decades, the interest towards natural compounds, coming from a natural source and biodegradable, for biopolymers is always increasing because of a public request for the formulation of safe, eco-friendly, and sustainable materials. The main classes of natural compounds for biopolymers are: (i) naturally occurring fillers (nFil), such as nano-/micro- sized layered alumino-silicate: halloysite, bentonite, montmorillonite, hydroxyapatite, calcium carbonate, etc.; (ii) naturally occurring fibers (nFib), such as wood and vegetable fibers; (iii) naturally occurring antioxidant molecules (nAO), such as phenols, polyphenols, vitamins, and carotenoids. However, in this short review, the advantages and drawbacks, considering naturally occurring compounds as safe, eco-friendly, and sustainable additives for biopolymers, have been focused and discussed briefly, even taking into account the requests and needs of different application fields.
Influence of Manufacturing Parameters and Post Processing on the Electrical Conductivity of Extrusion-Based 3D Printed Nanocomposite Parts
Authors: Paz Rubén , Moriche Rocío , Monzón Mario , García Joshua
Published: April 2020

The influence of manufacturing parameters of filament extrusion and extrusion-based Additive Manufacturing (AM), as well as different post processing techniques, on the electrical conductivity of 3D printed parts of graphene nanoplatelets (GNP)-reinforced acrylonitrile butadiene styrene (ABS) has been analyzed. The key role of the manufacturing parameters to obtain electrically conductive filaments and 3D printed parts has been demonstrated. Results have shown that an increase in extrusion speed, as well as lower land lengths, induces higher extrudate swelling, with the consequent reduction of the electrical conductivity. Additionally, filaments with lower diameter values, which result in a higher surface-to-cross-section ratio, have considerably lower electrical conductivities. These factors tune the values of the volume and surface electrical conductivity between 10−4–100 S/m and 10−8–10−3 S/sq, respectively. The volume and surface electrical conductivity considerably diminished after 3D printing. They increased when using higher printing layer thickness and width and were ranging between 10−7–10−4 S/m and 10−8–10−5 S/sq, respectively. This is attributed to the higher cross section area of the individual printed lines. The effect of different post processing (acetone vapor polishing, plasma and neosanding, which is a novel finishing process) on 3D printed parts in morphology and surface electrical conductivity was also analyzed.
Modeling of Stripe Patterns in Photosensitive Azopolymers
Authors: Yadav Bharti , Domurath Jan , Saphiannikova Marina
Published: April 2020

Placed at interfaces, azobenzene-containing materials show extraordinary phenomena when subjected to external light sources. Here we model the surface changes induced by one-dimensional Gaussian light fields in thin azopolymer films. Such fields can be produced in a quickly moving film irradiated with a strongly focused laser beam or illuminating the sample through a cylindrical lens. To explain the appearance of stripe patterns, we first calculate the unbalanced mechanical stresses induced by one-dimensional Gaussian fields in the interior of the film. In accordance with our orientation approach, the light-induced stress originates from the reorientation of azobenzenes that causes orientation of rigid backbone segments along the light polarization. The resulting volume forces have different signs and amplitude for light polarization directed perpendicular and parallel to the moving direction. Accordingly, the grooves are produced by the stretching forces and elongated protrusions by the compressive forces. Implementation into a viscoplastic model in a finite element software predicts a considerably weaker effect for the light polarized along the moving direction, in accordance with the experimental observations. The maximum value in the distribution of light-induced stresses becomes in this case very close to the yield stress which results in smaller surface deformations of the glassy azopolymer.
High-Contrast and Scattering-Type Transflective Liquid Crystal Displays Based on Polymer-Network Liquid Crystals
Authors: Liu Cheng-Kai , Chen Wei-Hsuan , Li Chung-Yu , Cheng Ko-Ting
Published: April 2020

The methods to enhance contrast ratios (CRs) in scattering-type transflective liquid crystal displays (ST-TRLCDs) based on polymer-network liquid crystal (PNLC) cells are investigated. Two configurations of ST-TRLCDs are studied and are compared with the common ST-TRLCDs. According to the comparisons, CRs are effectively enhanced by assembling a linear polarizer at the suitable position to achieve better dark states in the transmissive and reflective modes of the reported ST-TRLCDs with the optimized configuration, and its main trade-off is the loss of brightness in the reflective modes. The PNLC cell, which works as an electrically switchable polarizer herein, can be a PN-90° twisted nematic LC (PN-90° TNLC) cell or a homogeneous PNLC (H-PNLC) cell. The optoelectric properties of PN-90° TNLC and those of H-PNLC cells are compared in detail, and the results determine that the ST-TRLCD with the optimized configuration using an H-PNLC cell can achieve the highest CR. Moreover, no quarter-wave plate is used in the ST-TRLCD with the optimized configuration, so a parallax problem caused by QWPs can be solved. Other methods for enhancing the CRs of the ST-TRLCDs are also discussed.
Effect of Stabilizer States (Solid Vs Liquid) on Properties of Stabilized Natural Rubbers
Authors: Promhuad Khwanchat , Smitthipong Wirasak
Published: April 2020

