Poly Methyl Methacrylate Particles Research Articles

Controlled soap-free emulsion polymerization stability using a novel cationic azo radical initiator with chloride or triflate counter anion

In our previous work, we developed a novel cationic azo radical initiator, 2,2′-azobis-[2-(1,3-dimethyl-4,5-dihydro-1H-imidazol-3-ium-2-yl)]propane triflate (ADIP) to prepare cationic and hydrophilic polymer particles for incorporation into cells. To apply this cationic radical initiator to hydrophobic polymer particles for a broader range of industrial applications, we attempted to synthesize polymethylmethacrylate (PMMA) latex via surfactant-free emulsion polymerization (SFEP). However, we found that the synthesized emulsion coagulated and contained a wide-size distribution of the particles, resulting in the failure of stable emulsion polymerization. In this study, we have successfully synthesized cationic PMMA particles with a narrow size distribution without any coagulation using ADIP-Cl which is an ADIP derivative in which the triflate counter anion was replaced with chloride. Compared to other halides and polyatomic anions, the triflate anion caused a significant aggregation of the PMMA particles. Furthermore, we confirmed that ADIP-Cl can be also applicable for the size-controlled synthesis of PMMA nanoparticles with sub-100 nm size in an acetone-water mixture. We envision that polymer particles prepared by ADIP-Cl via SFEP can contribute to the design of various functional materials.

Microplastic-associated trophic transfer of benzo(k)fluoranthene in a limnic food web: Effects in two freshwater invertebrates (Daphnia magna, Chironomus riparius) and zebrafish (Danio rerio)

The continuously growing plastic production and incomplete recycling processes open manifold entry routes for microplastic particles (MPs) into the environment. Since knowledge on trophic transfer of contaminants sorbed to MPs is still insufficient for freshwater systems, the transfer of the model pollutant benzo(k)fluoranthene (BkF) sorbed to polymethyl methacrylate (PMMA) particles in a limnic food web was investigated: Two freshwater invertebrates (Daphnia magna and Chironomus riparius larvae) were selected and either left untreated, exposed to pristine PMMA, PMMA-associated BkF, or exposed to dissolved BkF (BkFaq). As second-level consumers, zebrafish (Danio rerio) were fed twice daily with pre-treated invertebrates over two days. Induction of hepatic cytochrome P450 by BkF was determined as 7-ethoxy-O-resorufin deethylase (EROD) activity. Both invertebrate species readily ingested PMMA particles, tracked via fluorescence microscopy and accumulated BkFaq, measured via GC–MS. Fluorescence signals in gastrointestinal tracts of zebrafish were quantified with confocal laser scanning microscopy (CLSM). The fluorescence signal in gastrointestinal tracts of zebrafish was not altered, whereas, EROD activity was significantly induced when zebrafish were fed with Chironomus riparius, pre-exposed to BkFaq. Trophic exposure scenarios with BkF sorbed to PMMA did not result in any alterations of investigated endpoints in both invertebrate species and zebrafish compared to controls. Given that BkF amounts were in the low ng-range, as detected by GC–MS, the transport of MP-sorbed BkF to zebrafish was less effective than direct exposure to waterborne BkFaq, and the potential threat of trophic transfer of substances such as BkF in limnic food webs may have been overestimated.

Spontaneous immobilization of both a fluorescent dye and a functional sugar during the fabrication of submicron-sized PMMA particles in an aqueous solution

