• Elastomers and Composites
• /
• v.54 no.1
• /
• pp.54-60
• /
• 2019

The rapid development of the automobile industry is an important factor that led to the dramatic development of synthetic rubber. The tread part of tire that comes in direct contact with the road surface is related to the service life of the tire. Rubber compounds used in tire treads are often blended with SBR (styrene-butadiene rubber) and BR (butadiene rubber) to satisfy physical property requirements. However, when two or more kinds of rubber are blended, phase separation and silica dispersion problems may occur due to non-uniform mixing of the rubber. Therefore, in this study, we synthesized an SBR copolymer with the same composition as that of a typical SBR/BR blend compound by controlling butadiene content during ESBR (emulsion styrene-butadiene rubber) synthesis. Subsequently, silica filled compounds were manufactured using the synthesized ESBR, and their mechanical properties, dynamic viscoelasticity, and crosslinking density were compared with those of the SBR/BR blended compound. When the content of butadiene was increased in the silica filled compound, the cure rate accelerated due to an increased number of allylic positions, which typically exhibit higher reactivity. However, the T-2 compound with increased butadiene content by synthesis less likely to show an increase in crosslink density due to poor silica dispersion. In addition, the T-3 compound containing high cis BR content showed high crosslink density due to its monosulfide crosslinking structure. Because of the phase separation, SBR/BR blend compounds were easily broken and showed similar $M_{100%}$ and $M_{300%}$ values as those of other compounds despite their high crosslink density. However, the developed blend showed excellent abrasion resistance due to the high cis-1,4 butadiene content and low rolling resistance due to the high crosslink density.

• Computers and Concrete
• /
• v.29 no.1
• /
• pp.15-29
• /
• 2022

Concrete-filled steel tubes (CFSTs) are increasingly used as composite sections in structures owing to their excellent load bearing capacity. Therefore, predicting the mechanical behavior of CFST sections under axial compression loading is vital for design purposes. This paper presents the first study on the nonlinear analysis of heated CFSTs with high-strength concrete core containing steel fiber and waste tire rubber under axial compression loading. CFSTs had steel fibers with 0, 1, and 1.5% volume fractions and 0, 5, and 10% rubber particles as sand alternative material. They were subjected to 20, 250, 500, and 750℃ temperatures. Using flow rule and analytical analysis, a model is developed to predict the load bearing capacity of steel tube, and hoop strain-axial strain relationship, and axial stress-volumetric strain relationship of CFSTs. An elastic-plastic analysis method is applied to determine the axial and hoop stresses of the steel tube, considering elastic, yield, and strain hardening stages of steel in its stress-strain curve. The axial stress in the concrete core is determined as the difference between the total experimental axial stress and the axial stress of steel tube obtained from modeling. The results show that steel tube in CFSTs under 750℃ exhibits a higher load bearing contribution compared to those under 20, 250, and 500℃. It is also found that the ratio of load bearing capacity of steel tube at peak point to the load bearing capacity of CFST at peak load is noticeable such that this ratio is in the ranges of 0.21-0.33 and 0.31-0.38 for the CFST specimens with a steel tube thickness of 2 and 3.5 mm, respectively. In addition, after the steel tube yielding, the load bearing capacity of the tube decreases due to the reduction of its axial stiffness and the increase of hoop strain rate, which is in the range of about 20 to 40%.

• Computers and Concrete
• /
• v.31 no.6
• /
• pp.537-543
• /
• 2023

To study the seismic behavior of recycled aggregate concrete filled circular steel tube (RACFCST) frames, the seismic behavior experiment of RACFCST frame was carried out to measure the hysteresis curve, skeleton curve and other seismic behavior indexes. Moreover, based on the experimental study, a feasible numerical analysis model was established to analyze the finite element parameters of 8 RACFCST frame specimens, and the influence of different variation parameters on the seismic behavior index for RACFCST frame was revealed. The results showed that the skeleton curve of specimens under different axial compression ratios were divided into three stages: elastic stage, elastic-plastic stage and descending stage, and the descending stage was relatively stable, indicating that the specimen had stronger deformation capacity in the descending stage. With the increase of axial compression ratio, the peak bearing capacity of all specimens reduced gradually, and the reduction was less than 5%. With the decrease of beam-column linear stiffness ratio, the peak bearing capacity decreased gradually. With the decrease of yield bending moment ratio of beam-column, the peak bearing capacity decreased gradually, and the decreasing rate of peak bearing capacity gradually accelerated. In addition, compared with the axial compression ratio, the beam-column linear stiffness ratio and the yield bending moment ratio of beam-column had a more significant influence on the peak bearing capacity of RACFCST frame.