The main objective of this work is to study the effect of hydroxylamine sulfate or stabilizer states (solid vs liquid) on the storage hardening of natural rubber (NR). Several types of natural rubber samples were prepared: unstabilized NR samples and stabilized NR samples: (i) dry NR with 0.2 and 2.0 parts per hundred rubber (phr) of dry hydroxylamine sulfate, and (ii) natural latex with 0.2 and 2.0 phr of liquid hydroxylamine sulfate. The samples were characterized immediately (time 0) and after 12 weeks of storage at room temperature, respectively. We found that the Mooney viscosity, gel content, and Wallace plasticity of NR without a stabilizer increases with storage hardening for 12 weeks. However, two types of stabilized NR samples represent constant values of those three parameters, because hydroxylamine sulfate inhibits network and gel formation in NR. Interestingly, the mixing states (solid vs liquid) between natural rubber and the stabilizer affect the properties of stabilized NR. This could be explained by the better dispersion and homogeneous nature of liquid stabilizers in natural latex (liquid state), and thus the higher loading of the stabilizer in the liquid state. This is important, as the stabilization of NR properties as a function of time is required by rubber industry. This study is a utilization model from theory to application.
Influence of Nanoparticles on Thermal and Electrical Conductivity of Composites
Authors: Coetzee Divan , Venkataraman Mohanapriya , Militky Jiri , Petru Michal
Published: April 2020

This review analyzes thermal and electrically conductive properties of composites and how they can be influenced by the addition of special nanoparticles. Composite functional characteristics—such as thermal and electrical conductivity, phase changes, dimensional stability, magnetization, and modulus increase—are tuned by selecting suitable nanoparticle filler material. The conductivity of composites can be related to the formation of conductive pathways as nanofiller materials form connections in the bulk of a composite matrix. With increasing use of nanomaterial containing composites and relatively little understanding of the toxicological effects thereof, adequate disposal and recyclability have become an increasing environmental concern.
Hybrid Lead-Halide Polyelectrolytes as Interfacial Electron Extraction Layers in Inverted Organic Solar Cells
Authors: Lee Jin Hee , Park Yu Jung , Seo Jung Hwa , Walker Bright
Published: April 2020

A series of lead-halide based hybrid polyelectrolytes was prepared and used as interfacial layers in organic solar cells (OSCs) to explore their effect on the energy band structures and performance of OSCs. Nonconjugated polyelectrolytes based on ethoxylated polyethylenimine (PEIE) complexed with PbX2 (I, Br, and Cl) were prepared as polymeric analogs of the perovskite semiconductors CH3NH3PbX3. The organic/inorganic hybrid composites were deposited onto Indium tin oxide (ITO) substrates by solution processing, and ultraviolet photoelectron spectroscopy (UPS) measurements confirmed that the polyelectrolytes allowed the work function of the substrates to be controlled. In addition, X-ray photoelectron spectroscopy (XPS) results showed that Pb(II) halide complexes were present in the thin film and that the Pb halide species did not bond covalently with the cationic polymer and confirmed the absence of additional chemical bonds. The composite ratio of organic and inorganic materials was optimized to improve the performance of OSCs. When PbBr2 was complexed with the PEIE material, the efficiency increased up to 3.567% via improvements in open circuit voltage and fill factor from the control device (0.3%). These results demonstrate that lead-halide based polyelectrolytes constitute hybrid interfacial layers which provide a novel route to control device characteristics via variation of the lead halide composition.
Preparation, Characterization of Propargyl Terminal Polybutadiene and Its Crosslinked Elastomers Properties
Authors: Zhai Jinxian , Guo Xiaoyan , Liu Nana
Published: April 2020

Propargyl terminal Polybutadiene (PTPB) was successfully prepared through hydroxyl terminal polybutadiene (HTPB) end-capping modification. The FTIR and 13C NMR results indicated that the HTPB terminal hydroxyl was thoroughly replaced and yielded the target product, PTPB, with a theoretical propargyl content of 0.66 mmol g−1. In comparison with HTPB, PTPB has a lower viscosity. Using 1,6-diazide hexane as a curing agent, polytriazole crosslinked polybutadiene (PTriPB) elastomers with various functional molar ratios (R) were prepared by CuAAC reaction, and the glass transition temperatures of the resultant PTriPB elastomers were approximately −75 °C, measured by differential scanning calorimetry (DSC), nearly independent of elastomer R values. Mechanical tests indicated, that with the increase in R, the mechanical properties of PTriPB elastomers exhibit a parabolic dependence on R. In addition, the thermal stability of PTriPB elastomers were also studied. The findings revealed some fundamental features of polytriazole crosslinking elastomer prepared by CuAAC reaction.
Preparation and Characterization of Condensed Tannin Non-Isocyanate Polyurethane (NIPU) Rigid Foams by Ambient Temperature Blowing
Authors: Chen Xinyi , Xi Xuedong , Pizzi Antonio , Fredon Emmanuel , Zhou Xiaojian , Li Jinxing , Gerardin Christine , Du Guanben
Published: April 2020