Fluorescent particles with sugar chains immobilized on the particle surface are expected to be widely used as a fluorescent probe for biomaterial imaging and a fluorescent label for cell imaging as well as a highly accurate detection tool for toxic proteins and pathogenic viruses. Based on the expectation, a facile and environmentally friendly method for the one-pot incorporation of a fluorescent dye and alkylated functional sugar molecules during the fabrication of submicron-sized polymethyl methacrylate (PMMA) particles was established in the present work. This method used coumarin 7 as a hydrophobic fluorescent dye and octyl-β-d-glucopyranoside (octyl-glc), in which an octyl group is glycoside bound to a glucose skeleton, as a functional sugar. During PMMA particle formation by soap-free emulsion polymerization, coumarin 7 was spontaneously incorporated into the PMMA particles. At the same time, due to its hydrophobicity, the octyl group entered the PMMA particles, and due to its hydrophilicity, the glucose was in contact with the water medium. The immobilization of octyl-glc on the particle surfaces was evaluated using concanavalin A (ConA) as a lectin, which has a selective affinity for glucose. It was found that the characteristics of fluorescence and ConA adsorption were maintained, even after immersing the sugar-immobilized fluorescent PMMA particles in water for one and a half years, indicating that coumarin 7 was retained inside the PMMA particles, and octyl-glc was stably immobilized for a long time on the surface layer of the PMMA particle by using an octyl group as an anchor. Furthermore, as shown by the confocal laser scanning microscopy images of the water-dispersed particles, coumarin 7 was incorporated into almost all the particles, which were dispersed without aggregation in water, indicating that the sugar-immobilized fluorescent PMMA particles enable high-accuracy fluorescence analysis and imaging.

Effective uptake of submicrometre plastics by crop plants via a crack-entry mode

Most microplastics are emitted, either directly or via the degradation of plastics, to the terrestrial environment and accumulate in large amounts in soils, representing a potential threat to terrestrial ecosystems. It is very important to evaluate the uptake of microplastics by crop plants because of the ubiquity of microplastics in wastewaters often used for agricultural irrigation worldwide. Here, we analyse the uptake of different microplastics by crop plants (wheat (Triticum aestivum) and lettuce (Lactuca sativa)) from treated wastewater in hydroponic cultures and in sand matrices or a sandy soil. Our results provide evidence in support of submicrometre- and micrometre-sized polystyrene and polymethylmethacrylate particles penetrating the stele of both species using the crack-entry mode at sites of lateral root emergence. This crack-entry pathway and features of the polymeric particles lead to the efficient uptake of submicrometre plastic. The plastic particles were subsequently transported from the roots to the shoots. Higher transpiration rates enhanced the uptake of plastic particles, showing that the transpirational pull was the main driving force of their movement. Our findings shed light on the modes of plastic particle interaction with plants and have implications for crops grown in fields contaminated with wastewater treatment discharges or sewage sludges. The presence of microplastics in wastewaters used for irrigation highlights the urgency of analysing the possible uptake of microplastics by crop plants. This study shows that submicrometre and micrometre plastic particles from treated wastewater enter the steles of crop plants via a crack entry at sites of lateral root emergence.

Mechanical, Thermal and Wear Behavior of SiC Particle Strengthening of PMMA-Toughened Glass-Epoxy Hybrid Composite

The effect of silicon carbide (SiC) particle strengthening on polymethyl methacrylate (PMMA)-toughened glass-epoxy composite has been studied. The primary aim of this research is two different tasks. Studying the effect of PMMA toughening on glass-epoxy composite and the effect of SiC particle addition are the two tasks. The PMMA and SiC particles are dispersed with epoxy resin at room temperature and composites are prepared using hand layup method. The composites were subjected for post cured at 80οC for better performance. The tensile and flexural results showed that the addition of PMMA and SiC improved the tensile, flexural strength and modulus. Similarly, the TGA of PMMA toughened glass-epoxy composite shows higher mass loss whereas; SiC addition retains the temperature stability. The specific wear rate and coefficient of friction (COF) showed that the composites inbuilt with SiC content offered lower sp. wear rate and COF of 0.024 and 0.5. The scanning electron microscopy (SEM) micrographs explicated more shear cups and striations, which indicates improved toughness of composites.

