Search results for: rigid polyurethane foam

Authors: Baofeng Pan, Heng Liu

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Because of the high strength and large carrying capacity, the semi-rigid base is widely used in modern road engineering. However, hydrodynamic pressure, which is one of the main factors to cause early damage of semi-rigid base, cannot be avoided in the nature environment when pavement is subjected to some loadings such as the passing vehicles. In order to investigating how moisture-induced-damage of semi-rigid base influenced by hydrodynamic pressure, a new and effective experimental research method is provided in this paper. The results show that: (a) The washing action of high hydrodynamic pressure is the direct cause of strength reducing of road semi-rigid base. (b) The damage of high hydrodynamic pressure mainly occurs at the beginning of the scoring test and with the increasing of testing time the influence reduces. (c) Under the same hydrodynamic pressure, the longer the specimen health age, the stronger ability to resist moisture induced damage.

Keywords: semi-rigid base, hydrodynamic pressure, moisture-induced-damage, experimental research

Procedia PDF Downloads 297

Authors: Jafar Akbari, Masoud Rismanchian, Samira Ramezani

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Purpose: The photocatalytic degradation of pollutants is a novel technology with various advantages such as high efficiency and energy saving. In this research, the effects of operational variables on the photocatalytic efficiency of TiO₂ coated on nickel foam in the removal of toluene from the simulated indoor air have been investigated. Methods: TiO₂ film were prepared via the sol-gel method and coated on nickel foam. The characteristics and morphology were found using XRD, SEM, and BET technique. Then, the effects of relative humidity, UV-A intensity, the initial toluene concentration, TiO₂ loading, and the air circulation velocity on the photocatalytic degradation rate have been evaluated. Results: The optimal degradation of toluene has been achieved with loading 4.35 g TiO2 on the foam, 30% RH, 5.4 µW.cm−2 UV-A intensity, and 20 ppm initial concentration in the air circulation velocity of 0.15 fpm. Conclusion: The changes of toluene photocatalytic degradation rate have been studied at various times. Also, the kinetic behavior of toluene photocatalytic degradation has been investigated using Langmuir-Hinshelwood (L-H) model.

Keywords: photocatalytic degradation, operational variables, tio₂, nickel foam, gaseous toluene, nanotechnology

Procedia PDF Downloads 57

Authors: Ploenpit Boochathum, Pitchayanad Kaolim, Phimjutha Srisangkaew

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In general, rubber foam is produced based on the sulfur curing system. However, the remaining sulfur in the rubber product waste is burned to sulfur dioxide gas causing the environment pollution. To avoid using sulfur as curing agent in the rubber foam products, this research work proposes non-sulfur curing system by using corn starch as a curing agent. The ether crosslinks were proposed to be produced via the functional bonding between hydroxyl groups of the starch molecules and chloroacetate groups added on the natural rubber molecules. The chloroacetated natural rubber (CNR) latex was prepared via the epoxidation reaction of the concentrated natural rubber latex, subsequently, epoxy rings were attacked by chloroacetic acid to produce hydroxyl groups and chloroacetate groups on the rubber molecules. Foaming agent namely NaHCO3 was selected to add in the CNR latex due to the low decomposition temperature at about 50°C. The appropriate curing temperature was assigned to be 90°C that is above gelatinization temperature; 60-70°C, of starch. The effect of weight ratio of starch, i.e., 0 phr, 3 phr and 5 phr, on the physical properties of CNR rubber foam was investigated. It was found that density reduced from 0.81 g/cm3 for 0 phr to 0.75 g/cm3 for 3 phr and 0.79 g/cm3 for 5 phr. The ability to return to its original thickness after prolonged compressive stresses of CNR rubber foam cured with starch loading of 5 phr was found to be considerably better than that of CNR rubber foam cured with starch 3 phr and CNR rubber foam without addition of starch according to the compression set that was determined to decrease from 66.67% to 40% and 26.67% with the increase loading of starch. The mechanical properties including tensile strength and modulus of CNR rubber foams cured using starch were determined to increase except that the elongation at break was found to decrease. In addition, all mechanical properties of CNR rubber foams cured with the starch 3 phr and 5 phr were found to be slightly different and drastically higher than those of CNR rubber foam without the addition of starch. This research work indicates that starch can be applicable as a curing agent for CNR rubber. This is confirmed by the increase of the elastic modulus (G') of CNR rubber foams that was cured with the starch over the CNR rubber foam without curing agent. This type of rubber foam is believed to be one of the biodegradable and environment-friendly product that can be cured at low temperature of 90°C.