Ambient temperature self-blowing mimosa tannin-based non-isocyanate polyurethane (NIPU) rigid foam was produced, based on a formulation of tannin-based non-isocyanate polyurethane (NIPU) resin. A citric acid and glutaraldehyde mixture served as a blowing agent used to provide foaming energy and cross-link the tannin-derived products to synthesize the NIPU foams. Series of tannin-based NIPU foams containing a different amount of citric acid and glutaraldehyde were prepared. The reaction mechanism of tannin-based NIPU foams were investigated by Fourier Trasform InfraRed (FT-IR), Matrix Assisted Laser Desorption Ionization (MALDI-TOF) mass spectrometry, and 13C Nuclear Magnetic Resonance (13C NMR). The results indicated that urethane linkages were formed. The Tannin-based NIPU foams morphology including physical and mechanical properties were characterized by mechanical compression, by scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). All the foams prepared showed a similar open-cell morphology. Nevertheless, the number of cell-wall pores decreased with increasing additions of glutaraldehyde, while bigger foam cells were obtained with increasing additions of citric acid. The compressive mechanical properties improved with the higher level of crosslinking at the higher amount of glutaraldehyde. Moreover, the TGA results showed that the tannin-based NIPU foams prepared had similar thermal stability, although one of them (T-Fs-7) presented the highest char production and residual matter, approaching 18.7% at 790 °C.
Dynamic Heterogeneity in Ring-Linear Polymer Blends
Authors: Katsarou Anna , Tsamopoulos Alexandros , Tsalikis Dimitrios , Mavrantzas Vlasis
Published: April 2020

We present results from a direct statistical analysis of long molecular dynamics (MD) trajectories for the orientational relaxation of individual ring molecules in blends with equivalent linear chains. Our analysis reveals a very broad distribution of ring relaxation times whose width increases with increasing ring/linear molecular length and increasing concentration of the blend in linear chains. Dynamic heterogeneity is also observed in the pure ring melts but to a lesser extent. The enhanced degree of dynamic heterogeneity in the blends arises from the substantial increase in the intrinsic timescales of a large subpopulation of ring molecules due to their involvement in strong threading events with a certain population of the linear chains present in the blend. Our analysis suggests that the relaxation dynamics of the rings are controlled by the different states of their threading by linear chains. Unthreaded or singly-threaded rings exhibit terminal relaxation very similar to that in their own melt, but multiply-threaded rings relax much slower due to the long lifetimes of the corresponding topological interactions. By further analyzing the MD data for ring molecule terminal relaxation in terms of the sum of simple exponential functions we have been able to quantify the characteristic relaxation times of the corresponding mechanisms contributing to ring relaxation both in their pure melts and in the blends, and their relative importance. The extra contribution due to ring-linear threadings in the blends becomes immediately apparent through such an analysis.
Comparative Investigation on the Soil Burial Degradation Behaviour of Polymer Films for Agriculture before and after Photo-Oxidation
Authors: La Mantia Francesco , Ascione Laura , Mistretta Maria , Rapisarda Marco , Rizzarelli Paola
Published: April 2020

Polymer films based on biodegradable polymers, polyethylene (PE) and modified PE with oxo-degradable additive were prepared by film blowing. Carbon black (1%) was added to all the films. Commercial biodegradable Ecovio® and Mater-Bi® samples were used. Mechanical properties, soil burial degradation and surface wettability were investigated, before and after UV irradiation. Chemical modifications induced by UV and soil degradation, or a synergic effect, were highlighted by Attenuated Total Reflection-Fourier Transform Infra-Red (ATR-FTIR). Photo-oxidized film samples with an elongation at break equal to 50% and 0.5 the initial value were selected for the soil burial degradation test at 30 °C. Weight loss measurements were used to follow biodegradation in soil. Predictably, the degradation in soil was higher for biodegradable polymer-based films than for the PE-based ones. UV irradiation increased surface wettability and encouraged the disintegration in soil of all the samples. In fact, photo-oxidation produced a molar mass reduction and hydrophilic end groups, thus increasing surface erosion and weight loss. This paper not only supplies new criteria to evaluate the performance of biodegradable films in agriculture, before and after lifetime, but also provides a comparative analysis on the soil burial degradation behaviour with traditional ones.
Synergistic Effect of Maleated Natural Rubber and Modified Palm Stearin as Dual Compatibilizers in Composites based on Natural Rubber and Halloysite Nanotubes
Authors: Hayeemasae Nabil , Sensem Zareedan , Surya Indra , Sahakaro Kannika , Ismail Hanafi
Published: April 2020

The performance of rubber composite relies on the compatibility between rubber and filler. This is specifically of concern when preparing composites with very different polarities of the rubber matrix and the filler. However, a suitable compatibilizer can mediate the interactions. In this study, composites of natural rubber (NR) with halloysite nanotubes (HNT) were prepared with maleated natural rubber (MNR) and modified palm stearin (MPS) as dual compatibilizers. The MPS dose ranged within 0.5–1.5 phr, while the MNR dose was fixed at 10 phr in all formulations. It was found that the mixed MNR/MPS significantly enhanced modulus, tensile strength, and tear strength of the composites. The improvements were mainly due to improved rubber-HNT interactions arising from hydrogen bonds formed in the presence of these two compatibilizers. This was clearly verified by observing the Payne effect. Apart from that, the MPS also acted as a plasticizer to provide improved dispersion of HNT. It was clearly demonstrated that MNR and MPS as dual compatibilizers improved rubber-HNT interactions and reduced filler-filler interactions, which then improved tensile and tear strengths, as well as dynamical properties. Therefore, the mix of MNR and MPS had a great potential to compatibilize non-polar rubber with HNT filler.
Antiplasticization of Polymer Materials: Structural Aspects and Effects on Mechanical and Diffusion-Controlled Properties
Authors: Mascia Leno , Kouparitsas Yannis , Nocita Davide , Bao Xujin
Published: April 2020