Evaluation of some properties of recycled polymethylmethacrylate incorporated to the acrylic resin

Many attempts have been made enhancing properties of PMMA denture base material. Adding fillers to PMMA was a commonly used method to improve physical and mechanical properties. To estimate the effects of incorporating recycled polymethylmethacrylate with a different percentage with conventional heat-cured acrylic resin on some properties of heat-cured denture base resin. The recycled polymethylmethacrylate (Chaini-HK G) particles dissolved at (5%,10%,15%) was added to heat-cured polymethylmethacrylate (Spofadental, Czech Republic) polymer and mixed with a ratio of 2:1 with the polymethylmethacrylate monomer. A total number of specimens were 80, which divided into three experimental groups (5%, 10%, 15%) and control group. Each group have 20specimens. The surface hardness, water sorption, solubility and residual monomer of test groups measured as well as compared to that of control groups. Fourier transform infrared spectroscopy test (FTIR) was done for three experimental and control group. This study shows a statistically significant difference at (p<0.01) in the hardness of recycled polymethylmethacrylate incorporate material (10 %,15%) groups when compared with a control group; while recycled polymethylmethacrylate incorporated (5%) group show no significant difference, group with 15% shows the highest Vickers hardness value. The mean values of water sorption test solubility test and residual monomer were decreased with the increase of incorporating a percentage of recycled polymethylmethacrylate as compared to the mean value of the control group. The incorporation of recycled polymethylmethacrylate to heat acrylic resin at different percentage improves some of its properties.

Application of Positron Emission Particle Tracking (PEPT) to measure the bubble-particle interaction in a turbulent and dense flow

In a flotation cell, turbulence influences the motion of solid particles relative to the bubble surface, and, thus, affects the recovery rate. But, the impact of turbulence on the probability of a bubble-particle aggregation is still difficult to measure, especially in a dense flow. Therefore, the focus of this work was to apply Positron Emission Particle Tracking (PEPT) as a method to investigate the effect of turbulence on the particle movement and bubble-particle interaction in an opaque flow. Single air bubbles (db=2.5mm) were generated on a needle in a water flow channel. Upstream, a grid produced an isotropic turbulent flow with 5% to 15% turbulence intensity and a Kolmogorov microscale of 20 µm. Depending on the distance to the grid, the flow near the captive bubble (Reb=450) was characterized by eddies of different length scales and magnitude with tomographic Particle Image Velocimetry (PIV). The solid suspension contained up to 0.3% polymethylmethacrylate (PMMA) particles (dp=200–400μm) and up to six radiolabelled particles (dp=300–400μm) coated with PMMA. The trajectories of the labelled particles were used to determine the average particle distribution in the turbulent field and describe the bubble-particle interactions. These results provide valuable information on the applicability of PEPT in turbulent and dense flow fields as well as on particle trajectories close to bubbles, enhancing our understanding of key flotation phenomena.

Secondary particle formation in suspension polymerization using a particulate surfactant

ABSTRACT Suspension polymerization is widely used for the preparation of microsphere and microcapsules for many applications. However, the formation of secondary particle byproducts decreases drastically the obtained microsphere yield and microcapsule shell strength. It is surprisingly finding that the secondary particles were not observed in the preparation of polymethyl methacrylate particles by suspension polymerization using particulate surfactant called Pickering emulsion. Therefore, in this work, the mechanism of secondary particle formation during suspension polymerization was investigated using various surfactants (zinc oxide, titanium dioxide, and silica nanoparticles compared to polyvinyl alcohol) and monomers (styrene, methyl methacrylate, and methyl acrylate) with different water solubilities. Results showed that submicrometer-sized secondary particles were still formed by homogeneous nucleation mainly due to radical exit from the monomer droplets. However, the formed secondary particles were unstable and then adsorbed on the main microsphere surface. The number of secondary particles increased when monomers with higher water solubility were used.

Luminescence interference to two-colour toluene laser-induced fluorescence thermometry in a particle-laden flow