Keywords: chloroacetated natural rubber, corn starch, non-sulfur curing system, rubber foam

Procedia PDF Downloads 278

Authors: Aylin Sahin, Yasemin Kilic, Abdulkadir Sari, Burcu Duymaz, Mustafa Kara

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Foam glass is an innovative material which composed of glass and carbon/carbonate based minerals; and has incomparable properties like light weight, high thermal insulation and cellular structure with sufficient rigidity. In the present study, the effects of the glass type and mineral addition on the foam glass properties were investigated. Nano sized SiC was fixed as foaming agent at the whole of the samples, mixed glass waste and sheet glass were selectively used as glass sources; finally Al₂O₃ was optionally used as mineral additive. These raw material powders were mixed homogenously, pressed at same pressure and sintered at same schedule. Finally, obtained samples were characterized based on the required properties of foam glass material, and optimum results were determined. At the end of the study, 0.049 W/mK thermal conductivity, 72 % porosity, and 0.21 kg/cm² apparent density with 2.41 MPa compressive strength values were achieved with using nano sized SiC, sheet glass and Al₂O₃ mineral additive. It can be said that the foam glass materials can be preferred as an alternative insulation material rather than polymeric based conventional insulation materials because of supplying high thermal insulation properties without containing unhealthy chemicals and burn risks.

Keywords: foam glass, foaming, silicon carbide, waste glass

Procedia PDF Downloads 336

Authors: Jianqin Qu

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This paper proposes a rigid point set matching algorithm in arbitrary dimensions based on the idea of symmetric covariant function. A group of functions of the points in the set are formulated using rigid invariants. Each of these functions computes a pair of correspondence from the given point set. Then the computed correspondences are used to recover the unknown rigid transform parameters. Each computed point can be geometrically interpreted as the weighted mean center of the point set. The algorithm is compact, fast, and dimension free without any optimization process. It either computes the desired transform for noiseless data in linear time, or fails quickly in exceptional cases. Experimental results for synthetic data and 2D/3D real data are provided, which demonstrate potential applications of the algorithm to a wide range of problems.

Keywords: covariant point, point matching, dimension free, rigid registration

Procedia PDF Downloads 146

Authors: Gui Yewei, Du Yanxia, Xiao Guangming, Liu Lei, Wei Dong, Yang Xiaofeng

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A phase change material (PCM) is a substance which absorbs a large amount of energy when undergoing a change of solid-liquid phase. The good physical and chemical properties of C or SiC foam reveal the possibility of using them as a thermal conductivity enhancer for the PCM. C or SiC foam composite PCM has a high effective conductivity and becomes one of the most interesting thermal storage techniques due to its advantage of simplicity and reliability. The paper developed a numerical method to simulate the heat transfer of SiC and C foam composite PCM, a finite volume technique was used to discretize the heat diffusion equation while the phase change process was modeled using the equivalent specific heat method. The effects of the porosity were investigated based on the numerical method, and the effects of the geometric model of the microstructure on the equivalent thermal conductivity was studies.

Keywords: SiC foam, composite, phase change material, heat transfer

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Authors: Anika Zafiah M. Rus, S. Shafizah

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This study was developed to compare the behavior and the ability of polymer foam composites towards sound absorption test of Shorea leprosula wood (SL) of acid hydrolysis treatment with particle size < 355µm. Three different weight ratio of polyol to wood particle has been selected which are 10wt%, 15wt%, and 20wt%. The acid hydrolysis treatment is to optimize the surface interaction of a wood particle with polymer foam matrix. In addition, the acoustic characteristic of sound absorption coefficient (Į) was determined. Further treatment is to expose the polymer composite in UV irradiation by using UV-Weatherometer. Polymer foam composite of untreated shorea leprosula particle (SL-B) with respective percentage loading shows uniform pore structure as compared with treated wood particle (SL-A). As the filler percentage loading in polymer foam increases, the Į value approaching 1 for both samples. Furthermore, SL-A shows better Į value at 3500-4500 frequency absorption level(Hz), meanwhile Į value for SL-B is maximum at 4000-5000 Hz. The frequencies absorption level for both SL-B and SL-A after UV exposure was increased with the increasing of exposure time from 0-1000 hours. It is, therefore, concluded that the Į for each sound absorbing material, with or without acid hydrolysis treatment of wood particles and it’s percentages loading in polymer matrix effect the sound absorption behavior.

Keywords: polymer foam composite, sound absorption coefficient, UV-irradiation, wood

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Authors: Pajaree Donkhampa, Fuangfa Unob

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Ceftazidime is an antibiotic drug commonly used to treat several human and veterinary infections. However, the presence of ceftazidime residues in the environment may induce microbial resistance and cause side effects to humans. Therefore, monitoring the level of ceftazidime in environmental resources is important. In this work, a melamine foam platform was proposed for simultaneous extraction and colorimetric detection of ceftazidime based on the azo dye formation on the surface. The melamine foam was chemically modified with polyethyleneimine (PEI) and characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Ceftazidime is a sample that was extracted on the PEI-modified melamine foam and further reacted with nitrite in an acidic medium to form an intermediate diazonium ion. The diazotized molecule underwent an azo coupling reaction with chromotropic acid to generate a red-colored compound. The material color changed from pale yellow to pink depending on the ceftazidime concentration. The photo of the obtained material was taken by a smartphone camera and the color intensity was determined by Image J software. The material fabrication and ceftazidime extraction and detection procedures were optimized. The detection of a sub-ppm level of ceftazidime was achieved without using a complex analytical instrument.