• Journal of the Korean Ceramic Society
• /
• v.45 no.11
• /
• pp.750-754
• /
• 2008

The artificial aggregates with dense surface layer (shell) was fabricated and the dependence of water emission rate upon the shell structures was studied. The EAF dust containing many flux components and waste white clay with ignition loss of above 48% were used as for liquid phase and gas forming agents during a sintering process respectively. In addition, the shell structure was modified with various processes and the modification effect on water emission rate was analyzed. The pores under $10{\mu}m$ were found in the sintered artificial light aggregates and disappeared by incorporating to a bigger pore during re-sintering. The water emission rate in an initial step depended on a void content of aggregates filled in a bottle rather than a shell structure. But, after 7 days where the water emission of the aggregate with a shell is above 40%, the shell of aggregates suppressed the water emission. The core of aggregates was exposed and most shell was lost when crushed to smaller size so, the ability for suppressing water emission of the crushed aggregates decreased. The activation energy for the water emission was $3.46{\pm}0.25{\times}10^{-1}$J/mol for the most specimens showing that the activation energy is irrelevant to the pore size distribution and shell structure.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.4 no.2
• /
• pp.47-54
• /
• 1971

The difference in growth rate of p. orientalis cultured on muddy bottom region and sandy bottom region in a pond filled with sea water were studied. For the investigation of the growth rate, the body length and the body weight were determined. Five individuals from each experimental region were sampled in random. The samples were collected at ten-day intervals. The survival rate, the qredator of p. orientalis, and the water conditions during the experimental period were also determined. The results in this study are summerized as follows: 1. The growth rate of p. orientalis which was cultured in the muddy bottom region was greater than that in the sandy bottom region. This is attributable in either case regardless of whether they were cultured with or without food, 2. The relationship between the culturing period (X) and the body length (Y) is : Muddy bottom, Food Y=0.58497X+25.05210 Sandy bottom, Food Y=0.51030X+26.57900 Muddy bottom, No food Y=0.22352X+32.79360 Sandy bottom, No food Y=0.l1418X+31.20740 3. The relationship between the culturing period (X) and the body weight (Y) is : Muddy bottom, Food Y=0.09062X-2.11140 Sandy bottom, Food Y=0.06992X-1.19640 Muddy bottom, No food Y=0.01615X+0.51150 Sandy bottom, No food Y=0.00495X+0.56150 4. When the predator is not present, $84\%$ of P. orientalis may survive. 5. Acanthogobius flavimanus is one of the predator of P. orientalis. 6. It is considered that the variation of water conditions of the pond, in which water had been exchanged 12 times per month, did not affect to the survival rate of P. orientalis.

• Carbon letters
• /
• v.7 no.2
• /
• pp.87-96
• /
• 2006

This paper describes the physical properties of filled Nylon6 composites resin with nano-sized carbon black particle and graphite nanofibers prepared by melt extrusion method. In improving adhesions between resin and fillers, the surface of the carbon filler materials were chemically modified by thermo-oxidative treatments and followed by treatments of silane coupling agent. Crystallization temperature and rate of crystallization increased with increases in filler concentration which would act as nuclei for crystallization. The silane treatments on the filler materials showed effect of reduction in crystallization temperature, possibly from enhancement in wetting property of the surface of the filler materials. Percolation transition phenomenon at which the volume resistivity was sharply decreased was observed above 9 wt% of carbon black and above 6 wt% of graphite nanofiber. The graphite nanofibers contributed to more effectively in an increase in electrical conductivity than carbon black did, on the other hand, the silane coupling agent negatively affected to the electrical conductivity due to the insulating property of the silane. Positive temperature coefficient (PTC) phenomenon, was observed as usual in other composites, that is, temperature increase results conductivity increase. The dispersity of the fillers were excellently approached by melt extrusion of co-rotational twin screw type and it could be illustrated by X-ray diffraction and SEM.