Antiplasticization of glassy polymers, arising from the addition of small amounts of plasticizer, was examined to highlight the developments that have taken place over the last few decades, aiming to fill gaps of knowledge in the large number of disjointed publications. The analysis includes the role of polymer/plasticizer molecular interactions and the conditions leading to the cross-over from antiplasticization to plasticization. This was based on molecular dynamics considerations of thermal transitions and related relaxation spectra, alongside the deviation of free volumes from the additivity rule. Useful insights were gained from an analysis of data on molecular glasses, including the implications of the glass fragility concept. The effects of molecular packing resulting from antiplasticization are also discussed in the context of physical ageing. These include considerations on the effects on mechanical properties and diffusion-controlled behaviour. Some peculiar features of antiplasticization regarding changes in Tg were probed and the effects of water were examined, both as a single component and in combination with other plasticizers to illustrate the role of intermolecular forces. The analysis has also brought to light the shortcomings of existing theories for disregarding the dual cross-over from antiplasticization to plasticization with respect to modulus variation with temperature and for not addressing failure related properties, such as yielding, crazing and fracture toughness.
Dendritic Scaffold onto Titanium Implants. A Versatile Strategy Increasing Biocompatibility
Authors: Molina Noemi , González Ana , Monopoli Donato , Mentado Belinda , Becerra José , Santos-Ruiz Leonor , Vida Yolanda , Perez-Inestrosa Ezequiel
Published: April 2020

Osseointegration of metal prosthetic implants is a yet unresolved clinical need that depends on the interplay between the implant surface and bone cells. The lack of a relationship between bone cells and metal has traditionally been solved by coating the former with “organic” ceramics, such as hydroxyapatite. A novel approach is hereby presented, immobilizing covalently dendrimeric structures onto titanium implants. Amide-based amino terminal dendrons were synthetized and coupled to titanium surfaces in a versatile and controlled way. The dendritic moieties provide an excellent scaffold for the covalent immobilization of bioactive molecules, such as extracellular matrix (ECM) protein components or antibiotics. Herein, tripeptide arginine-glycine-aspartic acid (RGD) motifs were used to decorate the dendritic scaffolds and their influence on cell adhesion and proliferation processes was evaluated.
PET Fibers Modified with Cloisite Nanoclay
Authors: Fabia Janusz , Gawłowski Andrzej , Rom Monika , Ślusarczyk Czesław , Brzozowska-Stanuch Anna , Sieradzka Marta
Published: April 2020

The alternative method of reducing the flammability of polyethylene terephthalate (PET) fibers, analogous to dyeing of PET fibers with dispersed dyes in a high-temperature bath, was proposed. A commercial organophilic montmorillonite Cloisite®15A (C15A) was applied as a flame retardant. The aim of the presented work was to evaluate the effectiveness of the introduced modifier and the improvement of the flame-retardant properties of PET fibers by limiting oxygen index (LOI) and thermogravimetric analysis (TGA) measurements. Evolved gas analysis (EGA) by spectrometric method (FTIR) during coupled thermogravimetric analysis (TGA) was applied in order to confirm no increase in the toxicity of volatile degradation products released from burning modified fibers. The nanocomposite nature of modified fibers was confirmed based on the structural parameters of the fibers determined using wide-angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS) X-ray diffraction methods.
Bio-Based Polymers for Engineered Green Materials
Authors: Tondi Gianluca , Schnabel Thomas
Published: April 2020

Every [...]
512-Channel Geometric Droplet-Splitting Microfluidic Device by Injection of Premixed Emulsion for Microsphere Production
Authors: Kim Chul Min , Choi Hye Jin , Kim Gyu Man
Published: April 2020

We present a 512-channel geometric droplet-splitting microfluidic device that involves the injection of a premixed emulsion for microsphere production. The presented microfluidic device was fabricated using conventional photolithography and polydimethylsiloxane casting. The fabricated microfluidic device consisted of 512 channels with 256 T-junctions in the last branch. Five hundred and twelve microdroplets with a narrow size distribution were produced from a single liquid droplet. The diameter and size distribution of prepared micro water droplets were 35.29 µm and 8.8% at 10 mL/h, respectively. Moreover, we attempted to prepare biocompatible microspheres for demonstrating the presented approach. The diameter and size distribution of the prepared poly (lactic-co-glycolic acid) microspheres were 6.56 µm and 8.66% at 10 mL/h, respectively. To improve the monodispersity of the microspheres, we designed an additional post array part in the 512-channel geometric droplet-splitting microfluidic device. The monodispersity of the microdroplets prepared with the microfluidic device combined with the post array part exhibited a significant improvement.
Fabrication of PCL Scaffolds by Supercritical CO2 Foaming Based on the Combined Effects of Rheological and Crystallization Properties
Authors: Song Chaobo , Luo Yunhan , Liu Yankai , Li Shuang , Xi Zhenhao , Zhao Ling , Cen Lian , Lu Eryi
Published: April 2020