Keywords: colorimetric detection, ceftazidime, melamine foam, extraction, azo dye

Procedia PDF Downloads 152

Authors: Adrien Cornille, Marine Blain, Bernard Boutevin, Sylvain Caillol

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Generally, linear polyurethanes (PUs) are obtained by the reaction between an oligomeric diol, a short diol as chain extender and a diisocyanate. However the use of diisocyanate should be avoided since they are generally very harmful for human health. Therefore the synthesis of NIPUs (non isocyanate PUs) from step growth polymerization of dicyclocarbonates and diamines should be favoured. This method is particularly interesting since no hazardous isocyanates are used. Thus, this reaction, extensively studied by Endo et al. is currently gaining a lot of attention as a substitution route for the synthesis of NIPUs, both from industrial and academic community. However, the reactivity of reaction between amine and cyclic carbonate is a major scientific issue, since cyclic carbonates are poorly reactive. Thus, our team developed several synthetic ways for the synthesis of various di-cyclic carbonates based on C5-, C6- and dithio- cyclic carbonates, from different biobased raw materials (glycerin isosorbide, vegetable oils…). These monomers were used to synthesize NIPUs with various mechanical and thermal properties for various applications. We studied the reactivity of reaction with various catalysts and find optimized conditions for room temperature reaction. We also studied the radical copolymerization of cyclic carbonate monomers in styrene-acrylate copolymers for coating applications. We also succeeded in the elaboration of biobased NIPU flexible foams. To the best of our knowledge, there is no report in literature on the preparation of non-isocyanate polyurethane foams.

Keywords: foam, nonisocyanate polyurethane, cyclic carbonate, blowing agent, scanning electron microscopy

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Authors: Robel Legese Meko

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Natural fibers have been used as end-of-life textiles and made into textile products which have become a well-proven and effective way of processing. Nowadays, resources to make primary synthetic fibers are becoming less and less as the world population is rising. Hence it is necessary to develop processes to fabricate textiles that are easily converted to composite materials. Acoustic comfort is closely related to the concept of sound absorption and includes protection against noise. This research paper presents an experimental study on sound absorption coefficients, for natural fiber composite materials: a natural fiber (Coir/Jute) with different blend proportions of raw materials mixed with rigid polyurethane foam as a binder. The natural fiber composite materials were characterized both acoustically (sound absorption coefficient SAC) and also in terms of heat transfer (thermal conductivity). The acoustic absorption coefficient was determined using the impedance tube method according to the ASTM Standard (ASTM E 1050). The influence of the structure of these materials on the sound-absorbing properties was analyzed. The experimental results signify that the porous natural coir/jute composites possess excellent performance in the absorption of high-frequency sound waves, especially above 2000 Hz, and didn’t induce a significant change in the thermal conductivity of the composites. Thus, the sound absorption performances of natural fiber composites based on coir/jute fiber materials promote environmentally friendly solutions.

Keywords: coir/jute fiber, sound absorption coefficients, compression molding, impedance tube, thermal insulating properties, SEM analysis

Procedia PDF Downloads 75

Authors: Jichi Wu

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Though fast fashion and consumption do boost the economy and push the progress of the industry, they have also caused a mass of waste, which has led to great pressure on the environment. This project mainly focuses on how to develop new sustainable textile and fashion design through recycling, upcycling, and reusing. Substantial field researches were implemented from the very beginning, including collecting reusable material from recycling centers. Hot-pressed composite materials, hand-cutting, and weaving were finally selected as the core material/method of this project after attempts and experiments. Four pieces of menswear, as well as hats and other decorative products made from wasted foams and fabrics, were successfully manufactured. Results show that foam is not only possible for furniture but also for clothing. It helps people to realize that foam is warm, heatproof, anti-slippery, and crease-resistant. So, all advantages could inspire people that even common materials could have new usage and are worthy of upcycling.

Keywords: sustainable design, foam, upcycling, life cycle, textile design

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Authors: Rui Wang, Shanfa Tang, Yuanwu Dong, Siyao Wang

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A carboxylate Gemini surfactant N, N`-bis (3-chloro-2 -hydroxypropane-N-dodecyl secondary amine) p-phenylenediamine diacetate sodium (GD12-P-12) was synthesized by substitution and ring-opening reaction from p-phenylenediamine, sodium chloroacetate, epichlorohydrin, and dodecylamine. The synthesis conditions were optimized by controlling variables. The structure of GD12-P-12 was characterized by FT-IR and 1H NMR, and its foam performance, interfacial tension, viscosity was evaluated. The results show that the molecular structure of the synthesized product is consistent with that of the target product, the GD12-P-12 can reduce the oil-water interfacial tension to 7.49×10⁻³mN/m (ultra-low interfacial tension level) in 20min. GD12-P-12 surfactant has excellent foam performance, ultra-low interfacial tension, good temperature-resistant viscosity-increasing properties, has good application prospect in foam flooding.