We present the use of two-colour toluene planar laser-induced fluorescence (LIF) to obtain spatially resolved measurements of the gas temperature ($$T_\mathrm{g}$$) in a particle-laden turbulent flow under sufficiently dense particle loading that the interference from laser interactions with the particles is significant. The effect of the ratio of volumetric flow rates of the particle phase to the gas phase ($$\phi$$) on the accuracy and precision of two-colour toluene LIF thermometry was systematically investigated for three particle materials, alumina, zinc activated zinc oxide (ZnO:Zn) and polymethyl methacrylate (PMMA), each of which has differing interactions with the excitation laser. The PMMA particles were spherical and mono-disperse with diameters of 6 to $$40\, \upmu \hbox {m}$$, while the alumina and ZnO:Zn particles had diameters in the range 1–40 $$\upmu \hbox {m}$$ and 2–200 $$\upmu \hbox {m},$$ respectively. The results show that the accuracy of the gas temperature measurement is insensitive to particle size for the PMMA particles, but dependent on the instantaneous particle loading. Importantly, reliable measurements can be performed in the dense two-way coupling regime, with the measurement being accurate to within 5 °C for $$\phi$$ < $$2.5\times 10^{-4}$$ for the PMMA particles and for $$\phi<$$$$7.6\times 10^{-4}$$ for the alumina and ZnO:Zn particles.

Effect of size disparity on the structure and dynamics of the small component in concentrated binary colloidal mixtures.

We determined, using confocal microscopy, the structure and dynamics of the small component in concentrated binary colloidal mixtures with moderate and large size ratios and different compositions of Polymethyl methacrylate particles. We show that when increasing the content of small spheres at fixed total volume fraction, a transition in the local environment of the small particles is observed, from a mixed environment of other small and large particles to a local environment of only small particles. The transition is rather abrupt for moderate size ratios, while it becomes particularly broad for large size ratios. This can be associated with the improved ability of the small particles to pack in between the large particles for larger size ratios. The dynamics reflect the transition with an increase of the mobility observed at intermediate mixing. This increase becomes particularly pronounced for large size ratios, leading to diffusive dynamics of the small particles, in agreement with predictions of theories of the glass transition in binary hard-sphere mixtures. The composition at which the fastest dynamics are observed is apparently independent of the size ratio.

Electrolytic Zinc Composite Coatings: Ultrasound Assisted Deposition for Morphological and Composition Modification

Protection of steel by sacrificial coatings is of primary importance in the industry, to extend the lifetime of steel structure parts. This is frequently obtained by zinc coatings, after galvanization or electrodeposition, but pure zinc is sometimes not resistant enough when high protective properties are required. Indeed, zinc corrosion rate is quite important, even if corrosion products play an important role in protection. Therefore, Zn alloys deposition is a privileged process. However, the metallic alloy elements used for codeposition are frequently composed of harmful substances, which use is more and more regulated. In a global strategy of employees and environment protection, and to anticipate more drastic restriction, the European plating shop leader Electropoli proposed a partnership to the research institute UTINAM. The project Zincadher intended to propose an alternative to zinc alloys plating by a zinc matrix, reinforced by silica and PMMA particles which main function is to increase corrosion resistance and adhesion. To overcome the lack of availability of PMMA (poly (methyl methacrylate)) nanoparticles at a reasonable price, an original synthesis of the PMMA particles was first developed [1]. It involves the use of a custom-made ultrasonic system, were MMA (methyl methacrylate) and water mixtures are exposed to different ultrasonic systems and successive sonication steps as follows: 20 kHz → 580 kHz → 858 kHz → 1138 kHz. Then, polymerization of the droplets is conducted, in order to obtain the largest possible concentration of PMMA particles of sub micrometer size range of different electrokinetic properties [2]. In a second part of the study, electrochemical study of acid zinc electrolyte with PMMA and/or silica particle have been carried out. As ultrasound is known to improve greatly mass transfer and coating characteristics as well as particles dispersion [3], a calibration of acoustic streaming at the surface of the working electrode is conducted, to be able to compare with classical mechanical stirring with the concept of equivalent velocity. Then, after particles dispersion in an acid zinc bath, composite coatings are elaborated. The plating parameters (current density, particles nature, hydrodynamic source…) on the morphology and composition of the coatings are evaluated by SEM/EDS and XRD characterization. Acknowledgement: The authors would like to thank Electropoli Group for funding this project and the ANRT for the CIFRE convention. [1] K. Nakabayashi, T. Fuchigami, M. Atobe, Electrochimica Acta. 110 593–598 (2013) [2] L Baissac, CC Buron, L Hallez, P Berçot, JY Hihn, L Chantegrel, G Gosse Ultrasonics sonochemistry 40, 183-192 (2018) [3] JY Hihn, F Touyeras, ML Doche, C Costa, BG Pollet in Power Ultrasound in Electrochemistry: From Versatile Laboratory Tool to Engineering Solution, John Wiley & Sons, Ltd, 169-214 (2012) Figure 1

