1,138 results on '"Processing and Performance"'
Search Results
1102. Chain-extended flexible polymers
- Author
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Lemstra, P.J., Bastiaansen, C.W.M., Meijer, H.E.H., and Processing and Performance
- Subjects
stomatognathic system ,macromolecular substances - Abstract
High‐strength/high‐modulus structures such as fibres, tapes and rods can be produced currently on the basis of intrinsically flexible macromolecules. The prime example amongst these new developments is gelspinning of high‐molecular‐weight polyethylene resulting in fibrous structures possessing tenacities of 3–4 GPa and corresponding moduli up to appr. 150 GPa. The basic aspects of chain‐extension for polyethylene will be discussed in relation to the various routes toward oriented/extended PE structures as well as recent developments concerning the utilization of other flexible polymeric systems for the production of high‐strength/high‐modulus fibres.
- Published
- 1986
1103. Hydrogen storage in sonicated carbon materials
- Author
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Miroslav Haluska, Urszula Dettlaff-Weglikowska, Y.-M Choi, M. Becher, M. Hulman, P. Bernier, A. Quintel, I Stepanek, P. Downes, Georg S. Duesberg, S. Roth, Michael Hirscher, and Processing and Performance
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Materials science ,Hydrogen ,Cryo-adsorption ,Thermal desorption spectroscopy ,Sonication ,chemistry.chemical_element ,Nanotechnology ,General Chemistry ,Carbon nanotube ,law.invention ,Hydrogen storage ,chemistry ,Chemical engineering ,law ,General Materials Science ,Graphite ,Carbon - Abstract
The hydrogen storage in purified single-wall carbon nanotubes (SWNTs), graphite and diamond powder was investigated at room temperature and ambient pressure. The samples were sonicated in 5 M HNO3 for various periods of time using an ultrasonic probe of the alloy Ti-6Al-4V. The goal of this treatment was to open the carbon nanotubes. The maximum value of overall hydrogen storage was found to be 1.5 wt %, as determined by thermal desorption spectroscopy. The storage capacity increases with sonication time. The sonication treatment introduces particles of the Ti alloy into the samples, as shown by X-ray diffraction, transmission electron microscopy, and chemical analysis. All of the hydrogen uptake can be explained by the assumption that the hydrogen is only stored in the Ti-alloy particles. The presence of Ti-alloy particles does not allow the determination of whether a small amount of hydrogen possibly is stored in the SWNTs themselves, and the fraction of nanotubes opened by the sonication treatment is unknown.
1104. Chiral polyesters by dynamic kinetic resolution polymerization
- Author
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Hilker, I., Verzijl, G. K. M., Anja Palmans, Heise, A., Macromolecular and Organic Chemistry, Processing and Performance, and Macro-Organic Chemistry
- Abstract
No abstract.
1105. Chaotic advection induced by a magnetic chain in a rotating magnetic field
- Author
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Kang, T. G., Hulsen, M. A., Patrick Anderson, Den Toonder, J. M. J., Meijer, H. E. H., Processing and Performance, Microsystems, Group Den Toonder, and Institute for Complex Molecular Systems
- Subjects
Maxwell stress tensor ,Magnetic chain ,Fictitious domain method ,Rotating magnetic field ,Haotic advection - Abstract
We investigated chaotic advection induced by a magnetic chain in a two-dimensional circular cavity under the influence of a rotating magnetic field. Our focus is on the dynamics of the chain and the route to induce chaotic mixing. A direct simulation method based on the Maxwell stress tensor and a fictitious domain method is employed to solve magnetic and flow problems in a coupled manner. The motion of the chain is significantly affected by the Mason number, the ratio of viscous force to magnetic force. At a lower Mason number, the chain rotates like a rigid body following the field. Alternating break-up and reformation of the chain are observed within a limited range of the Mason number, which induce two typical flows: a single rotating flow and two co-rotating flows. From a series of deformation patterns of a blob, we found that the two alternating flows result in enhanced mixing, showing an exponential increase of the interfacial length.
1106. A 3D numerical method for fluid-structure interaction in heart valves
- Author
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Loon, R., Rutten, M. C. M., Patrick Anderson, Vosse, F. N., Biomedical Engineering, Cardiovascular Biomechanics, and Processing and Performance
1107. Aggregation, fracture initiation, and strength of PP/CaCO3 composites
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Béla Pukánszky, GM Kim, S. Molnár, Goerg H. Michler, Erika Fekete, and Processing and Performance
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Extrusion moulding ,Polypropylene ,Materials science ,Polymers and Plastics ,General Chemistry ,Condensed Matter Physics ,Critical value ,chemistry.chemical_compound ,Flexural strength ,chemistry ,Ultimate tensile strength ,Materials Chemistry ,Particle ,Extrusion ,Particle size ,Composite material - Abstract
Polypropylene/CaC03 composites were homogenized in a twin-screw compounder and then injection molded into tensile bars. Six different fillers were used in a wide range of average particle sizes between 0.08 and 12 pm. Tensile and flexural properties were measured by standard techniques, while impact resistance was determined by instrumented impact testing. Structure was characterized by light and electron microscopy, while failure initiation and propagation was studied with in situ high-voltage electron microscopy. The results showed that aggregation of particulate fillers occurs when their particle size is smaller than a critical value. This critical size depends on component properties and processing conditions. Strength and impact resistance usually decrease with increasing number of aggregates. The presence of aggregation can be detected by the use of a simple semiempirical model. Comparison of samples prepared by two different technologies showed that twin-screw extrusion and injection molding leads to relatively homogeneous composites, which was indicated by smaller deviations of the properties from theoretical predictions. In spite of the accept-able dispersion, impact resistance showed a large standard deviation, probably determined by the local variation of structure. In composites containing relatively large particles, the dominating micromechanical deformation process is debonding, while in the presence of extensive aggregation of small particles, cracks are initiated inside and propagate through aggregates. Mixed-mode failure may also occur at certain intermediate particle sizes.
