• Journal of the Korean Geosynthetics Society
• /
• v.22 no.3
• /
• pp.37-46
• /
• 2023

In this paper, the physical properties, stress deformation and strength characteristics, density and permeability characteristics of silty sand (SM) by fines content were analyzed through indoor tests. also based on the results of the indoor tests, a compact analysis was performed according to the content of SM, and the applicability of SM ground to the compacted target layer was evaluated by comparing it with the measurement data of the actual problem site. As a result of indoor tests and compression analysis, SM changed its mechanical properties from sandy soil to viscous soil when the fine particle content was 35% or higher, and using field measurement data, SM was found to have a higher compression tendency than direct subsidence. Therefore, the mechanical characteristics of SM above Fc 35% are considered to be similar to that of viscous soil, which is different from the compression characteristics of the tendency of immediate subsidence to conventional sandy soil, so it is necessary to present the mechanical characteristics of SM through further research. The research findings highlight the importance of considering consolidation settlement in silty sand (SM) when evaluating soft soil conditions. These findings can aid in revising criteria for assessing weak ground conditions by providing essential engineering property data based on varying fines content in silty sand.

• Applied Chemistry for Engineering
• /
• v.27 no.6
• /
• pp.612-619
• /
• 2016

In this research, an alumino-borosilicate foamed glass with sound absorption property was prepared using the waste borosilicate glass obtained from the recycling process of waste liquid crystal display (LCD) panel. A 100 g of pulverized waste borosilicate glass with the particle size of under 325 mesh, was mixed with 0.3 g (wt/wt) of graphite, each 1.5 g (wt/wt) of $Na_2CO_3$, $Na_2SO_4$ and $CaCO_3$ as a foaming agent, and 6.0 g (wt/wt) of $H_3BO_3$ and 3.0 g (wt/wt) of $Al_2O_3$ as a pore control agent. Following mixture was under the foaming process for 20 minutes at a foaming temperature of $950^{\circ}C$. The result yielded the foaming agent with 45% of the opened porosity and 0.5-0.7 of the sound absorbing coefficient. This alumino-borosilicate foamed glass with the sound absorption property showed excellent physical and mechanical properties such as density of $0.21g/cm^3$, bending strength of $55N/cm^2$ and compression strength of $298N/cm^2$ which can be ideally used as sound absorption materials with heat-resisting and chemical-resisting property.

• Polymer(Korea)
• /
• v.39 no.1
• /
• pp.64-70
• /
• 2015

Thermally expandable microcapsules (TEMs) can be expanded upon heating since the activation energy of liquid hydrocarbon at the core of the TEMs increased at high temperature. Due to this property, TEMs are widely used in the industry as blowing agents or light-weight fillers. In this article, chemical blowing agent and TEM were used for making polypropylene (PP) foams, and their mechanical properties were compared. Physical properties (tensile strength, impact strength etc.) of PP foams decreased with increasing the amount of blowing agents while weight of specimen decreased. However, PP foam produced with TEMs showed higher impact strength than the one with a chemical blowing agent. In order to figure out the difference of impact strength, the morphology of PP foamed was investigated. Expanding properties of TEM can be controlled by changing core back distance.

• Journal of the Korean Society for Precision Engineering
• /
• v.3 no.1
• /
• pp.40-49
• /
• 1986