Solochrome cyanine: A histological stain for cobalt-chromium wear particles in metal-on-metal periprosthetic tissues

Metal-on-metal (MoM) hip arthroplasties produce abundant implant-derived wear debris composed mainly of cobalt (Co) and chromium (Cr). Cobalt-chromium (Co-Cr) wear particles are difficult to identify histologically and need to be distinguished from other wear particle types and endogenous components (e.g., haemosiderin, fibrin) which may be present in MoM periprosthetic tissues. In this study we sought to determine whether histological stains that have an affinity for metals are useful in identifying Co-Cr wear debris in MoM periprosthetic tissues. Histological sections of periprosthetic tissue from 30 failed MoM hip arthroplasties were stained with haematoxylin-eosin (HE), Solochrome Cyanine (SC), Solochrome Azurine (SA) and Perls’ Prussian Blue (PB). Sections of periprosthetic tissue from 10 cases of non-MoM arthroplasties using other implant biomaterials, including titanium, ceramic, polymethylmethacrylate (PMMA) and ultra-high molecular weight polyethylene (UHMWP) were similarly analysed. Sections of 10 cases of haemosiderin-containing knee tenosynovial giant cell tumour (TSGCT) were also stained with HE, SC, SA and PB. In MoM periprosthetic tissues, SC stained metal debris in phagocytic macrophages and in the superficial necrotic zone which exhibited little or no trichrome staining for fibrin. In non-MoM periprosthetic tissues, UHMWP, PMMA, ceramic and titanium particles were not stained by SC. Prussian Blue, but not SC or SA, stained haemosiderin deposits in MoM periprosthetic tissues and TSGT. Our findings show that SC staining (most likely Cr-associated) is useful in distinguishing Co-Cr wear particles from other metal/non-metal wear particles types in histological preparations of periprosthetic tissue and that SC reliably distinguishes haemosiderin from Co-Cr wear debris.

One-pot formation of sugar-immobilized monodisperse polymethylmethacrylate particles by soap-free emulsion polymerization

Soap-free emulsion polymerization was applied to fabricate monodisperse submicron-sized polymethylmetacrylate (PMMA) particles with β-D-glucopyranoside (glucose) groups immobilized on the surface. The immobilization was induced not by the direct surface chemical modification but rather by the coexistence of octyl-β-D-glucopyranoside dissolved in the starting water solvent. The presence of the immobilized glucose components on the particle surface was proven by the specific affinity for concanavalin A (ConA). Due to the hydrophobic nature of the PMMA matrix, the relatively hydrophilic glucose components tend to be oriented toward the outer aqueous phase, giving rise to the markedly increased adsorption of ConA, where the nonpolar octyl tail acts as the anchor to the relatively hydrophobic polymeric matrix.

Inflammatory Responses Reprogram TREGS Through Impairment of Neuropilin-1

Chronic inflammatory insults compromise immune cell responses and ultimately contribute to pathologic outcomes. Clinically, it has been suggested that bone debris and implant particles, such as polymethylmethacrylate (PMMA), which are persistently released following implant surgery evoke heightened immune, inflammatory, and osteolytic responses that contribute to implant failure. However, the precise mechanism underlying this pathologic response remains vague. TREGS, the chief immune-suppressive cells, express the transcription factor Foxp3 and are potent inhibitors of osteoclasts. Using an intra-tibial injection model, we show that PMMA particles abrogate the osteoclast suppressive function of TREGS. Mechanistically, PMMA particles induce TREG instability evident by reduced expression of Foxp3. Importantly, intra-tibial injection of PMMA initiates an acute innate immune and inflammatory response, yet the negative impact on TREGS by PMMA remains persistent. We further show that PMMA enhance TH17 response at the expense of other T effector cells (TEFF), particularly TH1. At the molecular level, gene expression analysis showed that PMMA particles negatively regulate Nrp-1/Foxo3a axis to induce TREG instability, to dampen TREG activity and to promote phenotypic switch of TREGS to TH17 cells. Taken together, inflammatory cues and danger signals, such as bone and implant particles exacerbate inflammatory osteolysis in part through reprogramming TREGS.