Keywords: gemini surfactant, optimization of synthesis conditions, foam performance, low interfacial tension

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Authors: T. Poppendieker, H. Maurer, C. Segieth

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Over the past ten years, foam rolling has become a new trend in the fitness and health market. It is also a frequently used technique for self-massage. However, the scope of effects from foam rolling has only recently started to be researched and understood. The focus of this study is to examine the effects of prolonged foam rolling on muscle performance. Isometric muscle force was used as a parameter to determine an improving impact of the myofascial roller in two different application volumes. Besides the maximal muscle force, data were also collected on muscle activation during all tests. Twenty-four (17 females, 7 males) healthy students with an average age of 23.4 ± 2.8 years were recruited. The study followed a cross-over pre-/post design in which the order of conditions was counterbalanced. The subjects performed a one-minute and three-minute foam rolling application set on two separate days. Isometric maximal muscle force of the dominant calf was tested before and after the self-myofascial release application. The statistic software program SPSS 22 was used to analyze the data of the maximal isometric force of the calf muscle by a 2 x 2 (time of measurement x intervention) analysis of variance with repeated measures. The statistic significance level was set at p ≤ 0.05. Neither for the main effect of time of measurement (F(1,23) = .93, p = .36, f = .20) nor for the interaction of time of measurement x intervention (F(1,23) = 1.99, p = .17, f = 0.29) significant p-values were found. However, the effect size indicates a mean interaction effect with a tendency of greater pre-post improvements under the three-minute foam rolling condition. Changes in maximal force did not correlate with changes in EMG-activity (r = .02, p = .95 in the short and r = -.11, p = .65 in the long rolling condition). Results support findings of previous studies and suggest a positive potential for use of the foam roll as a means for keeping muscle force at least at the same performance level while leading to an increase in flexibility.

Keywords: application volume differences, foam rolling, isometric maximal force, self-myofascial release

Procedia PDF Downloads 262

Authors: Sabrina Boutaleb, Kouider Halim Benrahou, François Schosseler, Abdelouahed Tounsi, El Abbas Adda Bedia

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The use of polyurethane in different areas becomes more frequent. This is due to significant advantages they have including their lightness and resistance. However, their use requires a mastery of their mechanical performance. We will present in this work, a COAPUR 6050 which can be used to develop composite materials. COAPUR 6050 is an associative polyurethane thickener allowing fine rheological adjustment of flat or semi-gloss paints. COAPUR 6050 is characterised by its thickening efficiency at low shear rate. It is a solvent-free liquid product. It promotes good paint pick up, while maintaining a low yield point after shearing, and consequently a good levelling. We will then determine its rheological behaviour experimentally using different annular gaps. The rheological properties of COAPUR 6050 were researched by rotational rheometer (Rheometer-Mars III) using different annular gaps. There is the influence of the size of the annular gap on the behaviour as well as on the rheological parameters of the COAPUR 6050. The rheological properties data of COAPUR 6050 were regressed by nonlinear regression method and their rheological models were established, are characterized by yield pseudoplastic model. In this case, it is essential to make a viscometric correction. The latter was developed and presented in the experimental results.

Keywords: COAPUR 6050, flow’s couette, polyurethane, rheological behaviours

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Authors: Solomon Huluka, Akrum Abdul-Latif, Rachid Baleh

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Metal foams have been developed intensively as a new class of materials for the last two decades due to their unique structural and multifunctional properties. The aim of this experimental work was to characterize the effect of biaxial loading complexity (combined compression-torsion) on the plastic response of highly uniform architecture open-cell aluminum foams of spherical porous with a density of 80%. For foam manufacturing, the Kelvin cells model was used to generate the generally spherical shape with a cell diameter of 11 mm. A patented rig called ACTP (Absorption par Compression-Torsion Plastique), was used to investigate the foam response under quasi-static complex loading paths having different torsional components (i.e. 0°, 45° and 60°). The key mechanical responses to be examined are yield stress, stress plateau, and energy absorption capacity. The collapse mode was also investigated. It was concluded that the higher the loading complexity, the greater the yield strength and the greater energy absorption capacity of the foam. Experimentally, it was also noticed that there were large softening effects that occurred after the first pick stress for both biaxial-45° and biaxial-60° loading.

Keywords: aluminum foam, loading complexity, characterization, biaxial loading

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Authors: Virginia Martin Torrejon, Song Hang