1108. Bio-inspired microfluidic pumping by roll-printed artificial cilia
- Author
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Ye Wang, Zhang, S., Ruth Cardinaels, Patrick Anderson, Jaap den Toonder, Microsystems, Electro-Optical Communication, Processing and Performance, Group Den Toonder, and Institute for Complex Molecular Systems
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Roll-pulling process ,Cleanroom-free fabrication ,Cilia ,Microfluidic pumping - Abstract
Magnetic artificial cilia are bio-inspired micro-hairs covering a surface that can be actuated using a magnetic field to pump or mix fluids in microfluidic devices. This paper presents a novel fabrication method to realize magnetic artificial cilia using a roll-printing process. When integrated in a closedloop channel, the artificial cilia were shown to be capable of generating substantial microfluidic pumping using external magnetic actuation. The development of this cleanroom-free, high speed and potentially large area method of production of artificial cilia is another step towards their implementation in real-life applications.
1109. MEMS tunable capacitors and switches for RF applications
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H.A.C. Tilmans, P. van Eerd, Theodoor G Rijks, Robert Puers, J.M.J. den Toonder, A. Jourdain, J. De Coster, A. van Dijken, J.T.M. van Beek, J.M. Scheer, J.W. Weekamp, Peter G. Steeneken, M.J.E. Ulenaers, Processing and Performance, Microsystems, Group Den Toonder, and Institute for Complex Molecular Systems
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Microelectromechanical systems ,Materials science ,business.industry ,Capacitive sensing ,Electrical engineering ,Hardware_PERFORMANCEANDRELIABILITY ,Filter capacitor ,Inductor ,Die (integrated circuit) ,law.invention ,Capacitor ,law ,Hardware_GENERAL ,Q factor ,Hardware_INTEGRATEDCIRCUITS ,Insertion loss ,business - Abstract
RF MEMS capacitive switches and tunable capacitors have been realized in an industrialized thin-film process developed for manufacturing high-quality inductors and capacitors. Combining integrated passives with high-performance tuning and switching elements on the same die offers a potential for building a new generation of RF front-ends for hand-held mobile communication. Capacitive switches with an insertion loss of 0.4 dB and an isolation of 17 dB at 1 GHz have been demonstrated. Dual-gap relay type tunable capacitors have been fabricated that show a continuous and reversible tuning ratio of 12 together with a quality factor larger than 150 at frequencies higher than 0.5 GHz. These are the highest tuning ratio and quality factor reported to date. A 0-level packaging concept that is compatible with the fabrication technology has been adopted.
1110. Predicting the long-term failure of polycarbonate: A constitutive approach
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Klompen, E. T. J., Tom Engels, Janssen, R. P. M., Govaert, L. E., Meijer, H. E. H., Mechanical Engineering, and Processing and Performance
- Abstract
In this study, an in-house numerical model is employed to predict the time-to-failure of polycarbonate under long-term constant or cyclic loading. This elasto-viscoplastic model captures the intrinsic deformation behavior of the glassy polymer. The model parameters are determined from uni-axial compression testing. In the case of long-term loading, however, special attention should be given to the intrinsic deformation behavior, as this might change within the time-scale of the experiment. Therefore, an elaborate investigation is performed to implement so-called aging kinetics in this model. It is shown that the application of approach leads to accurate predictions of time-to-failure under both constant loading and cyclic loading conditions. Moreover, the current model is based on a single parameter set and is molecular weight independent.
1111. Arrested fluid-fluid phase separation in depletion systems: Implications of the characteristic length on gel formation and rheology
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Hans M. Wyss, Suliana Manley, Kunimasa Miyazaki, David A. Weitz, David R. Reichman, V. Trappe, Andrew B. Schofield, Laura J. Kaufman, Jacinta C. Conrad, Processing and Performance, and Group Wyss
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Materials science ,Characteristic length ,Spinodal decomposition ,Mechanical Engineering ,Thermodynamics ,Modulus ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Shear modulus ,Condensed Matter::Soft Condensed Matter ,Colloid ,Rheology ,Dynamic light scattering ,Mechanics of Materials ,0103 physical sciences ,Volume fraction ,General Materials Science ,010306 general physics ,0210 nano-technology - Abstract
We investigate the structural, dynamical, and rheological properties of colloid-polymer mixtures in a volume fraction range of φ=0.15-0.35. Our systems are density-matched, residual charges are screened, and the polymer-colloid size ratio is ∼0.37. For these systems, the transition to kinetically arrested states, including disconnected clusters and gels, coincides with the fluid-fluid phase separation boundary. Structural investigations reveal that the characteristic length, L, of the networks is a strong function of the quench depth: for shallow quenches, L is significantly larger than that obtained for deep quenches. By contrast, L is for a given quench depth almost independent of φ; this indicates that the strand thickness increases with φ. The strand thickness determines the linear rheology: the final relaxation time exhibits a strong dependence on φ, whereas the high frequency modulus does not. We present a simple model based on estimates of the strand breaking time and shear modulus that semiquantitatively describes the observed behavior. © 2010 The Society of Rheology.