Drop impacting on a single layer of particles: Evolution of ring without particles

In this study, we examined the impacts of a millimeter sized water drop hitting a layer of uniformly distributed particles on a hydrophilic/hydrophobic glass slide. A ring/disc structure without particles was formed and modified by two mechanisms: pushout and pullback. The pushout factor dominated the process when the drop hit on the hydrophilic glass slide, while the pullback factor played a decisive role during impact on the hydrophobic surface. The rebound of a drop on the hydrophobic surface formed a disc-shaped ring. We showed that the ratio of the effects of these two factors on the ring/disc width were independent from the impact speed, in both experimental and scaling analyses. Our results also suggested that higher hydrophobicity of a water drop on the hydrophobic glass slide, instead of a polymethyl methacrylate (PMMA) particle surface, resulted in a lower maximum spreading distance when the drop hit the PMMA particle layer on a hydrophobic surface.

Targeting vascular endothelial growth factor ameliorates PMMA-particles induced inflammatory osteolysis in murine calvaria.

Cytokines and growth factors mediate inflammatory osteolysis in response to particles released from bone implants. However, the mechanism by which this process develops is not entirely clear. Blood vessels and related factors may be required to deliver immune cells and soluble factors to the injury site. Therefore, in the current study we investigated if, vascular endothelial growth factor (VEGF), which is required for angiogenesis, mediates polymethylmethacrylate (PMMA) particles-induced osteolysis. Using bone marrow derived macrophages (BMMs) and ST2 stromal cell line, we show that PMMA particles increase VEGF expression. Further, using a murine calvarial osteolysis model, we found that PMMA injection over calvaria induce significant increase in VEGF expression as well as new vessel formation, represented by von Willebrand factor (vWF) staining. Co-treatment using a VEGF-neutralizing antibody abrogated expression of vWF, indicating decreased angiogenesis. Finally, VEGF neutralizing antibody reduced expression of Tumor necrosis factor (TNF) and decreased osteoclastogenesis induced by PMMA particles in calvariae. This work highlights the significance of angiogenesis, specifically VEGF, as key driver of PMMA particle-induced inflammatory osteolysis, inhibition of which attenuates this response.

Magnetoelectric effect in free-standing multiferroic thin film

We prepared two-dimensional close-packed hemispherical CoFe2O4(CFO)/Pb(Zr0.52Ti0.48O3)(PZT)/LaNiO3(LNO)/NiO thin film on Si(100) substrate using a template made of monodispersed polymethyl methacrylate (PMMA) particles. LNO and NiO layers are introduced for the bottom electrode and seed to crystallize, respectively. Since this hemispherical thin film is connected with the substrate only at the “foot” of the hemisphere, this thin film has a hollow structure. Therefore we call this structure as “free-standing” thin film. In this work, we also prepared planar CFO/PZT/LNO/NiO thin film on Si(100) substrate without using the PMMA template for comparison. In this work, we examined the effect of applying a vertical external magnetic field on the ferroelectric property. It was found that applying an external magnetic field decreases remanent polarization (Pr) for both planar and free-standing thin film. The degree of decrease of Pr in the free-standing thin film is about four times larger than that in the planar thin film. This indicates that large multiferroic property (interaction between ferromagnetic and ferroelectric) is realized in the free-standing thin film.