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Gelatine foams are widely explored materials due to their biodegradability, biocompatibility, and availability. They exhibit outstanding properties and are currently subject to increasing scientific research due to their potential use in different applications, such as biocompatible cellular materials for biomedical products or biofoams as an alternative to fossil-fuel-derived packaging. Gelatine is a highly surface-active polymer, and its concentrated solutions usually do not require surfactants to achieve low surface tension. Still, anionic surfactants like sodium dodecyl sulfate (SDS) strongly interact with gelatine, impacting its viscosity and rheological properties and, in turn, their foaming behaviour. Foaming behaviour is a key parameter for cellular solids produced by mechanical foaming as it has a significant effect on the processing and properties of cellular materials. Foamability mainly impacts the density and the mechanical properties of the foams, while foam stability is crucial to achieving foams with low shrinkage and desirable pore morphology. This work aimed to investigate the influence of SDS on the foaming behaviour of concentrated gelatine foams by using a dynamic foam analyser. The study of maximum foam height created, foam formation behaviour, drainage behaviour, and foam structure with regard to bubble size and distribution were carried out in 10 wt% gelatine solutions prepared at different SDS/gelatine concentration ratios. Comparative rheological and viscometry measurements provided a good correlation with the data from the dynamic foam analyser measurements. SDS incorporation at optimum dosages and gelatine gelation led to highly stable foams at high expansion ratios. The viscosity increase of the hydrogel solution at SDS content increased was a key parameter for foam stabilization. In addition, the impact of SDS content on gelling time and gel strength also considerably impacted the foams' stability and pore structure.

Keywords: dynamic foam analyser, gelatine foams stability and foamability, gelatine-surfactant foams, gelatine-SDS rheology, gelatine-SDS viscosity

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Authors: Jaeseung Lee, Muhammad Faizan Chinannai, Mohamed Hassan Gundu, Hyunchul Ju

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In this paper, we numerically investigated the effect of metal foams on a real scale 242.57cm2 (19.1 cm × 12.7 cm) polymer electrolyte membrane fuel cell (PEFCs) using a three-dimensional two-phase PEFC model to substantiate design approach for PEFCs using metal foam as the flow distributor. The simulations were conducted under the practical low humidity hydrogen, and air gases conditions in order to observe the detailed operation result in the PEFCs using the serpentine flow channel in the anode and metal foam design in the cathode. The three-dimensional contours of flow distribution in the channel, current density distribution in the membrane and hydrogen and oxygen concentration distribution are provided. The simulation results revealed that the use of highly porous and permeable metal foam can be beneficial to achieve a more uniform current density distribution and better hydration in the membrane under low inlet humidity conditions. This study offers basic directions to design channel for optimal water management of PEFCs.

Keywords: polymer electrolyte fuel cells, metal foam, real-scale, numerical model

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Authors: Norazlin Mohamad, Saiful Adli Bukry, Zarina Zahari, Haidzir Manaf, Hanafi Sawalludin

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Background: Deficit in neuromuscular recruitment and decrease force distribution were the common problems among ankle instability patients due to altered joint kinematics that lead to recurrent ankle injuries. Rigid Tape and KT Tape had widely been used as therapeutic and performance enhancement tools in ankle stability. However the difference effect between this two tapes is still controversial. Objective: To investigate the different effect between Rigid Tape and KT Tape on force distribution and muscle activation among ankle instability patients while standing. Study design: Crossover trial. Participants: 27 patients, age between 18 to 30 years old participated in this study. All the subjects were applied with KT Tape & Rigid Tape on their affected ankle with 3 days of interval for each intervention. The subjects were tested with their barefoot (without tape) first to act as a baseline before proceeding with KT Tape, and then with Rigid Tape. Result: There were no significant difference on force distribution at forefoot and back-foot for both tapes while standing. However the mean data shows that Rigid Tape has the highest force distribution at back-foot rather than forefoot when compared with KT Tape that had more force distribution at forefoot while standing. Regarding muscle activation (Peroneus Longus), results showed significant difference between Rigid Tape and KT Tape (p= 0.048). However, there was no significant difference on Tibialis Anterior muscle activation between both tapes while standing. Conclusion: The results indicated that Peroneus longus muscle was more active when applied Rigid Tape rather than KT Tape in ankle instability patients while standing.

Keywords: ankle instability, kinematic, muscle activation, force distribution, Rigid Tape, KT tape

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Authors: S. Alsubari, M. Y. M. Zuhri, S. M. Sapuan, M. R. Ishaks

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Sandwich structures based on cellular cores are increasingly being utilized as energy-absorbing components in the industry. However, determining ideal structural configurations remains challenging. This chapter compares the compression properties of flax fiber-reinforced polylactic acid (PLA) of empty honeycomb core, foam-filled honeycomb and double cell wall square interlocking core sandwich structure under quasi-static compression loading. The square interlocking core is fabricated through a slotting technique, whereas the honeycomb core is made using a corrugated mold that was initially used to create the corrugated core composite profile, which is then cut into corrugated webs and assembled to form the honeycomb core. The sandwich structures are tested at a crosshead displacement rate of 2 mm/min. The experimental results showed that honeycomb outperformed the square interlocking core in terms of their strength capability and SEA by around 14% and 34%, respectively. It is observed that the foam-filled honeycomb collapse in a progressive mode, exhibiting noticeable advantages over the empty honeycomb; this is attributed to the interaction between the honeycomb wall and foam filler. Interestingly, the average SEAs of foam-filled and empty honeycomb cores have no significant difference, around 8.7kJ/kg and 8.2kJ/kg, respectively. In contrast, its strength capability is clearly pronounced, in which the foam-filled core outperforms the empty counterparts by around 33%. Finally, the results for empty and foam-filled cores were significantly superior to aluminum cores published in the literature.