Polycaprolactone (PCL) scaffolds have recently been developed via efficient and green supercritical carbon dioxide (scCO2) melt-state foaming. However, previously reported gas-foamed scaffolds sometimes showed insufficient interconnectivity or pore size for tissue engineering. In this study, we have correlated the thermal and rheological properties of PCL scaffolds with their porous morphology by studying four foamed samples with varied molecular weight (MW), and particularly aimed to clarify the required properties for the fabrication of scaffolds with favorable interconnected macropores. DSC and rheological tests indicate that samples show a delayed crystallization and enhanced complex viscosity with the increasing of MW. After foaming, scaffolds (27 kDa in weight-average molecular weight) show a favorable morphology (pore size = 70–180 μm, porosity = 90% and interconnectivity = 96%), where the lowest melt strength favors the generation of interconnected macropore, and the most rapid crystallization provides proper foamability. The scaffolds (27 kDa) also possess the highest Young’s modulus. More importantly, owing to the sufficient room and favorable material transportation provided by highly interconnected macropores, cells onto the optimized scaffolds (27 kDa) perform vigorous proliferation and superior adhesion and ingrowth, indicating its potential for regeneration applications. Furthermore, our findings provide new insights into the morphological control of porous scaffolds fabricated by scCO2 foaming, and are highly relevant to a broader community that is focusing on polymer foaming.
Porous Ultra-Thin Films from Photocleavable Block Copolymers: In-Situ Degradation Kinetics Study of Pore Material
Authors: Altinpinar Sedakat , Ali Wael , Schuchardt Patrick , Yildiz Pinar , Zhao Hui , Theato Patrick , Gutmann Jochen S.
Published: April 2020

On the basis of the major application for block copolymers to use them as separation membranes, lithographic mask, and as templates, the preparation of highly oriented nanoporous thin films requires the selective removal of the minor phase from the pores. In the scope of this study, thin film of polystyrene-block-poly(ethylene oxide) block copolymer with a photocleavable junction groups based on ortho-nitrobenzylester (ONB) (PS-hν-PEO) was papered via the spin coating technique followed by solvent annealing to obtain highly-ordered cylindrical domains. The polymer blocks are cleaved by means of a mild UV exposure and then the pore material is washed out of the polymer film by ultra-pure water resulting in arrays of nanoporous thin films to remove one block. The removal of the PEO materials from the pores was proven using the grazing-incidence small-angle X-ray scattering (GISAXS) technique. The treatment of the polymer film during the washing process was observed in real time after two different UV exposure time (1 and 4 h) in order to draw conclusions regarding the dynamics of the removal process. In-situ X-ray reflectivity measurements provide statistically significant information about the change in the layer thickness as well as the roughness and electron density of the polymer film during pore formation. 4 H UV exposure was found to be more efficient for PEO cleavage. By in-situ SFM measurements, the structure of the ultra-thin block copolymer films was also analysed and, thus, the kinetics of the washing process was elaborated. The results from both measurements confirmed that the washing procedure induces irreversible change in morphology to the surface of the thin film.
Water Absorption and Hygrothermal Aging Behavior of Wood-Polypropylene Composites
Authors: Wang Wei , Guo Xiaomin , Zhao Defang , Liu Liu , Zhang Ruiyun , Yu Jianyong
Published: April 2020

Environmentally sound composites reinforced with natural fibers or particles interest many researchers and engineers due to their great potential to substitute the traditional composites reinforced with glass fibers. However, the sensitivity of natural fiber-reinforced composites to water has limited their applications. In this paper, wood powder-reinforced polypropylene composites (WPCs) with various wood content were prepared and subjected to water absorption tests to study the water absorption procedure and the effect of water absorbed in the specimens on the mechanical properties. Water soaking tests were carried out by immersion of composite specimens in a container of distilled water maintained at three different temperatures, 23, 60 and 80 °C. The results showed that the moisture absorption content was related to wood powder percentage and they had a positive relationship. The transfer process of water molecules in the sample was found to follow the Fickian model and the diffusion constant increased with elevated water temperature. In addition, tensile and bending tests of both dry and wet composite samples were conducted and the results indicated that water absorbed in composite specimens degraded their mechanical properties. The tensile strength and modulus of the composites reinforced with 15, 30, 45 wt % wood powder decreased by 5.79%, 17.2%, 32.06% and 25.31%, 33.6%, 47.3% respectively, compared with their corresponding dry specimens. The flexural strength and modulus of the composite samples exhibited a similar result. Furthermore, dynamic mechanical analysis (DMA) also confirmed that the detrimental effect of water molecules on the composite specimens.
Cartilage Tissue-Mimetic Pellets with Multifunctional Magnetic Hyaluronic Acid-Graft-Amphiphilic Gelatin Microcapsules for Chondrogenic Stimulation
Authors: Hou Kai-Ting , Liu Ting-Yu , Chiang Min-Yu , Chen Chun-Yu , Chang Shwu-Jen , Chen San-Yuan
Published: April 2020