Crack, craze and void are common defects which may be found in the bulk of polymeric materials such as either themoplastics or thermosets. The healing phenomena, autohesion, of these defects are known to be a intrinsic material property of various polymeric materials. However, only a few experimental and theoretical investigations on crack, void and craze healing phenomena for various polymeric materials have been reported up to date [1, 2, 3]. This may be partly due to the complications of healing processes and lacking of appropriate theoretical developments. Recently, some investigators have been urged to study the healing phenomena of various polymenic materials since the significance of the use of polymer based alloys or composites has been raised in terms of specific strength and energy saving. In the earlier published reports [1, 2, 3, 4], the crack and void healing velocity, healing toughness and some other healing mechanical and physical properties were measured experimentally and compared with predicted values by utilizing a simple model such as the reptation model under some resonable assumptions. It seems, however, that the general acceptance of the proposed modeling analyses is yet open question. The crack healing processes seem to be complicate and highly dependent on the state of virgin material in terms of mechanical and physical properties. Furthermore, it is also strongly dependent on the histories of crack, craze and void development including fracture suface morphology, the shape of void and the degree of disentanglement of fibril in the craze. The rate of crack healing may be a function of environmental factors such as healing temperature, time and pressure which gives different contact configurations between two separated surfaces. It seems to be reasonable to assume that the crack healing processes may be divided in several distinguished steps like stress relaxation with molecular chain arrangement, surface contact (wetting), inter- diffusion process and com;oete healing (to obtain the original strength). In this context, it is likely that we no longer have to accept the limitation of cumulative damage theories and fatigue life if it is probable to remove the defects such as crack, craze and void and to restore the original strength of polymers or polymer based compowites by suitable choice of healing histories and methods. In this paper, we wish to present a very simple and intuitive theoretical model for the prediction of healed fracture toughness of cracked or defective polymeric components. The central idea of this investigation, thus, may be the modeling of behavior of chain molecules under healing conditions including the effects of chain scission on the healing processes. The validity of this proposed model will be studied by making comparisons between theoretically predicted values and experimentally determined results in near future and will be reported elsewhere.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.30 no.1
• /
• pp.63-72
• /
• 2024

Poly (butylene adipate-co-terephthalate) (PBAT) is one of the representative biodegradable polymers with high ductility and processability to replace petroleum-based polymers. Many investigations have been conducted to broaden the applications of PBAT in a variety of industries, including the food packaging, agricultural mulching film, and logistics and distribution fields. Foaming process is widely known technique to generate the cell structure within the polymer matrix, offering the insulation and light weight properties. However, there was no commercially feasible foam product based on biodegradable polymers, especially PBAT, and maintaining a proper melt viscosity of the polymer would be a key parameter for the foaming process. In this study, chemical foaming agent and cross-linking agent were introduced to PBAT, and a compression molding process was applied to prepare a foam sheet. The correlation between cell morphological structures and mechanical and physical properties was evaluated. It was found that PBAT with foam structures effectively reduced the density and thermal conductivity, allowing them to be suitable for applications such as insulation and lightweight packaging or cushion materials.

• Membrane Journal
• /
• v.26 no.4
• /
• pp.239-252
• /
• 2016

Two-dimensional materials offer unique characteristics for membrane applications to water technology. With its atomic thickness, availability and stackability, graphene in particular is attracting attention in the research and industrial communities. Here, we present a brief overview of the recent research activities in this rising topic with bringing two membrane architecture into focus. Pristine graphene in single- and polycrystallinity poses a unique diffusion barrier property for most of chemical species at broad ambient conditions. If well designed and controlled, physical and chemical perforation can turn this barrier layer to a thinnest feasible membrane that permits ultimate permeation at given pore sizes. For subcontinuum pores, both molecular dynamics simulations and experiments predict potential salt rejection to envisage a seawater desalination application. Another novel membrane architecture is a stack of individual layers of 2D materials. When graphene-based platelets are chemically modified and stacked, the interplanar spacing forms a narrow transport pathway capable of separation of solvated ions from pure water. Bearing unbeknownst permeance and selectivity, both membrane architecture - ultrathin porous graphene and stacked platelets - offer a promising prospect for new extraordinary membranes for water technology applications.

• Investigative Magnetic Resonance Imaging
• /
• v.11 no.1
• /
• pp.10-19
• /
• 2007

Conventional MRI methods using T1-, T2-, diffusion-, perfusion-weighting, and functional imaging rely on characterizing the physical and functional properties of the tissue. In this review, we introduce an imaging modality based on measured the mechanical properties of soft tissue, namely magnetic resonance elastography (MRE). The use of palpation to identify the stiffness of tissue remains a fundamental diagnostic tool. MRE can quantify the stiffness of the tissue thereby providing a objective means to measure the mechanical properties. To accomplish a successful clinical setting using MRE, hardware and software techniques in the area of transducer, pulse sequence, and imaging processing algorithm need to be developed. Transducer, a mechanical vibrator, is the core of MRE application to make wave propagate invivo. For this reason, considerations of the frame of human body, pressure and friction of the interface, and high magnetic field of a MRI system needs to be taken into account when designing a transducer. Given that the wave propagates through human body effectively, developing an appropriate pulse sequence is another important issue in obtaining an optimal image. In this review paper, we introduce the technical aspects needed for MRE experiments and introduce several applications of this new field.