Keywords: compressive strength, flax, honeycomb core, specific energy absorption

Procedia PDF Downloads 58

Authors: Paolo Ragazzi, Olivier Peillon, Paul Fauris, Mathias Simon, Raul Navarro, Juan Carlos Martin, Oriol Casasayas, Laura Pacheco, Albert Perez-Bellmunt

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Introduction: The use of stretching techniques in the sports world is frequent and widely used for its many effects. One of the main benefits is the gain in flexibility, range of motion and facilitation of the sporting performance. Recently the use of Roller-Foam (RF) has spread in sports practice both at elite and recreational level for its benefits being similar to those observed in stretching. The objective of the following study is to compare the results of the Roller-Foam with the proprioceptive neuromuscular facilitation stretching (PNF) (one of the stretchings with more evidence) on the hamstring muscles. Study design: The design of the study is a single-blind, randomized controlled trial and the participants are 40 healthy volunteers. Intervention: The subjects are distributed randomly in one of the following groups; stretching (PNF) intervention group: 4 repetitions of PNF stretching (5seconds of contraction, 5 second of relaxation, 20 second stretch), Roller-Foam intervention group: 2 minutes of Roller-Foam was realized on the hamstring muscles. Main outcome measures: hamstring muscles flexibility was assessed at the beginning, during (30’’ of intervention) and the end of the session by using the Modified Sit and Reach test (MSR). Results: The baseline results data given in both groups are comparable to each other. The PNF group obtained an increase in flexibility of 3,1 cm at 30 seconds (first series) and of 5,1 cm at 2 minutes (the last of all series). The RF group obtained a 0,6 cm difference at 30 seconds and 2,4 cm after 2 minutes of application of roller foam. The results were statistically significant when comparing intragroups but not intergroups. Conclusions: Despite the fact that the use of roller foam is spreading in the sports and rehabilitation field, the results of the present study suggest that the gain of flexibility on the hamstrings is greater if PNF type stretches are used instead of RF. These results may be due to the fact that the use of roller foam intervened more in the fascial tissue, while the stretches intervene more in the myotendinous unit. Future studies are needed, increasing the sample number and diversifying the types of stretching.

Keywords: hamstring muscle, stretching, neuromuscular facilitation stretching, roller foam

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Authors: Evgeny N. Zakharin, Bartosz Majewski

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Foaming polyurethane is a ground improvement technology that is increasingly used for foundation stabilization with differential settlement and controlled foundation structure lifting. This technology differs from conventional mineral grout due to its injection composition, which provides high-pressure expansion quickly due to a chemical reaction. The technology has proven efficient in the typical geological conditions of the United Arab Emirates. An in-situ trial foundation load test has been proposed to objectively assess the deformative and load-bearing characteristics of the soil after injection. The article provides a detailed description of the experiment carried out in field conditions. Based on the practical experiment's results and its finite element modeling, the deformation modulus of the soil after treatment was determined, which was more than five times higher than the initial value.

Keywords: chemical grout, expanding polyurethane resin, foundation remediation, ground improvement

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Authors: Dandi Bachtiar, Mohammed Ausama Abbas, Januar Parlaungan Siregar, Mohd Ruzaimi Bin Mat Rejab

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Short sugar palm fibre and thermoplastic polyurethane were combined to produce new composites by using the extrude method. Two techniques used to prepare a new composite material, firstly, extrusion of the base material with short fibre, secondly hot pressing them. The size of sugar palm fibre was fixed at 250µm. Different weight percent (10 wt%, 20 wt% and 30 wt%) were used in order to optimise preparation process. The optimization of process depended on the characterization mechanical properties such as impact, tensile, and flexural of the new (TPU/SPF) composite material. The results proved that best tensile and impact properties of weight additive fibre applied 10 wt%. There was an increasing trend recorded of flexural properties during increased the fibre loading. Meanwhile, the maximum tensile strength was 14.0 MPa at 10 wt% of the fibre. Moreover, there was no significant effect for additions more than 30 wt% of the fibre.