Articular cartilage defect is a common disorder caused by sustained mechanical stress. Owing to its nature of avascular, cartilage had less reconstruction ability so there is always a need for other repair strategies. In this study, we proposed tissue-mimetic pellets composed of chondrocytes and hyaluronic acid-graft-amphiphilic gelatin microcapsules (HA-AGMCs) to serve as biomimetic chondrocyte extracellular matrix (ECM) environments. The multifunctional HA-AGMC with specific targeting on CD44 receptors provides excellent structural stability and demonstrates high cell viability even in the center of pellets after 14 days culture. Furthermore, with superparamagnetic iron oxide nanoparticles (SPIOs) in the microcapsule shell of HA-AGMCs, it not only showed sound cell guiding ability but also induced two physical stimulations of static magnetic field(S) and magnet-derived shear stress (MF) on chondrogenic regeneration. Cartilage tissue-specific gene expressions of Col II and SOX9 were upregulated in the present of HA-AGMC in the early stage, and HA-AGMC+MF+S held the highest chondrogenic commitments throughout the study. Additionally, cartilage tissue-mimetic pellets with magnetic stimulation can stimulate chondrogenesis and sGAG synthesis.
Exploring Needle-Like Zinc Oxide Nanostructures for Improving Dental Resin Sealers: Design and Evaluation of Antibacterial, Physical and Chemical Properties
Authors: Collares Fabrício M , Garcia Isadora M , Klein Mariana , Parolo Clarissa F , Sánchez Felipe Antonio L , Takimi Antônio , Bergmann Carlos P , Samuel Susana Maria W , Melo Mary Anne , Leitune Vicente CB
Published: April 2020

This study aimed to evaluate the effect of needle-like zinc oxide nanostructures (ZnO-NN) on the physical, chemical, and antibacterial properties of experimental methacrylate-based dental sealers. ZnO-NN was synthesized and characterized. ZnO-NN was added to a co-monomer blend at 20, 30, and 40 wt.%. One group without ZnO-NN was used as a control. The dental resin sealers were evaluated for their flow, film thickness, water sorption, solubility, radiopacity, degree of conversion (DC), dental-sealer interface characterization via micro-Raman, and antibacterial activity. ZnO-NN presented a mean needle diameter of 40 nm and 16 m2/g of surface area. There was no difference among groups containing ZnO-NN regarding their flow. The ZnO-NN addition significantly increased the film thickness. Water sorption and solubility tests showed no difference among groups. The radiopacity increased, and DC decreased with higher concentrations of ZnO-NN. Micro-Raman suggested that ZnO-NN was in close contact with root canal dentin. Overall, the incorporation of ZnO-NN provided an antibacterial effect against Enterococcus faecalis without a significant detrimental impact on the physical and chemical functionality of the material. The use of ZnO-NN as an inorganic filler is a potential application within dental materials intended for root canal treatment.
Melting Kinetics of Nascent Poly(tetrafluoroethylene) Powder
Authors: Christakopoulos Fotis , Troisi Enrico , Tervoort Theo A.
Published: April 2020

The melting behavior of nascent poly(tetrafluoroethylene) (PTFE) was investigated by way of differential scanning calorimetry (DSC). It is well known that the melting temperature of nascent PTFE is about 344 ∘ C, but reduces to 327 ∘ C for once molten material. In this study, the melting temperature of nascent PTFE crystals was found to strongly depend on heating rate, decreasing considerably for slow heating rates. In addition, during isothermal experiments in the temperature range of 327 ∘ C < T < 344 ∘ C, delayed melting of PTFE was observed, with complete melting only occurring after up to several hours. The melting kinetics of nascent PTFE were analyzed by means of the isoconversional methodology, and an apparent activation energy of melting, dependent on the conversion, was determined. The compensation effect was utilized in order to derive the pre-exponential factor of the kinetic model. The numerical reconstruction of the kinetic model was compared with literature models and an Avrami-Erofeev model was identified as best fit of the experimental data. The predictions of the kinetic model were in good agreement with the observed time-dependent melting of nascent PTFE during isothermal and constant heating-rate experiments.
Polymer Biointerfaces
Authors: Lehocký Marián , Humpolíček Petr
Published: April 2020

Polymer biointerfaces are considered suitable materials for the improvement and development of numerous applications [...]
Nano-Indentation Response of Ultrahigh Molecular Weight Polyethylene (UHMWPE): A Detailed Analysis
Authors: Iqbal Tanveer , Camargo S. S. , Yasin Saima , Farooq Ujala , Shakeel Ahmad
Published: April 2020

Nano-indentation, a depth sensing technique, is a useful and exciting tool to investigate the surface mechanical properties of a wide range of materials, particularly polymers. Knowledge of the influence of experimental conditions employed during nano-indentation on the resultant nano-mechanical response is very important for the successful design of engineering components with appropriate surface properties. In this work, nano-indentation experiments were carried out by selecting various values of frequency, amplitude, contact depth, strain rate, holding time, and peak load. The results showed a significant effect of amplitude, frequency, and strain rate on the hardness and modulus of the considered polymer, ultrahigh molecular weight polyethylene (UHMWPE). Load-displacement curves showed a shift towards the lower indentation depths along with an increase in peak load by increasing the indentation amplitude or strain rate. The results also revealed the strong dependence of hardness and modulus on the holding time. The experimental data of creep depth as a function of holding time was successfully fitted with a logarithmic creep model (R2 ≥ 0.98). In order to remove the creeping effect and the nose problem, recommended holding times were proposed for the investigated polymer as a function of different applied loads.
Treatment of Secondary Dust Produced in Rotary Hearth Furnace through Alkali Leaching and Evaporation–Crystallization Processes
Authors: Liang Shuang , Liang Xiaoping , Tang Qian
Published: April 2020