• Carbon letters
• /
• v.11 no.4
• /
• pp.279-284
• /
• 2010

Graphene is one of the most promising materials for many applications. It can be used in a variety of applications not only as a reinforcement material for polymer to obtain a combination of desirable mechanical, electrical, thermal, and barrier properties in the resulting nanocomposite but also as a component in energy storage, fuel cells, solar cells, sensors, and batteries. Recent research at Michigan State University has shown that it is possible to exfoliate natural graphite into graphite nanoplatelets composed entirely of stacks of graphene. The size of the platelets can be controlled from less than 10 nm in thickness and diameters of any size from sub-micron to 15 microns or greater. In this study we have investigated the influence of melt compounding processing on the physical properties of a polyamide 6 (PA6) nanocomposite reinforced with exfoliated graphite nanoplatelets (xGnP). The morphology, electrical conductivity, and mechanical properties of xGnP-PA6 nanocomposite were characterized with electrical microscopy, X-ray diffraction, AC impedance, and mechanical properties. It was found that counter rotation (CNR) twins crew processed xGnP/PA6 nanocomposite had similar mechanical properties with co-rotation (CoR) twin screw processed or with CoR conducted with a screw design modified for nanoparticles (MCoR). Microscopy showed that the CNR processed nanocomposite had better xGnP dispersion than the (CoR) twin screw processed and modified screw (MCoR) processed ones. It was also found that the CNR processed nanocomposite at a given xGnP content showed the lowest graphite X-ray diffraction peak at $26.5^{\circ}$ indicating better xGnP dispersion in the nanocomposite. In addition, it was also found that the electrical conductivity of the CNR processed 12 wt.% xGnP-PA6 nanocomposite is more than ten times higher than the CoR and MCoR processed ones. These results indicate that better dispersion of an xGnP-PA6 nanocomposite is attainable in CNR twins crew processing than conventional CoR processing.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.8 no.4
• /
• pp.93-99
• /
• 2000

Treatment of shaving scrap, a chrome containing solid scrap generated by leather manufacturing process, has been so far depended on mainly incineration, soil landfill and ocean dumping, which give bad impact on environment and cause pollution. Shaving scrap generates from the mechanical work for controlling the final thickness of leather and its main components are collagen protein and pan of chromium compound. For the purpose of reusing this leather waste as resources, researches in connection with collagen fiber recovery, gelable protein recovery and liquid fertilizer is being speedily progressed. In the experiment, shaving scrap went through wet pulverizing treatment by physical and chemical methods. Then, making the leather sheet evenly, it is mixed with natural latex and every kind of binding materials in the container, and the mixtures were passed through experimental hydraulic press machine and applied to Fourdrinier machine respectively. Lastly, a test for fading out physical strength and properties of multiple-purpose of leather-like material was performed on a continuous leather sheet prepared by the experiment. In result, the physical strength and properties of leather-like material showed noticeable differences according to mixing ratio of binding materials, beating methods and the Ends of binding materials selected, and generally tear strength was the weakest property among others. Also, by the pilot scale experiment in sequence, it was possible to manufacture recycled goods made of soft and hard types of leather-like material with various performances.

• Polymer(Korea)
• /
• v.34 no.6
• /
• pp.522-526
• /
• 2010

Bacterial cellulose is produced by the bacterium Gluconacetobacter xylinus, which forms a nanofibrous pellicle in its culture medium. We studied properties of the bacterial cellulose such as crystallinity, viscosity, morphology, and mechanical properties according to the carbon source. Static cultures of Gluconacetobacter sp. V6 were performed in three kinds of media: standard Hestrin-Schramm medium, and modified medium with either glycerol or molasses as carbon sources. Cell growth and cellulose yield were increased in the glycerol and molasses media. The culture in the glycerol medium improved the physical properties of cellulose such as crystallinity, intrinsic viscosity, and breaking stress. However, the culture in the molasses medium decreased crystallinity, crystallite size, and intrinsic viscosity of cellulose. In summary, the cellulose yield was remarkably improved in the molasses medium, but with inferior structural properties.