1112. Cell-based schedule dependent drug combination screening with a droplet-based microfluidic system
- Author
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Guansheng Du, Den Toonder, J. M. J., Fang, Q., Processing and Performance, Microsystems, Group Den Toonder, and Institute for Complex Molecular Systems
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Microfluidic droplet ,High-throughput ,Cell ,Drug combination - Abstract
We proposed an integrated and robust microfluidic platform to perform cell-based schedule dependent drug combination screening. Multiple manipulations of cells in droplets, including cell dispensing, culture, drug stimulation and viability test were performed based on a 2D microfluidic droplet array. The screening of flavopiridol (Fla) and 5-fluorouracil (5Flu) in different sequence was carried out in 342 addressable droplets, with a consumption of ∼3 μg drug for each experiment.
1113. Chaotic mixing in microfluidic devices
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Singh, M. K., Patrick Anderson, Meijer, H. E. H., Processing and Performance, and Mechanical Engineering
1114. Output error Hamiltonian neural networks (OE-HNN)
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Sarvin Moradi, Nick Jaensson, Roland Toth, Maarten Schoukens, Control Systems, Machine Learning for Modelling and Control, Electrical Engineering, EAISI, ICMS Affiliated, Processing and Performance, EAISI High Tech Systems, Autonomous Motion Control Lab, Control of high-precision mechatronic systems, Cyber-Physical Systems Center Eindhoven, and Dynamic Networks: Data-Driven Modeling and Control
1115. Fibre-reinforced composites with tailored interphases using PPE/epoxy blends as a matrix system
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Heh Han Meijer, RW Rob Venderbosch, P.L. Lemstra, Ton Peijs, and Processing and Performance
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chemistry.chemical_classification ,Materials science ,Composite number ,Ether ,Polymer ,Epoxy ,Solvent ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,visual_art ,Phase (matter) ,Ceramics and Composites ,visual_art.visual_art_medium ,Interphase ,Composite material ,Curing (chemistry) - Abstract
In this study poly(2,6-dimethyl-1,4-phenylene ether) (PPE) is introduced as a ductile thermoplastic matrix for high-performance carbon fibre-reinforced composites by using epoxy resin as a reactive solvent. An interesting feature of this reactive composite processing route is that the epoxy resin acts not only as an effective solvent, lowering the viscosity and processing temperature of the polymer matrix, but also provides an essential structural part of the final composite material. Upon curing and subsequent phase separation, a morphology of epoxy-coated fibres in a nearly pure PPE matrix results. This phenomenon is not only of great importance with respect to the possibility to drastically improve the adhesion between the fibres and the thermoplastic matrix, but also creates the challenge to tailor the mechanical properties of these in situ formed interlayers by changing the chemistry of the epoxy phase.
1116. Learning Constitutive Laws in Engineering Systems
- Author
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Sarvin Moradi, Nick Jaensson, Roland Toth, Maarten Schoukens, Control Systems, Machine Learning for Modelling and Control, Electrical Engineering, EAISI, ICMS Affiliated, Processing and Performance, EAISI High Tech Systems, Autonomous Motion Control Lab, Control of high-precision mechatronic systems, Cyber-Physical Systems Center Eindhoven, and Dynamic Networks: Data-Driven Modeling and Control
1117. Chaotic mixing induced by a magnetic chain in a rotating magnetic field
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Jmj Jaap den Toonder, Heh Han Meijer, Patrick D. Anderson, Tae Gon Kang, MA Martien Hulsen, Processing and Performance, Mechanical Engineering, Microsystems, Group Den Toonder, and Institute for Complex Molecular Systems
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Physics ,Rotating magnetic field ,ComputingMilieux_LEGALASPECTSOFCOMPUTING ,Lyapunov exponent ,Maxwell stress tensor ,Mechanics ,Breakup ,Magnetic field ,symbols.namesake ,Chaotic mixing ,Classical mechanics ,symbols ,Magnetic nanoparticles ,Mixing (physics) - Abstract
Chaotic mixing, induced by breakup and reformation of a magnetic chain under the influence of a rotating magnetic field, is studied. A direct simulation method combining the Maxwell stress tensor and a fictitious domain method is employed to solve flows with suspended magnetic particles. The motion of the chain is significantly dependent on the Mason number (Ma), the ratio of viscous force to magnetic force. The degree of chaos is characterized by the maximum Lyapunov exponents. We also track the interface of two fluids in time and calculate the rate of stretching as it is affected by the Mason number. The progress of mixing is visualized via a tracer particle-tracking method and is characterized by the discrete intensity of segregation. Within a limited range of Mason number, a magnetic chain rotates and breaks into smaller chains, and the detached chains connect again to form a single chain. The repeating topological changes of the chain lead to the most efficient way of chaotic mixing by stretching at chain breakup and folding due to rotational flows.