• Elastomers and Composites
• /
• v.36 no.1
• /
• pp.37-43
• /
• 2001

Influence of the filler composition ratio on cure characteristics and bound rubber content of the compounds and on physical properties of the vulcanizates were studied using both silica and carbon black-filled styrene-butadiene rubber (SBR) compounds with the total filler content of 80.0 phr. The bound rubber content increased slightly with increase of the silica content ratio. The viscosity also increased with increasing the silica content ratio, especially increased steeply after the silica content of 60.0 phr. The cure times obtained with a rheometer, t2, t40, and t90, are increased by increasing the silica content ratio and the cure rate decreased. The delta torque increased with the increased silica content ratio. Variation or the modulus with the silica content ratio showed a decreased trend though the delta torque increased. The tan ${\delta}$ at $60^{\circ}C$ decreased with increased of the silica content ratio.

• Korean Journal of Materials Research
• /
• v.21 no.4
• /
• pp.196-201
• /
• 2011

It is known that the relative dielectric constant of insulating polyethylene matrix composites with conducting materials (such as carbon black and metal powder) increases as the conducting material content increases below the percolation threshold. Below the percolation threshold, dielectric properties show an ohmic behavior and their value is almost the same as that of the matrix. The change is very small, but its origin is not clear. In this paper, the dielectric properties of carbon black-filled polyethylene matrix composites are studied based on the effect medium approximation theory. Although there is a significant amount of literature on the calculation based on the theory of changing the parameters, an overall discussion taking into account the theory is required in order to explain the dielectric properties of the composites. Changes of dielectric properties and the temperature dependence of dielectric properties of the composites made of carbon particle and polyethylene below the percolation threshold for the volume fraction of carbon black have been discussed based on the theory. Above the percolation threshold, the composites are satisfied with the universal law of conductivity, whereas below the percolation threshold, they give the critical exponent of s = 1 for dielectric constant. The rate at which the percentages of both the dielectric constant and the dielectric loss factor for temperature increases with more volume fraction below the percolation threshold.

• Proceedings of the KIPE Conference
• /
• 2010.07a
• /
• pp.246-247
• /
• 2010

This paper deals with the water treatment of the leachate from sewage filled ground by a pulsed power technology. Leachate from sewage filled ground should be treated below regulation level of COD in order to prevent environmental pollution and usually treated by a chemical method. Among the pollutants mixed in the leachate, chemical compounds of benzene series are known to be difficult to break down, and need to use high cost treat methods. The treatment of the benzene compounds by high power pulsed power supply was studied. For the high-rate, cost-effective treatment of leachate, pulsed power supply should have high repetition rates and require switching devices of long lifetime. In order to meet the demands of the above condition, pulsed power generator based on semiconductor switches using IGBTs as primary switches were developed. The experimental results verified that benzene compounds can be treated effectively by high voltage electric pulses, and this fact indicates that the treatment method by pulsed power source is a promising substitute.

• Korea-Australia Rheology Journal
• /
• v.21 no.3
• /
• pp.193-200
• /
• 2009

We present a direct simulation technique for two-dimensional mold-filling simulations of fluids filled with a large number of circular disk-like rigid particles. It is a direct simulation in that the hydrodynamic interaction between particles and fluid is fully considered. We employ a pseudo-concentration method for the evolution of the flow front and the DLM (distributed Lagrangian multipliers)-like fictitious domain method for the implicit treatment of the hydrodynamic interaction. Both methods allow the use of a fixed regular discretization during the entire computation. The discontinuous Galerkin method has been used to solve the concentration evolution equation and the rigid-ring description has been introduced for freely suspended particles. A buffer zone, the gate region of a finite area subject to the uniform velocity profile, has been introduced to put discrete particles into the computational domain avoiding any artificial discontinuity. From example problems of 450 particles, we investigated the particle motion and effects of particles on the flow for both Newtonian and shear-thinning fluid media. We report the prolonged particle movement toward the wall in case of a shear-thinning fluid, which has been interpreted with the shear rate distribution.