This paper presents the results of an experimental study on the extraction of KCl and the improvement of the zinc grade of secondary dust obtained from rotary-hearth-furnace secondary dust (RHF secondary dust) using alkali leaching (Na2CO3 solution) and evaporation–crystallization processes. The effects of the liquid–solid ratio and Na2CO3 content on the element leaching ratio in the alkali leaching process, as well as the effects of the volume–evaporation ratio and cooling temperature on KCl extraction in the evaporation–crystallization process, were investigated. The results showed that the optimum liquid–solid ratio was 6:1, and the optimum quantity of Na2CO3 was 1.5 times the basic quantity. The recovery ratio of zinc reached 95.23%, and the leaching ratio of K reached 79.01%. The experimental results of the evaporation–crystallization process demonstrated that the evaporation temperature was 80 °C, the volume evaporation ratio was 50%, the cooling temperature was 25 °C, and the mass fraction of K2O in the obtained crystals was 58.99%.
Antioxidant Activity and Sensory Improvement of Angelica dahurica cv. Yubaizhi Essential Oil on Sunflower Oil during High-temperature Storage
Authors: Wang Dongying , Meng Yudong , Wang Chenxin , Wang Xuede , Blasi Francesca
Published: April 2020

The oxidative state of sunflower oil during high-temperature storage has been facing large challenges. In the study, the antioxidant effect of the essential oil of Angelica dahurica cv. Yubaizhi (ADEO) in sunflower oil was explored. In the high-temperature storage for 24 days at 65 °C, ADEO (800 ppm) was able to markedly inhibit the development of the acid value (AV), peroxide value (PV), p-anisidine value (AnV), total oxidation value (TOTOX), thiobarbituric acid reactive substances (TBARS), total polar compounds (TPC), and the absorbance at 232 and 268 nm (p < 0.01 or p < 0.05) of sunflower oil and to prominently inhibit the transformation between unsaturated fatty acids (UFA) and saturated fatty acids (SFA). Interestingly, the synergistic effect of ADEO (400 ppm) and tert-butyl hydroquinone (TBHQ, 100 ppm) was demonstrated. Furthermore, the sensory attributes such as flavor, taste, and overall acceptability of oxidized sunflower oil added by ADEO at 200, 400, and 800 ppm were memorably elevated (p < 0.05). Besides, one of its main compounds, myrcene, was demonstrated to be its active compound during the whole investigation. Consequently, TBHQ at 200 ppm could be substituted by ADEO at 800 ppm and myrcene at 69.8 ppm in the high-temperature storage at 65 °C of sunflower oil.
Temperature Distribution Estimation in a Dwight–Lloyd Sinter Machine Based on the Combustion Rate of Charcoal Quasi-Particles
Authors: Wang Ziming , Ohno Ko-ichiro , Nonaka Shunsuke , Maeda Takayuki , Kunitomo Kazuya
Published: April 2020

The coke combustion rate in an iron ore sintering process is one of the most important determining factors of quality and productivity. Biomass carbon material is considered to be a coke substitute with a lower CO2 emission in the sintering process. The purpose of this study was to investigate the combustion rate of a biomass carbon material and to use a sintering simulation model to calculate its temperature profile. The samples were prepared using alumina powder and woody biomass powder. To simplify the experimental conditions, alumina powder, which cannot be reduced, was prepared as a substitute of iron ore. Combustion experiments were carried out in the open at 1073 K~1523 K. The results show that the combustion rates of the biomass carbon material were higher than that of coke. The results were analyzed using an unreacted core model with one reaction interface. The kinetic analysis found that the kc of charcoal was higher than that of coke. It is believed that the larger surface area of charcoal may affect its combustion rate. The analysis of the sintering simulation results shows that the high temperature range of charcoal was smaller than that of coke because of charcoal’s low fixed carbon content and density.
Integrated Method of Monitoring and Optimization of Steam Methane Reformer Process
Authors: Zečević Nenad , Bolf Nenad
Published: April 2020

Reforming of natural gas with steam represents the most energy-intensive part of ammonia production. An integrated numerical model for calculating composition of primary reforming products with cross-checking of outlet methane molar concentration, heat duty, maximum tube wall temperature, tube pressure drops, and approach to equilibrium was set up involving production parameters. In particular, the model was used for continuous monitoring and optimization of a steam methane reformer (SMR) catalyst in ammonia production. The calculations involve the solution of material and energy balance equations along with reaction kinetic expressions. Open source code based on Matlab file was used for modelling and calculation of various physical properties of the reacting gases. One of the main contributions is development of the rapid integrated method for data exchange between any distributed control system (DCS) and the model to accomplish continuous monitoring and optimization of SMR catalyst and reformer tubes. Integrated memory block was proposed for rapid synchronization between commercial DCS with the model solver. The developed model was verified with the industrial top-fired SMR unit in ammonia production located in Petrokemija, Croatia. Practical application of proposed solution can ensure overall energy savings of up to 3% in ammonia production.
Understanding the Operating Mode of Fe0/Fe-Sulfide/H2O Systems for Water Treatment
Authors: Xiao Minhui , Hu Rui , Cui Xuesong , Gwenzi Willis , Noubactep Chicgoua
Published: April 2020