1118. Viscoelastic effects in multilayer polymer extrusion
- Author
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Patrick Anderson, Dooley, J., Meijer, H. E. H., Processing and Performance, and Mechanical Engineering
- Abstract
The effect of viscoelasticity on multilayer polymer extrusion is discussed. In these coextrusion processes predeterminedpatterns are created with a remarkable breadth of complexity even in geometrically simple dies viaelastic rearrangements caused by the second-normal stress differences. A computational method is offered,based on the mapping method, which quantitatively describes the flow-induced patterns. Besides that theresults are esthetically beautiful, they are also relevant for practice, since process and die design optimizationis now possible. Not only to minimize interface distortion, but potentially also to deliberately create new processesand products based on this flow-induced patterning of polymers.
1119. Analysis of mixing in three-dimensional time-periodic cavity flows
- Author
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Patrick D. Anderson, F.N. van de Vosse, O.S. Galaktionov, Heh Han Meijer, Gerrit W. M. Peters, Processing and Performance, and Cardiovascular Biomechanics
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Physics ,Mechanical Engineering ,Process (computing) ,Mechanics ,Condensed Matter Physics ,Tracking (particle physics) ,Displacement (vector) ,Quality (physics) ,Classical mechanics ,Mechanics of Materials ,Line (geometry) ,Vector field ,Boundary value problem ,Mixing (physics) - Abstract
A method to locate periodic structures in general three-dimensional Stokes flows with time-periodic boundary conditions is presented and applied to mixing cavity flows. Numerically obtained velocity fields and particle tracking schemes are used to provide displacement and stretching fields. From these the location and identification of periodic points can be derived. The presence or absence of these periodic points allows a judgement on the quality of the mixing process. The technique is general and efficient, and applicable to mixing flows for which no analytical velocity field is available (the case for all three-dimensional flows considered in this paper). Results are presented for three different mixing protocols in a three-dimensional time-periodic cavity flow, serving as an accessible test case for the methods developed. A major result is that periodic lines are obtained for these three-dimensional flows. These lines can be complex in geometry and their nature can change along a line from hyperbolic to elliptic. They can serve as practical criteria in the optimization of three-dimensional mixing processes.
1120. Nature-inspired active mixing in a microchannel
- Author
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Khatavkar, V. V., Patrick Anderson, Meijer, H. E. H., Jaap den Toonder, Processing and Performance, and Mechanical Engineering
- Subjects
ComputingMilieux_LEGALASPECTSOFCOMPUTING
1121. An in situ SAXS/WAXS/Raman spectroscopy study on the phase behavior of syndiotactic polystyrene (sPS)/solvent systems: Compound formation and solvent (dis)ordering
- Author
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Sanjay Rastogi, Jgp Han Goossens, PJ Piet Lemstra, and Processing and Performance
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Materials science ,Polymers and Plastics ,Small-angle X-ray scattering ,Organic Chemistry ,Methacrylate ,Inorganic Chemistry ,Solvent ,chemistry.chemical_compound ,Crystallography ,symbols.namesake ,Decalin ,chemistry ,Tacticity ,Phase (matter) ,Polymer chemistry ,Materials Chemistry ,symbols ,Polystyrene ,Raman spectroscopy - Abstract
In situ small- and wide-angle X-ray scattering (SAXS and WAXS) experiments combined with Raman spectroscopy and thermal analysis have been performed to study the phase behavior of syndiotactic polystyrene (sPS) solutions. Three different solvents were used, respectively, decalin, benzyl methacrylate, and cyclohexyl methacrylate. When sPS solutions are quenched, gel formation occurs. In these gels sPS adopts a helical conformation that is stabilized by the solvent molecules; in fact, compound formation occurs. From the combined experimental data it was concluded that two different structural modifications exist within the solvent-included helical -phase, respectively the -phase, in which the solvent molecules are intercalated and ordered between the phenyl rings of sPS, and a -phase, where the solvent ordering is lost. The so-called -phase, the solvent-free helical phase, was not observed in our studies. The transformation from the helical () phase to the planar zigzag () phase occurs via melting and recry...
1122. Thermodynamics of viscoelastic fluids: The temperature equation
- Author
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Peter Wapperom, MA Martien Hulsen, and Processing and Performance
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Materials science ,Mechanical Engineering ,Thermodynamics ,Non-equilibrium thermodynamics ,Dissipation ,Condensed Matter Physics ,Thermal conduction ,Heat capacity ,Non-Newtonian fluid ,Viscoelasticity ,Mechanics of Materials ,Compressibility ,General Materials Science ,Mechanical energy - Abstract
From the thermodynamics with internal variables we will derive the temperature equation for viscoelastic fluids. We consider the type of storage of mechanical energy, the dissipation of mechanical energy, the compressibility of the fluid, the nonequilibrium heat capacity and thermal expansion, and deformation induced anisotropy of the heat conduction. The well-known stress differential models that fit into the thermodynamic theory will be treated as an example. Adapting a power-law scaling of the shear moduli on temperature and density, as is usual in rubber elasticity, we will derive an approximation of the temperature equation in measurable quantities. This equation will be compared with experimental results.
