scholarly journals Solvent Dependence of the Rheological Properties in Hydrogel Magnetorheological Plastomer

2020 ◽  
Vol 21 (5) ◽  
pp. 1793 ◽  
Author(s):  
Norhiwani Mohd Hapipi ◽  
Saiful Amri Mazlan ◽  
U. Ubaidillah ◽  
Siti Aishah Abdul Aziz ◽  
Muntaz Hana Ahmad Khairi ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Binary Mixtures ◽  
Binary Solvent ◽  
Iron Particles ◽  
Magnetic Performance ◽  
Solvent Dependence ◽  
Mr Effect ◽  
External Stimuli ◽  
Pva Hydrogel

Chemically crosslinked hydrogel magnetorheological (MR) plastomer (MRP) embedded with carbonyl iron particles (CIPs) exhibits excellent magnetic performance (MR effect) in the presence of external stimuli especially magnetic field. However, oxidation and desiccation in hydrogel MRP due to a large amount of water content as a dispersing phase would limit its usage for long-term applications, especially in industrial engineering. In this study, different solvents such as dimethyl sulfoxide (DMSO) are also used to prepare polyvinyl alcohol (PVA) hydrogel MRP. Thus, to understand the dynamic viscoelastic properties of hydrogel MRP, three different samples with different solvents: water, DMSO, and their binary mixtures (DMSO/water) were prepared and systematically carried out using the oscillatory shear. The outcomes demonstrate that the PVA hydrogel MRP prepared from precursor gel with water shows the highest MR effect of 15,544% among the PVA hydrogel MRPs. However, the samples exhibit less stability and tend to oxidise after a month. Meanwhile, the samples with binary mixtures (DMSO/water) show an acceptable MR effect of 11,024% with good stability and no CIPs oxidation. Otherwise, the sample with DMSO has the lowest MR effect of 7049% and less stable compared to the binary solvent samples. This confirms that the utilisation of DMSO as a new solvent affects the rheological properties and stability of the samples.

scholarly journals Material Characterization of Magnetorheological Elastomers with Corroded Carbonyl Iron Particles: Morphological Images and Field-dependent Viscoelastic Properties

2019 ◽  
Vol 20 (13) ◽  
pp. 3311 ◽  
Author(s):  
Siti Aishah Binti Abdul Aziz ◽  
Saiful Amri Mazlan ◽  
Nur Azmah Nordin ◽  
Nor Azlin Nazira Abd Rahman ◽  
U Ubaidillah ◽  
...  
Keyword(s):  
Carbonyl Iron ◽  
Matrix Material ◽  
Rheological Characteristics ◽  
Iron Particles ◽  
Ambient Conditions ◽  
X Ray ◽  
Field Dependent ◽  
Mr Effect

High temperatures and humidity could alter the field-dependent rheological properties of MR materials. These environmental phenomena may accelerate the deterioration processes that will affect the long-term rheological reliability of MR materials such as MR elastomer (MRE). This study therefore attempts to investigate the field-dependent rheological characteristics of MRE with corroded carbonyl iron particles (CIPs). The corroded CIPs were treated with hydrochloric acid (HCl) as a way of providing realistic environments in gauging the CIPs reaction towards the ambient conditions. The corroded CIPs along with silicone rubber as a matrix material were used in the fabrication of the MRE samples. To observe the effect of HCl treatment on the CIPs, the morphological observations of MREs with non-corroded and corroded CIPs were investigated via field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDX) and x-ray diffractometer (XRD). In addition, the magnetic properties were examined through the vibrating sample magnetometer (VSM), while the field-dependent rheological characteristics such as the storage modulus of MRE with the corroded CIPs were also tested and compared with the non-corroded CIPs. The results showed that the corroded CIPs possessed hydrangea-like structures. In the meantime, it was identified that a sudden reduction of up to 114% of the field-dependent MR effect of MRE with the corroded CIPs was observed as a result of the weakened interfacial bonding between the CIPs and the silicon in the outer layers of the CIPs structure.

Performance of Magnetorheological Elastomer Based Silicone/SAIB

2018 ◽  
Vol 772 ◽  
pp. 61-65
Author(s):  
Muntaz Hana Ahmad Khairi ◽  
Saiful Amri Mazlan ◽  
Ubaidillah ◽  
Siti Aishah Abdul Aziz ◽  
Norhiwani Mohd Hapipi
Keyword(s):  
Rheological Properties ◽  
Silicone Rubber ◽  
Carbonyl Iron ◽  
Excitation Frequency ◽  
Rubber Matrix ◽  
Iron Particles ◽  
Magnetorheological Elastomer ◽  
Magnetorheological Elastomers ◽  
Mr Effect ◽  
Strain Dependent

This study introduces a sucrose acetate isobutyrate (SAIB) as an additive of magnetorheological elastomers (MREs) to be added in silicone rubber matrix and carbonyl iron particles (CIPs) as their filler. The CIPs were fixed at 60 wt% and two types of MREs sample were fabricated which are isotropic and anisotropic. Rheological properties related to shear storage modulus were measured using a rheometer (MCR 302, Anton Paar). The experimental results demonstrated that the magnetorheological (MR) effect of anisotropic MREs-based Silicone/SAIB was 126 % as compared to isotropic MREs-based Silicone/SAIB, 64%. The fabricated MREs samples were frequency and strain dependent. The relative MR effect for both samples showed decreasing trend with the increment of strain amplitude and excitation frequency.