The general suitability of water treatment systems involving metallic iron (Fe0) is well-established. Various attempts have been made to improve the efficiency of conventional Fe0 systems. One promising approach combines granular Fe0 and an iron sulfide mineral to form Fe0/Fe-sulfide/H2O systems. An improved understanding of the fundamental principles by which such systems operate is still needed. Through a systematic analysis of possible reactions and the probability of their occurrence, this study establishes that sulfide minerals primarily sustain iron corrosion by lowering the pH of the system. Thus, chemical reduction mediated by FeII species (indirect reduction) is a plausible explanation for the documented reductive transformations. Such a mechanism is consistent with the nature and distribution of reported reaction products. While considering the mass balance of iron, it appears that lowering the pH value increases Fe0 dissolution, and thus subsequent precipitation of hydroxides. This precipitation reaction is coupled with the occlusion of contaminants (co-precipitation or irreversible adsorption). The extent to which individual sulfides impact the efficiency of the tested systems depends on their intrinsic reactivities and the operational conditions (e.g., sulfide dosage, particle size, experimental duration). Future research directions, including the extension of Fe0/Fe-sulfide/H2O systems to drinking water filters and (domestic) wastewater treatment using the multi-soil-layering method are highlighted.
Approximate Moment Methods for Population Balance Equations in Particulate and Bioengineering Processes
Authors: Dürr Robert , Bück Andreas
Published: April 2020

Population balance modeling is an established framework to describe the dynamics of particle populations in disperse phase systems found in a broad field of industrial, civil, and medical applications. The resulting population balance equations account for the dynamics of the number density distribution functions and represent (systems of) partial differential equations which require sophisticated numerical solution techniques due to the general lack of analytical solutions. A specific class of solution algorithms, so-called moment methods, is based on the reduction of complex models to a set of ordinary differential equations characterizing dynamics of integral quantities of the number density distribution function. However, in general, a closed set of moment equations is not found and one has to rely on approximate closure methods. In this contribution, a concise overview of the most prominent approximate moment methods is given.
Three Commonly Utilized Scholarly Databases and a Social Network Site Provide Different, But Related, Metrics of Pharmacy Faculty Publication
Authors: Burghardt Kyle J. , Howlett Bradley H. , Khoury Audrey S. , Fern Stephanie M. , Burghardt Paul R.
Published: April 2020

Scholarly productivity is a critical component of pharmacy faculty effort and is used for promotion and tenure decisions. Several databases are available to measure scholarly productivity; however, comparisons amongst these databases are lacking for pharmacy faculty. The objective of this work was to compare scholarly metrics from three commonly utilized databases and a social networking site focused on data from research-intensive colleges of pharmacy and to identify factors associated with database differences. Scholarly metrics were obtained from Scopus, Web of Science, Google Scholar, and ResearchGate for faculty from research-intensive (Carnegie Rated R1, R2, or special focus) United States pharmacy schools with at least two million USD in funding from the National Institutes of Health. Metrics were compared and correlations were performed. Regression analyses were utilized to identify factors associated with database differences. Significant differences in scholarly metric values were observed between databases despite the high correlations, suggestive of systematic variation in database reporting. Time since first publication was the most common factor that was associated with database differences. Google Scholar tended to have higher metrics than all other databases, while Web of Science had lower metrics relative to other databases. Differences in reported metrics between databases are apparent, which may be attributable to the time since first publication and database coverage of pharmacy-specific journals. These differences should be considered by faculty, reviewers, and administrative staff when evaluating scholarly performance.
Diatoms in Paleoenvironmental Studies of Peatlands
Authors: Carballeira Rafael , Pontevedra-Pombal Xabier
Published: April 2020

The great diversity of diatoms in aquatic ecosystems and their close relationship with water chemistry make them one of the most informative and widely used biological proxies in paleoenvironmental studies of wetlands, except for peatland ecosystems. Currently, significant controversy still exists over the preservation of diatoms in peat. However, considerable evidence indicates that diatoms remain in good condition in minerotrophic peatlands, and they have been successfully used in paleoenvironmental studies in high-latitude regions and especially in Southern Europe.
Postsecular Plurality in the Middle East: Expanding the Postsecular Approach to a Power Politics of Becoming
Authors: Barbato Mariano
Published: April 2020

Embedded in a critically adapted version of Jürgen Habermas’ postsecular approach, this article analyzes empirically and evaluates normatively the role of religion in the Middle East. Integrating and adapting William Connolly’s understanding of political change as power politics of becoming, the argument is that an authoritarian pluralism is evolving that, in contrast to secular nationalism and Political Islam, can be called postsecular insofar as it attempts to integrate more strata of the population into the public discourse, regardless of their religious creed but based on interreligious plurality. The Document on Human Fraternity, signed 2019 in Abu Dhabi, is a prime example of that postsecular trend embedded in power politics. The article concludes that the turmoil of the Arab Spring did not pave the way for democracy but for authoritarian and partisan versions of a postsecular public that try to accommodate the plurality of the Middle East.
Classification of All Non-Isomorphic Regular and Cuspidal Arm Anatomies in an Orthogonal Metamorphic Manipulator
Authors: Koukos-Papagiannis Christos , Moulianitis Vassilis , Aspragathos Nikos
Published: April 2020

This paper proposes a classification of all non-isomorphic anatomies of an orthogonal metamorphic manipulator according to the topology of workspace considering cusps and nodes. Using symbolic algebra, a general kinematics polynomial equation is formulated, and the closed-form parametric solution of the inverse kinematics is obtained for the coming anatomies. The metamorphic design space was disjointed into eight distinct subspaces with the same number of cusps and nodes plotting the bifurcating and strict surfaces in a cartesian coordinate system { θ π 1 , θ π 2 , d 4 } . In addition, several non-singular, smooth and continuous trajectories are simulated to show the importance of this classification.