1123. Space charge analysis of epoxy boron nanocomposites and the importance of dispersion techniques
- Author
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Peter Morshuis, Roman Kochetov, D. Saha, and Processing and Performance
- Subjects
010302 applied physics ,Materials science ,Nanocomposite ,nanocomposite ,020502 materials ,PEA ,02 engineering and technology ,pulsed electroacoustic technique ,01 natural sciences ,Space charge ,Homogeneous distribution ,epoxy ,Stress (mechanics) ,Boron nitride ,BN ,chemistry.chemical_compound ,0205 materials engineering ,chemistry ,0103 physical sciences ,Dispersion (optics) ,Particle ,Charge carrier ,space charge ,Composite material - Abstract
The present research work analyzes the space charge(S.C.) behavior and correlated dynamics in epoxy based nano-composites (NC) with hexagonal boron nitride (hBN) nano- particles.The importance of adopting an effective particle dispersion techniquefor producing such nano-composites is also experimentally validated.Three different dispersion techniques are contrasted in terms of thecorresponding space charge behavior exhibited, and the interplaybetween increasing filler content and dispersion techniques isinvestigated and reported. It is observed that an effective particledispersion technique results in a homogeneous distribution of nano-particles in the polymeric matrix, which in turn gives rise to evenlydistributed trap sites and affects the local mobility of charge carriers,effectively restraining them. More significantly, since most of thedeveloped trap-sites are located close to/in the interfacial zonebetween the injecting electrode and nano-composite specimen, aninitial, reasonably homogeneous distribution of nano-particles atrelatively lower loading (vol. %) is just as efficient in restricting bulkspace charge accumulation as higher loaded nano-compositespecimens – proving the importance of adopting an effective particledispersion technique. Achieving lower levels of bulk space chargeaccumulation (as demonstrated in this work) results in smallerinternal electric field distortion and stress in insulation material, thushaving the beneficial effect of prolonging operational life-time andincreased reliability.
1124. Environmental durability of flax fibres and their composites based on polypropylene matrix
- Author
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Stamboulis, A., Baillie, Ca, Garkhail, Sk, Melick, Hgh, Ton Peijs, and Processing and Performance
- Abstract
The environmental degradation behaviour of flax fibres and their polymer composites are explored. New upgraded Duralin flax fibres, which have been treated by a novel treatment process for improved moisture and rot sensitivity were studied. Environmental studies showed that these upgraded Duralin flax fibres absorb less moisture than untreated Green flax fibres, whereas the mechanical properties of the treated fibres were retained, if not improved. The effect of this novel flax fibre treatment on the environmental behaviour of natural-fibre-mat-reinforced thermoplastics (NMTs) is investigated by monitoring the moisture absorption and swelling, and measuring the residual mechanical properties of the flax/polypropylene composites at different moisture levels. The moisture absorption and swelling of the upgraded flax fibre composites is approximately 30% lower than that of composites based on Green flax fibres.
1125. Simulation of microfluidic fluid mixing using artificial cilia
- Author
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Baltussen, M. G. H. M., Jaap den Toonder, Bos, F. M., Patrick Anderson, and Processing and Performance
- Subjects
Micro-mixing ,Optical coherence tomography ,FEM simulation - Abstract
In previous work we developed a micro-mixer based on artificial cilia, that was experimentally proven to be very effective. Here, we present numerical simulations of the mixing process carried out using an advanced numerical tool, in combination with OCT experiments, that explain the observed effectiveness. As opposed to what was expected, fluid inertia was found to be the key ingredient for effective mixing.
1126. Contributions of the main flour constituents to dough rheology, and implications for dough quality and its assessment
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Meerts, M., Cardinaels, R., Oosterlinck, F., Christophe Courtin, Moldenaers, P., and Processing and Performance
1127. Passive transverse mechanical properties as a function of temperature of rat skeletal muscle in vitro
- Author
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Mark van Turnhout, Peters, G., Stekelenburg, A., Oomens, C., Soft Tissue Biomech. & Tissue Eng., and Processing and Performance
- Abstract
The objective of the current study was to determine the \textsl{in vitro} passive transverse mechanical properties of skeletal muscle with Dynamic Mechanical Thermal Analysis (DMTA) tests. The starting hypotheses was that the time-temperature-superposition principle could be used to expand the DMTA results to a 1 kHz frequency range. Experiments were performed with rat hind leg skeletal muscle tissue samples on a rotational rheometer using a parallel plate geometry. Because of the small size and low modulus of the samples, the standard test geometry was altered and the samples were shifted from the center to the edge of the plates. From strain sweep tests it became clear that for strains smaller than 0.003 the muscle tissue behaves linearly. In the linear region storage moduli ranged between 24 kPa (omega = 1 rad/s) and 42 kPa (omega = 100 rad/s) at T = 4 degrees C and 22 kPa and 33 kPa at 29 degrees C within the experimental frequency range. The loss modulus decreased with increasing frequency and ranged between 7 and 4 kPa at 4 degrees C and 4.5 and 3.5 kPa at 29 degrees C. Although the properties are clearly temperature dependent, a temperature shift in phase angle delta could not be detected, thus Time Temperature Superposition is not allowed for skeletal muscle in vitro.
1128. Polymeric actuating materials for microfluidic manipulation using external stimuli
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Wilderbeek, Hans T. A., Linden, Anthony J., Titie Mol, Judith De Goede, Wim Talen, Murray Gillies, Broer, Dirk J., Jaap den Toonder, and Processing and Performance
- Subjects
Computer Science::Robotics ,Micro-fluidics ,food and beverages ,Polymer chemistry & physics ,Polymer micro-actuators - Abstract
Responsive polymeric, micron-sized materials are described that can locally manipulate fluids by reversible micro-actuation. Selected examples of external stimuli, such as the use of a magnetic field are shown.