Keywords: composites, natural fibre, polyurethane, sugar palm

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Authors: Ioan Rusu

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In the operation of power transformers of 110 kV/MV from substations, these are traveled by fault current resulting from MV line damage. Defect electrical contacts are heated when they are travelled from fault currents. In the case of high temperatures when 135 °C is reached, the electrical insulating oil in the vicinity of the electrical faults comes into contact with these contacts releases gases, and activates the electrical protection. To avoid auto-flammability of electro-insulating oil, we designed a security system thermal of electrical contact defects by pouring fire-resistant polyurethane foam, mastic or mortar fire inside a cardboard electro-insulating cylinder. From practical experience, in the exploitation of power transformers of 110 kV/MT in oil electro-insulating were recorded some passing disconnecting commanded by the gas protection at internal defects. In normal operation and in the optimal load, nominal currents do not require thermal secure contacts inside electrical transformers, contacts are made at the fabrication according to the projects or to repair by solder. In the case of external short circuits close to the substation, the contacts inside electrical transformers, even if they are well made in sizes of Rcontact = 10^‑6 Ω, are subjected to short-circuit currents of the order of 10 kA-20 kA which lead to the dissipation of some significant second-order electric powers, 100 W-400 W, on contact. At some internal or external factors which action on electrical contacts, including electrodynamic efforts at short-circuits, these factors could be degraded over time to values in the range of 10^-4 Ω to 10^-5 Ω and if the action time of protection is great, on the order of seconds, power dissipation on electrical contacts achieve high values of 1,0 kW to 40,0 kW. This power leads to strong local heating, hundreds of degrees Celsius and can initiate self-ignition and burning oil in the vicinity of electro-insulating contacts with action the gas relay. Degradation of electrical contacts inside power transformers may not be limited for the duration of their operation. In order to avoid oil burn with gas release near electrical contacts, at short-circuit currents 10 kA-20 kA, we have outlined the following solutions: covering electrical contacts in fireproof materials that would avoid direct burn oil at short circuit and transmission of heat from electrical contact along the conductors with heat dissipation gradually over time, in a large volume of cooling. Flame retardant materials are: polyurethane foam, mastic, cement (concrete). In the normal condition of operation of transformer, insulating of conductors coils is with paper and insulating oil. Ignition points of its two components respectively are approximated: 135 °C heat for oil and 200 ⁰C for paper. In the case of a faulty electrical contact, about 10^-3 Ω, at short-circuit; the temperature can reach for a short time, a value of 300 °C-400 °C, which ignite the paper and also the oil. By burning oil, there are local gases that disconnect the power transformer. Securing thermal electrical contacts inside the transformer, in cardboard tube with polyurethane foams, mastik or cement, ensures avoiding gas release and also gas protection working.

Keywords: power transformer, oil insulatation, electric contacts, Bucholtz relay

Procedia PDF Downloads 133

Authors: W. Sornlar, S. Supothina, A. Wannagon

Abstract:

Lightweight geopolymer can be prepared by using some foaming agents, such as metal powders or hydrogen peroxide; however, it is difficult to control the generated cell size due to the high reactivity of the system. This study aims to investigate the influence of Sodium Lauryl Ether Sulfate (SLES) foam addition and curing temperature on the physical, mechanical, thermal, and microstructure behaviors of the lightweight kaolinite-based geopolymer. To provide porous structure, the geopolymer paste was mixed with 0-15 wt% of SLES foam before casting into the mold. Testing and characterizations were carried out after 28 days. The results showed that SLES foam generated the regular and spherical macropores, which were well distributed in the geopolymer samples. The total porosity increased as SLES foam increased, similarly as the apparent porosity and water absorption. On the other hand, the bulk density and mechanical strength decreased as SLES foam increased. Curing temperature was studied simultaneously due to it strongly affects the mechanical strength of geopolymer. In this study, rising of curing temperature from 27 to 50°C (at 75% relative humidity) improved the compressive strength of samples but deteriorated after curing at 60°C. Among them, the composition of 15 wt% SLES foam (NF15) presented the highest porosity (70.51-72.89%), the lowest density (0.68-0.73 g/cm³), and very low thermal conductivity (0.172-0.197 W/mK). It had the proper compressive strength of 4.21-4.74 MPa that can be applied for the thermal insulation.

Keywords: lightweight, kaolinite-based geopolymer, curing temperature, foaming agent, thermal conductivity

Procedia PDF Downloads 157

Authors: Brahim Safi, Djamila Aboutaleb, Mohammed Saidi, Abdelbaki Benmounah, Fahima Benbrahim

Abstract:

The inorganic wastes are currently used in the manufacture of concretes as mineral additions by cement substitution or as fine/coarse aggregates by replacing traditional aggregates. In this respect, this study aims to valorize the mineral wastes in particular glass wastes to produce granulated foam glass (as fine aggregates). Granulated foam glasses (GFG) were prepared from the glass powder (glass cullet) and foaming agent (limestone) according to applied manufacturing of GFG (at a heat treatment 850 ° C for 20min). After, self-compacting mortars were elaborated with fine aggregate (sand) and other variant mortars with granulated foam glass at volume ratio (0, 30, 50 and 100 %). Rheological characterization tests (fluidity) and physic-mechanical (density, porosity /absorption of water and mechanical tests) were carried out on studied mortars. The results obtained show that a slightly decreasing of compressive strength of mortars having lightness very important for building construction.

Keywords: glass wastes, lightweight aggregate, mortar, fluidity, density, mechanical strength

Procedia PDF Downloads 208

Authors: Ashish Mahalle, Kishore Borakhade

Abstract:

High porosity metal foams are excellent for heat dissipation. There use has been widened to include heat removal from high density microelectronics circuits. Other important applications have been found in compact heat exchangers for airborne equipment, regenerative and dissipative air cooled condenser towers, and compact heat sinks for power electronic. The low relative density, open porosity and high thermal conductivity of the cell edges, large accessible surface area per unit volume, and the ability to mix the cooling fluid make metal foam heat exchangers efficient, compact and light weight. This paper reports the thermal performance of metal foam for high heat dissipation. In experimentation metal foam samples of different pore diameters i.e. 35 µ, 20 µ, 12 µ, are analyzed for varying velocities and heat inputs. The study investigate the effect of various dimensionless no. like Re,Nu, Pr and heat transfer characteristics of basic flow configuration.