scholarly journals Physicochemical characterization and rheological properties of magnetic elastomers containing different shapes of corroded carbonyl iron particles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nurul Liyana Burhannuddin ◽  
Nur Azmah Nordin ◽  
Saiful Amri Mazlan ◽  
Siti Aishah Abdul Aziz ◽  
Noriyuki Kuwano ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Carbonyl Iron ◽  
Physicochemical Characterization ◽  
Milling Process ◽  
Iron Particles ◽  
Accelerated Corrosion ◽  
Field Dependent ◽  
Accelerated Corrosion Test ◽  
Different Shapes

AbstractCarbonyl iron particles (CIPs) is one of the key components in magnetic rubber, known as magnetorheological elastomer (MRE). Apart from the influence of their sizes and concentrations, the role of the particle’ shape is pronounced worthy of the attention for the MRE performance. However, the usage of CIPs in MRE during long-term applications may lead to corrosion effects on the embedded CIPs, which significantly affects the performance of devices or systems utilizing MRE. Hence, the distinctions between the two types of MRE embedded in different shapes of spherical and plate-like CIPs, at both conditions of non-corroded and corroded CIPs were investigated in terms of the field-dependent rheological properties of MRE. The plate-like shape was produced from spherical CIPs through a milling process using a rotary ball mill. Then, both shapes of CIPs individually subjected to an accelerated corrosion test in diluted hydrochloric (HCl) at different concentrations, particularly at 0.5, 1.0, and 1.5 vol.% for 30 min of immersion time. Eight samples of CIPs, including non-corroded for both CIPs shapes, were characterized in terms of a morphological study by field emission scanning electron microscope (FESEM) and magnetic properties via vibrating sample magnetometer (VSM). The field-dependent rheological properties of MREs were analyzed the change in the dynamic modulus behavior of MREs via rheometer. From the application perspective, this finding may be useful for the system to be considered that provide an idea to prolong the performance MRE by utilizing the different shapes of CIPs even when the material is fading.

scholarly journals Effect of Photoinitiator on Precursory Stability and Curing Depth of Thiol-Ene Clickable Gelatin

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1877
Author(s):  
Kai-Hung Yang ◽  
Gabriella Lindberg ◽  
Bram Soliman ◽  
Khoon Lim ◽  
Tim Woodfield ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Visible Light ◽  
Rheological Properties ◽  
Swelling Ratio ◽  
Sodium Persulfate ◽  
Photo Polymerization ◽  
Gelation Kinetics ◽  
The Stability ◽  
Over Time

Recent advances highlight the potential of photopolymerizable allylated gelatin (GelAGE) as a versatile hydrogel with highly tailorable properties. It is, however, unknown how different photoinitiating system affects the stability, gelation kinetics and curing depth of GelAGE. In this study, sol fraction, mass swelling ratio, mechanical properties, rheological properties, and curing depth were evaluated as a function of time with three photo-initiating systems: Irgacure 2959 (Ig2959; 320–500 nm), lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP; 320–500 nm), and ruthenium/sodium persulfate (Ru/SPS; 400–500 nm). Results demonstrated that GelAGE precursory solutions mixed with either Ig2959 or LAP remained stable over time while the Ru/SPS system enabled the onset of controllable redox polymerization without irradiation during pre-incubation. Photo-polymerization using the Ru/SPS system was significantly faster (<5 s) compared to both Ig2959 (70 s) and LAP (50 s). Plus, The Ru/SPS system was capable of polymerizing a thick construct (8.88 ± 0.94 mm), while Ig2959 (1.62 ± 0.49 mm) initiated hydrogels displayed poor penetration depth with LAP (7.38 ± 2.13 mm) in between. These results thus support the use of the visible light based Ru/SPS photo-initiator for constructs requiring rapid gelation and a good curing depth while Ig2959 or LAP can be applied for photo-polymerization of GelAGE materials requiring long-term incubation prior to application if UV is not a concern.

scholarly journals Analysis of Styrene-Butadiene Based Thermoplastic Magnetorheological Elastomers with Surface-Treated Iron Particles

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1597
Author(s):  
Arturo Tagliabue ◽  
Fernando Eblagon ◽  
Frank Clemens
Keyword(s):  
Shear Modulus ◽  
Thermoplastic Elastomers ◽  
Phosphate Coating ◽  
Iron Particles ◽  
Pressing Method ◽  
Magnetorheological Elastomers ◽  
Fused Deposition ◽  
Mr Effect ◽  
Styrene Butadiene ◽  
Dynamic Mr