1129. Toughening Immiscible Polymer Blends: The Role of Interface-Crystallization-Induced Compatibilization Explored Through Nanoscale Visualization.
- Author
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Ahmadi H, van Heugten PMH, Veber A, Puskar L, Anderson PD, and Cardinaels R
- Abstract
This study explores the novel approach of interface-crystallization-induced compatibilization (ICIC) via stereocomplexation as a promising method to improve the interfacial strength in thermodynamically immiscible polymers. Herein, two distinct reactive interfacial compatibilizers, poly(styrene- co -glycidyl methacrylate)- graft -poly(l-lactic acid) (SAL) and poly(styrene- co -glycidyl methacrylate)- graft -poly(d-lactic acid) (SAD) are synthesized via reactive melt blending in an integrated grafting and blending process. This approach is demonstrated to enhance the interfacial strength of immiscible polyvinylidene fluoride/poly l-lactic acid (PVDF/PLLA) 50/50 blends via ICIC. IR nanoimaging indicates a cocontinuous morphology in the blends. The blend compatibilized with SAD exhibits a higher storage modulus, as unveiled by small amplitude oscillatory shear (SAOS) in the melt state at a temperature below the melting temperature of the stereocomplex (SC) crystals and by DMTA measurements in the solid state. This increase is attributed to the formation of a 200-300 nm thick rigid interfacial SC crystalline layer that is directly visible using AFM imaging and chemically characterized via IR nanospectroscopy. This ICIC also results in a significant toughening of the blend, with the elongation at break increasing more than 20-fold. Moreover, the fracture toughness factor obtained from single edge-notch bending (SENB) tests is doubled with ICIC as compared to the uncompatibilized blend, indicating the strong crack-resistance capability as a result of ICIC. This improvement is also evident in SEM images, where thinner and longer fibrillation is observed on the fractured surface in the presence of ICIC.
- Published
- 2024
- Full Text
- View/download PDF
1130. Molecularly Engineered Supramolecular Thermoresponsive Hydrogels with Tunable Mechanical and Dynamic Properties.
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Rijns L, Duijs H, Lafleur RPM, Cardinaels R, Palmans ARA, Dankers PYW, and Su L
- Subjects
- Biocompatible Materials chemistry, Animals, Mice, Benzamides, Hydrogels chemistry, Acrylic Resins chemistry, Temperature
- Abstract
Synthetic supramolecular polymers and hydrogels in water are emerging as promising biomaterials due to their modularity and intrinsic dynamics. Here, we introduce temperature sensitivity into the nonfunctionalized benzene-1,3,5-tricarboxamide ( BTA-EG
4 ) supramolecular system by incorporating a poly( N moiety, enabling 3D cell encapsulation applications. The viscous and structural properties in the solution state as well as the mechanical and dynamic features in the gel state of BTA-PNIPAM) mixtures were investigated and modulated. In the dilute state ( BTA-PNIPAM/BTA-EG4 mixtures were investigated and modulated. In the dilute state ( c ∼μM), BTA-PNIPAM acted as a chain capper below the cloud point temperature ( Tcp = 24 °C) but served as a cross-linker above T ratio was ∼100 times stiffer and ∼10 times less dynamic thancp . At higher concentrations ( c ∼mM), weak or stiff hydrogels were obtained, depending on the BTA-PNIPAM/BTA-EG4 ratio. The mixture with the highest BTA-PNIPAM ratio was ∼100 times stiffer and ∼10 times less dynamic than BTA-EG4 hydrogel. Facile cell encapsulation in 3D was realized by leveraging the temperature-sensitive sol-gel transition, opening opportunities for utilizing this hydrogel as an extracellular matrix mimic.- Published
- 2024
- Full Text
- View/download PDF
1131. Peptide Sequence Variations Govern Hydrogel Stiffness: Insights from a Multi-Scale Structural Analysis of H-FQFQFK-NH 2 Peptide Derivatives.
- Author
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De Maeseneer T, Cauwenbergh T, Gardiner J, White JF, Thielemans W, Martin C, Moldenaers P, Ballet S, and Cardinaels R
- Subjects
- Peptides chemistry, Amino Acid Sequence, Circular Dichroism, Protein Structure, Secondary, Spectroscopy, Fourier Transform Infrared, Hydrogels chemistry
- Abstract
Throughout the past decades, amphipathic peptide-based hydrogels have proven to be promising materials for biomedical applications. Amphipathic peptides are known to adopt β-sheet configurations that self-assemble into fibers that then interact to form a hydrogel network. A fundamental understanding of how the peptide sequence alters the structural properties of the hydrogels would allow for a more rational design of novel peptides for a variety of biomedical applications in the future. Therefore, the current work investigates how changing the type of amino acid, the amphipathic pattern, and the peptide length affects the secondary structure, fiber characteristics, and stiffness of peptide-based hydrogels. Hereto, seven amphipathic peptides of different sequence and length, four of which have not been previously reported, based on and including the hexapeptide H-Phe-Gln-Phe-Gln-Phe-Lys-NH
2 , are synthesized and thoroughly characterized by circular dichroism (CD), Fourier Transform Infrared (FTIR) spectroscopy, Wide Angle X-ray Scattering (WAXS), Small Angle X-ray Scattering (SAXS), Transmission Electron Microscopy (TEM), and Thioflavin T (ThT) fibrillization assays. The results show that a high amount of regularly spaced β-sheets, a high amount of fibers, and fiber bundling contribute to the stiffness of the hydrogel. Furthermore, a study of the time-dependent fibril formation process reveals complex transient dynamics. The peptide strands structure through an intermediate helical state prior to β-sheet formation, which is found to be concentration- and time-dependent., (© 2024 The Authors. Macromolecular Bioscience published by Wiley‐VCH GmbH.)- Published