Keywords: pores, foam, effective thermal conductivity, permeability

Procedia PDF Downloads 281

Authors: Moez Selmi, Mariem Kacem, Mehrez Jamei, Philippe Dubujet

Abstract:

Earth pressure balance (EPB) tunnel boring machines are designed for digging in different types of soil, especially clay soils. This operation requires the treatment of soil by lubricants to facilitate the procedure of excavation. A possible use of this soil is limited by the effect of treatment on the hydro-mechanical properties of the soil. This work aims to study the effect of a foaming agent on the hydro-mechanical properties of clay soil. The injection of the foam agent in the soil leads to create a soil matrix in which they are incorporated gas bubbles. The state of the foam in the soil is scalable thanks to the degradation of the gas bubbles in the soil.

Keywords: EPB, clay soils, foam agent, hydro-mechanical properties, degradation

Procedia PDF Downloads 342

Authors: P. G. Siddheshwar, B. N. Veena

Abstract:

Rayleigh-B´enard convection of a nanoliquid in shallow, square and tall enclosures is studied using the Khanafer-Vafai-Lightstone single-phase model. The thermophysical properties of water, copper, copper-oxide, alumina, silver and titania at 3000 K under stagnant conditions that are collected from literature are used in calculating thermophysical properties of water-based nanoliquids. Phenomenological laws and mixture theory are used for calculating thermophysical properties. Free-free, rigid-rigid and rigid-free boundary conditions are considered in the study. Intractable Lorenz model for each boundary combination is derived and then reduced to the tractable Ginzburg-Landau model. The amplitude thus obtained is used to quantify the heat transport in terms of Nusselt number. Addition of nanoparticles is shown not to alter the influence of the nature of boundaries on the onset of convection as well as on heat transport. Amongst the three enclosures considered, it is found that tall and shallow enclosures transport maximum and minimum energy respectively. Enhancement of heat transport due to nanoparticles in the three enclosures is found to be in the range 3% - 11%. Comparison of results in the case of rigid-rigid boundaries is made with those of an earlier work and good agreement is found. The study has limitations in the sense that thermophysical properties are calculated by using various quantities modelled for static condition.

Keywords: enclosures, free-free, rigid-rigid, rigid-free boundaries, Ginzburg-Landau model, Lorenz model

Procedia PDF Downloads 219

Authors: Qifei Jing, Vadim V. Silberschmidt, Lin Li, ZhiLi Dong

Abstract:

Graphene oxide (GO) was chemically functionalized to prepare polyurethane (PU) composites with improved mechanical and thermal properties. In order to achieve a well exfoliated and stable GO suspension in an organic solvent (dimethylformamide, DMF), 4, 4′- methylenebis(phenyl isocyanate) and polycaprolactone diol, which were the two monomers for synthesizing PU, were selectively used to functionalize GO. The obtained functionalized GO (FGO) could form homogeneous dispersions in DMF solvent and the PU matrix, as well as provide a good compatibility with the PU matrix. The most efficient improvement of mechanical properties was achieved when 0.4 wt% FGO was added into the PU matrix, showing increases in the tensile stress, elongation at break and toughness by 34.2%, 27.6% and 64.5%, respectively, compared with those of PU. Regarding the thermal stability, PU filled with 1 wt% FGO showed the largest extent of improvement with T2% and T50% (the temperatures at which 2% and 50% weight-loss happened) 16 °C and 21 °C higher than those of PU, respectively. The significant improvement in both mechanical properties and thermal stability of FGO/PU composites should be attributed to the homogeneous dispersion of FGO in the PU matrix and strong interfacial interaction between them.

Keywords: composite, dispersion, graphene oxide, polyurethane

Procedia PDF Downloads 229

Authors: DuckHwan Bae, YongSung Kwon, Min Young Shon, SanTaek Oh, GuNi Kim

Abstract:

The heating behavior of nanometer and micrometer sized Nickel particle-imbedded thermoplastic polyurethane adhesive (TPU) under induction heating is examined in present study. The effects of particle size and content, TPU film thickness on heating behaviors were examined. The correlation between heating behavior and magnetic properties of Nickel particles were also studied. From the results, heat generation increased with increase of Nickel content and film thickness. However, in terms of particle sizes, heat generation of Nickel-imbedded TPU film were in order of 70nm>1µm>20 µm>70 µm and this results can explain by increasing ration of eddy heating to hysteresis heating with increase of particle size.

Keywords: induction heating, thermoplastic polyurethane, nickel, composite, hysteresis loss, eddy current loss, curie temperature

Procedia PDF Downloads 325