Magnetorheological elastomers (MRE) are increasing in popularity in many applications because of their ability to change stiffness by applying a magnetic field. Instead of liquid-based 1 K and 2 K silicone, thermoplastic elastomers (TPE), based on styrene-butadiene-styrene block copolymers, have been investigated as matrix material. Three different carbonyl iron particles (CIPs) with different surface treatments were used as magneto active filler material. For the sample fabrication, the thermoplastic pressing method was used, and the MR effect under static and dynamic load was investigated. We show that for filler contents above 40 vol.-%, the linear relationship between powder content and the magnetorheological effect is no longer valid. We showed how the SiO2 and phosphate coating of the CIPs affects the saturation magnetization and the shear modulus of MRE composites. A combined silica phosphate coating resulted in a higher shear modulus, and therefore, the MR effect decreased, while coating with SiO2 only improved the MR effect. The highest performance was achieved at low deformations; a static MR effect of 73% and a dynamic MR effect of 126% were recorded. It was also shown that a lower melting viscosity of the TPE matrix helps to increase the static MR effect of anisotropic MREs, while low shear modulus is crucial for achieving high dynamic MR. The knowledge from TPE-based magnetic composites will open up new opportunities for processing such as injection molding, extrusion, and fused deposition modeling (FDM).

Organophosphorus compounds: a hidden threat to the health and wellbeing of mankind

2020 ◽  
pp. 38-60
Author(s):  
Konstantin Gorbunov ◽  
Denis Gudkov
Keyword(s):  
Cognitive Impairment ◽  
Chronic Exposure ◽  
Organophosphorus Compounds ◽  
Acute Poisoning ◽  
Chronic Intoxication ◽  
Health And Wellbeing ◽  
Children Development ◽  
External Stimuli ◽  
Modern Technologies

Organophosphorus compounds (OPC) have been known for about 90 years: drugs and pesticides, poisons causing paralysis, convulsions and death in case of acute poisoning and leading to cancer, malformations and cognitive impairment in case of chronic exposure by doses that do not cause acute intoxication. Despite the existing measures, deaths due to OPC poisoning are recorded annually. The problem of children development after any poisoning even with small doses of these substances is especially urgent. Modern technologies provide new perspectives for the analysis of chronic intoxication by OPC, prognosis of acute poisoning severity and long-term health consequences. Research of miRNA and metabolomics came to the first place among the scientific approaches to the study of the body’s response to various external stimuli, including OPC poisoning. New methods are being developed to prevent the effects of poisoning based on stabilized bacterial enzymes, as well as modified miRNA.

Stimulus configuration, long-term potentiation, and the hippocampus

1997 ◽  
Vol 20 (4) ◽  
pp. 629-631 ◽  
Author(s):  
Nestor A. Schmajuk
Keyword(s):  
Neural Network ◽  
Computer Simulations ◽  
Neural Network Model ◽  
Long Term Potentiation ◽  
Stimulus Configuration ◽  
Association Cortex ◽  
Hippocampal Function ◽  
Term Potentiation ◽  
External Stimuli

Shors & Matzel propose that hippocampal LTP increases the effective salience of discrete external stimuli and thereby facilitates the induction of memories at distant places. In line with this suggestion, a neural network model of associative learning and hippocampal function assumes that LTP increases hippocampal error signals to the cortex, thereby facilitating stimulus configuration in association cortex. Computer simulations show that under these assumptions the model correctly describes the effect of LTP induction and blockade in classical discriminations and place learning.

scholarly journals Simulations of Learning, Memory, and Forgetting Processes with Model of CA1 Region of the Hippocampus

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Dariusz Świetlik
Keyword(s):  
Hardware Implementation ◽  
Pyramidal Cells ◽  
Coincidence Detection ◽  
High Rate ◽  
Synaptic Potentiation ◽  
Postsynaptic Potentials ◽  
Ca1 Region ◽  
Analog Memory ◽  
External Stimuli

The aim of this paper is to present a computational model of the CA1 region of the hippocampus, whose properties include (a) attenuation of receptors for external stimuli, (b) delay and decay of postsynaptic potentials, (c) modification of internal weights due to propagation of postsynaptic potentials through the dendrite, and (d) modification of weights for the analog memory of each input due to a pattern of long-term synaptic potentiation (LTP) with regard to its decay. The computer simulations showed that CA1 model performs efficient LTP induction and high rate of sub-millisecond coincidence detection. We also discuss a possibility of hardware implementation of pyramidal cells of CA1 region of the hippocampus.

Field-induced anti-nematic and biaxial ordering in binary mixtures of discotic mesogens and spherical magnetic nanoparticles

Soft Matter ◽  
2020 ◽  
Vol 16 (47) ◽  
pp. 10667-10675
Author(s):  
Stavros D. Peroukidis ◽  
Sabine H. L. Klapp ◽  
Alexandros G. Vanakaras
Keyword(s):  
Magnetic Nanoparticles ◽  
Binary Mixtures ◽  
Computer Simulations ◽  
Liquid Crystalline ◽  
Magnetic Particles ◽  
Equilibrium Structure ◽  
Discotic Mesogens ◽  
External Stimuli

Using computer simulations we explore the equilibrium structure and response to external stimuli of complex magnetic hybrids consisting of magnetic particles in discotic liquid crystalline matrices.

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