- 2024
- Full Text
- View/download PDF
1132. Sticky Multicolor Mechanochromic Labels.
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de Castro LDC, Engels TAP, Oliveira ON Jr, and Schenning APHJ
- Abstract
Sticky-colored labels are an efficient way to communicate visual information. However, most labels are static. Here, we propose a new category of dynamic sticky labels that change structural colors when stretched. The sticky mechanochromic labels can be pasted on flexible surfaces such as fabric and rubber or even on brittle materials. To enhance their applicability, we demonstrate a simple method for imprinting structural color patterns that are either always visible or reversibly revealed or concealed upon mechanical deformation. The mechanochromic patterns are imprinted with a photomask during the ultraviolet (UV) cross-linking of acrylate-terminated cholesteric liquid crystal oligomers in a single step at room temperature. The photomask locally controls the cross-linking degree and volumetric response of the cholesteric liquid crystal elastomers (CLCEs). A nonuniform thickness change induced by the Poisson's ratio contrast between the pattern and the surrounding background might lead to a color-separation effect. Our sticky multicolor mechanochromic labels may be utilized in stress-strain sensing, building environments, smart clothing, security labels, and decoration.
- Published
- 2024
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1133. Powdered Cross-Linked Gelatin Methacryloyl as an Injectable Hydrogel for Adipose Tissue Engineering.
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De Maeseneer T, Van Damme L, Aktan MK, Braem A, Moldenaers P, Van Vlierberghe S, and Cardinaels R
- Abstract
The tissue engineering field is currently advancing towards minimally invasive procedures to reconstruct soft tissue defects. In this regard, injectable hydrogels are viewed as excellent scaffold candidates to support and promote the growth of encapsulated cells. Cross-linked gelatin methacryloyl (GelMA) gels have received substantial attention due to their extracellular matrix-mimicking properties. In particular, GelMA microgels were recently identified as interesting scaffold materials since the pores in between the microgel particles allow good cell movement and nutrient diffusion. The current work reports on a novel microgel preparation procedure in which a bulk GelMA hydrogel is ground into powder particles. These particles can be easily transformed into a microgel by swelling them in a suitable solvent. The rheological properties of the microgel are independent of the particle size and remain stable at body temperature, with only a minor reversible reduction in elastic modulus correlated to the unfolding of physical cross-links at elevated temperatures. Salts reduce the elastic modulus of the microgel network due to a deswelling of the particles, in addition to triple helix denaturation. The microgels are suited for clinical use, as proven by their excellent cytocompatibility. The latter is confirmed by the superior proliferation of encapsulated adipose tissue-derived stem cells in the microgel compared to the bulk hydrogel. Moreover, microgels made from the smallest particles are easily injected through a 20G needle, allowing a minimally invasive delivery. Hence, the current work reveals that powdered cross-linked GelMA is an excellent candidate to serve as an injectable hydrogel for adipose tissue engineering.
- Published
- 2024
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1134. RETRACTED: Liu et al. The Effect of Intrinsic Mechanical Properties on Reducing the Friction-Induced Ripples of Hard-Filler-Modified HDPE. Polymers 2023, 15 , 268.
- Author
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Liu C, Yuan C, and Liu S
- Abstract
The Polymers Editorial Office retracts the article "The Effect of Intrinsic Mechanical Properties on Reducing the Friction-Induced Ripples of Hard-Filler-Modified HDPE" [...].
- Published
- 2023
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1135. Phase behavior of medium-length hydrophobically associating PEO-PPO multiblock copolymers in aqueous media.
- Author
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Huysecom AS, Glorieux C, Thoen J, Thielemans W, Fustin CA, Moldenaers P, and Cardinaels R
- Abstract
Hypothesis: The micellization of block copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) is driven by the dehydration of PPO at elevated temperatures. At low concentrations, a viscous solution of isolated micelles is obtained, whereas at higher concentrations, crowding of micelles results in an elastic gel. Alternating PEO-PPO multiblock copolymers are expected to exhibit different phase behavior, with altered phase boundaries and thermodynamics, as compared to PEO-PPO-PEO triblock copolymers (Pluronics®) with equal hydrophobicity, thereby proving the pivotal role of copolymer architecture and molecular weight., Experiments: Multiple characterization techniques were used to map the phase behavior as a function of temperature and concentration of PEO-PPO multiblock copolymers (ExpertGel®) in aqueous solution. These techniques include shear rheology, differential and adiabatic scanning calorimetry, isothermal titration calorimetry and light transmittance. The micellar size and topology were studied by dynamic light scattering., Findings: Multiblocks have lower transition temperatures and higher thermodynamic driving forces for micellization as compared to triblocks due to the presence of more than one PPO block per chain. With increasing concentration, the multiblock copolymers in solution gradually evolve into a viscoelastic network formed by soluble bridges in between micellar nodes, whereas hairy triblock micelles jam into liquid crystalline phases resembling an elastic colloidal crystal., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)
- Published
- 2023
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1136. The Effect of Intrinsic Mechanical Properties on Reducing the Friction-Induced Ripples of Hard-Filler-Modified HDPE.