Intramedullary epinephrine and surgical hole on femoral cortex before intramedullary K-wire and bone cement insertion resulting in lower amount of PMMA (polymethyl methacrylate) particles on rabbit’s myocardium

Background: Cemented hip arthroplasty can result in devastating complication such as Bone Cement Implantation Syndrome (BCIS). BCIS consists of decreased blood pressure, decreased heart rate, a decrease of consciousness, and sudden death. This devastating condition caused by systemic circulation of polymethyl methacrylate (PMMA). Decrease heart rate caused by PMMA reaction with the heart muscle. PMMA reach heart muscle due to the increased intramedullary pressure and the opening of the intramedullary blood vessel during cementation. Aim: The purpose of this study is to prove that intramedullary epinephrine and femoral hole before the insertion of bone cement and K-wire result in the lower amount of PMMA in rabbit’s myocardium. Methods This research is conducted as experimental research with post-test only control group design with the subject rabbits. A total of 28 research subjects who met the inclusion criteria of the study were randomly divided into treatment and control groups. The control group did not receive epinephrine and femoral hole treatment. Treatment group 1 received epinephrine intramedullary only, treatment group 2 received femoral hole only, and treatment group 3 received intramedullary epinephrine and femoral hole. Results: Statistical analysis using parametric tests one-way ANOVA found a significant difference between treatment and control groups on the amount of rabbit’s heart muscle. The amount of PMMA particle in all treatment groups are lower than the control group with a p-value of 0.000 (p&lt;0.05). The amount of PMMA particle in treatment group 3 (received epinephrine and femoral hole) is lower than the control group with a p-value of 0.000 (p&lt;0.05). Conclusion: The conclusion of this research is intramedullary epinephrine and femoral hole making before the insertion of bone cement and K-wire result in the lower amount of PMMA particle in rabbit’s myocardiumÂ

A 3D STOCHASTIC MODEL FOR GEOMETRICAL CHARACTERIZATION OF PARTICLES IN TWO-PHASE FLOW APPLICATIONS

In this paper a new approach to geometrically model and characterize 2D silhouette images of two-phase flows is proposed. The method consists of a 3D modeling of the particles population based on some morphological and interaction assumptions. It includes the following steps. First, the main analytical properties of the proposed model – which is an adaptation of the Matérn type II model – are assessed, namely the effect of the thinning procedures on the population’s fundamental properties. Then, orthogonal projections of the model realizations are made to obtain 2D modeled images. The inference technique we propose and implement to determine the model parameters is a two-step numerical procedure: after a first guess of the parameters is defined, an optimization procedure is achieved to find the local minimum closest to the constructed initial solution. The method was validated on synthetic images, which has highlighted the efficiency of the proposed calibration procedure. Finally, the model was used to analyze real, i.e., experimentally acquired, silhouette images of calibrated polymethyl methacrylate (PMMA) particles. The population properties are correctly evaluated, even when suspensions of concentrated monodispersed and bidispersed particles are considered, hence highlighting the method’s relevance to describe the typical configurations encountered in bubbly flows and emulsions.

Properties of Porous Magnesium Using Polymethyl Methacrylate (PMMA) as a Space Holder

Porous magnesium has been recognized as a promising biodegradation metal for bone substitute application because of its excellent biocompatibility, low density, ability to biodegrade in vivo and excellent mechanical properties. In the present work, porous magnesium was fabricated by powder metallurgy using spherical polymethyl methacrylate (PMMA) as a space holder. To determine the optimum sintering temperature for porous magnesium fabrication, the porous magnesium was fabricated using double step sintering process at various sintering temperature (550°C, 585°C and 620°C) in first stage of research. The porous magnesium fabricated was then characterized for morphology, porosity, density and compressive strength. Density of porous magnesium increases and the porosity decreases with increasing sintering temperature. The mechanical characterization indicated that porous magnesium sintered at 620°C exhibited the highest compressive strength and density with optimum range of porosity of 39.37%. For second stage of research, porous magnesium with porosities of 39.38 – 40.82% was produced with different sizes of PMMA particles (38-63 µm, 63-90 µm and 90-125 µm). The compressive yield strength ranges between 19.95 MPa to 23.28 MPa and increases with decreasing PMMA particles size and porosity. These results proven that the PMMA has a potential to be used as space holder in porous magnesium for biomedical application.