- Author
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Liu C, Yuan C, and Liu S
- Abstract
Ripple deformations induced by friction on polymeric materials have negative effects on the entire stability of operating machineries. These deformations are formed as a response to contacting mechanics, caused by the intrinsic mechanical properties. High-density polyethylene (HDPE) with varying silicon nitride (Si
3 N4 ) contents is used to investigate different ripple deformation responses by conducting single-asperity scratch tests. The relationship between the intrinsic mechanical properties and the ripple deformations caused by filler modifications is analyzed in this paper. The results show the coupling of the inherent mechanical properties, and the stick-slip motion of HDPE creates ripple deformations during scratching. The addition of the Si3 N4 filler changes the frictional response; the filler weakens the ripples and almost smoothens the scratch, particularly at 4 wt.%, but the continued increase in the Si3 N4 content produces noticeable ripples and fluctuations. These notable differences can be attributed to the yield and post-yield responses; the high yield stress and strain-hardening at 4 wt.% provide good friction resistance and stress distribution, thus a smooth scratch is observed. In contrast, increasing the filler content weakens both the yield and post-yield responses, leading to deformation. The results herein reveal the mechanism behind the initial ripple deformation, thus providing fundamental insights into universally derived friction-induced ripples.- Published
- 2023
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1137. Additive Manufacturing of Polyolefins.
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Christakopoulos F, van Heugten PMH, and Tervoort TA
- Abstract
Polyolefins are semi-crystalline thermoplastic polymers known for their good mechanical properties, low production cost, and chemical resistance. They are amongst the most commonly used plastics, and many polyolefin grades are regarded as engineering polymers. The two main additive manufacturing techniques that can be used to fabricate 3D-printed parts are fused filament fabrication and selective laser sintering. Polyolefins, like polypropylene and polyethylene, can, in principle, be processed with both these techniques. However, the semi-crystalline nature of polyolefins adds complexity to the use of additive manufacturing methods compared to amorphous polymers. First, the crystallization process results in severe shrinkage upon cooling, while the processing temperature and cooling rate affect the mechanical properties and mesoscopic structure of the fabricated parts. In addition, for ultra-high-molecular weight polyolefins, limited chain diffusion is a major obstacle to achieving proper adhesion between adjunct layers. Finally, polyolefins are typically apolar polymers, which reduces the adhesion of the 3D-printed part to the substrate. Notwithstanding these difficulties, it is clear that the successful processing of polyolefins via additive manufacturing techniques would enable the fabrication of high-end engineering products with enormous design flexibility. In addition, additive manufacturing could be utilized for the increased recycling of plastics. This manuscript reviews the work that has been conducted in developing experimental protocols for the additive manufacturing of polyolefins, presenting a comparison between the different approaches with a focus on the use of polyethylene and polypropylene grades. This review is concluded with an outlook for future research to overcome the current challenges that impede the addition of polyolefins to the standard palette of materials processed through additive manufacturing.
- Published
- 2022
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1138. Synergy of Fiber Surface Chemistry and Flow: Multi-Phase Transcrystallization in Fiber-Reinforced Thermoplastics.
- Author
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Looijmans SFSP, Spanjaards MMA, Puskar L, Cavallo D, Anderson PD, and van Breemen LCA
- Abstract
Fiber-reinforced polymer composites are largely employed for their improved strength with respect to unfilled matrices. Considering semi-crystalline materials under relevant processing conditions, the applied pressure and flow induce shear stresses at the fiber-polymer interface. These stresses may strongly enhance the nucleation ability of the fiber surface with respect to the quiescent case. It is thus possible to assume that the fiber features are no longer of importance and that crystallization is dominated by the effect of flow. However, by making use of an advanced experimental technique, i.e., polarization-modulated synchrotron infrared microspectroscopy (PM-SIRMS), we are able to show that the opposite is true for the industrially relevant case of isotactic polypropylene (iPP). With PM-SIRMS, the local chain orientation is measured with micron-size spatial resolution. This orientation can be related to the polymer nucleation density along the fiber surface. For various combinations of an iPP matrix and fiber, the degree of orientation in the cylindrical layer that develops during flow correlates well with the differences in nucleation density found in quiescent conditions. This result shows that the morphological development during processing of polymer composites is not solely determined by the flow field, nor by the nucleating ability of the fiber surface alone, but rather by a synergistic combination of the two. In addition, using finite element modeling, it is demonstrated that, under the experimentally applied flow conditions, the interphase structure formation is mostly dominated by the rheological characteristics of the material rather than perturbations in experimental conditions, such as shear rate, layer thickness, and temperature. This once again highlights the importance of matrix-filler interplay during flow and, thus, of material selection in the design of hybrid and lightweight composite technologies.
- Published
- 2022
- Full Text
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