• Elastomers and Composites
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• v.36 no.1
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• pp.44-51
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• 2001

To see the effect of chemical surface modification, the carbon black surfaces were treated with three types of chemicals (KOH, $H_3PO_4$, and benzene). Vulcanization and mechanical properties of a styrene-butadiene rubber (SBR) were investigated depending on the chemical treatments. The surface free energy increased considerably with the treatments by both the acid (HCB) and base (KCB), but only a slight increase was observed for benzene treatment(BCB). The BCB showed the highest level of the London dispersive component. The vulcanization reaction was found to be faster in the order of KCB-SBR> BCB-SBR> VCB-SBR(virgin) > HCB-SBR. The difference in minimum and maximum torque of rheocurve, representing the degree of crosslinking, was found to be higher for the BCB-SBR compared to those of VCB-SBR, KCB-SBR, and HCB-SBR. The BCB-SBR and KCB-SBR showed the improved tensile and dynamic mechanical properties. A linear relationship was found to exist between the London dispersive component of surface free energy and mechanical properties.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.3
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• pp.97-103
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• 2023

Barrier films for transparent packaging materials with excellent moisture barrier properties are prepared, utilizing a nanoclay dispersion coating layer formed after a pretreatment process of plasma activation surface treatment process under vacuum at room temperature. Attention is paid on optimizing the coupling additive through the appropriate crosslinking process and optimal dispersion process of the coating process to enhance adhesion. Analysis of the functional coating thin film shows that the water vapor transmission rate is less than 10 g/m²/24 hrs (ASTM F-1249) and the oxygen transmission rate is less than 30 cc/m²/24 hrs (ASTM D3985). It is shown that water barrier properties of coating thin film prepared in this study are greater than conventional untreated films by 10 times or more. The thickness of the transparent gas barrier film is within 0.1 mm, and the transparent gas barrier complex is implemented in two layers. In the study of PET thin film interface characteristics, FT-IR experimental analysis shows the reaction activity was optimized at RDS 1.125 %.

• Macromolecular Research
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• v.17 no.10
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• pp.776-784
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• 2009

N,N-dimethyldodecylamine (tertiary amine)-modified MMT (DDA-MMT) was prepared as an organically modified layered silicate (OLS), after which styrene-butadiene rubber (SBR) nanocomposites reinforced with the OLS were manufactured via the latex method. The layer distance of the OLS and the morphology of the nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). By increasing the amount of N,N-dimethyldodecylamine (DDA) up to 2.5 g, the maximum values of torque, tensile strength and wear resistance of the SBR nanocomposites were increased due to the increased dispersion of the silicate layers in the rubber matrix and the increased crosslinking of the SBR nanocomposites by DDA itself. When SBR nanocomposites were manufactured by using the ternary filler system (carbon black/silica/OLS) to improve their dynamic properties as a tire tread compound, the tan $\delta$(at $0^{\circ}C$ and $60^{\circ}C$) property of the compounds was improved by using metal stearates instead of stearic acid. The mechanical properties and wear resistance were increased by direct substitution of calcium stearate for stearic acid because the filler-rubber interaction was increased by the strong ionic effect between the calcium cation and silicates with anionic surface. However, as the amount of calcium stearate was further increased above 0.5 phr, the mechanical properties and wear resistance were degraded due to the lubrication effect of the excessive amount of calcium stearate. Consequently, the SBR/organoclay nanocomposites that used carbon black, silica, and organoclay as their ternary filler system showed excellent dynamic properties, mechanical properties and wear resistance as a tire tread compound for passenger cars when 0.5 phr of calcium stearate was substituted for the conventionally used stearic acid.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.3
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• pp.135-141
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• 2010

Researchers continue to explore possibilities for expanding additive manufacturing (AM) technologies into direct product manufacturing. One limitation is in the materials available for use in AM that can meet the needs of end-use applications. Stereolithography (SL) is an AM technology well known for its precision and high quality surface finish capabilities. SL builds parts by selectively crosslinking or solidifying photo-curable liquid resins, and the resin industry has been continuously developing new resins with improved performance characteristics. This paper introduces a unique SL machine that can fabricate parts out of multiple SL materials. The technology is based on using multiple vats positioned on a rotating vat carousel that contain different photo-curable materials. To change the material during the process, the build platform is raised out of the current vat, a new vat with a different material is rotated under the platform, and the platform is submerged into the new vat so that the new material can be used. This paper introduces a new vat exchange mechanism, cleaning process, recoating process, resin leveling mechanism and process planning technologies for the implementation of multiple material SL. An overview of the system framework is provided and the system integration and control software is described. In addition, several multiple material test parts are designed, fabricated, and described.

• Korean Journal of Materials Research
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• v.5 no.8
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• pp.966-978
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• 1995

Amidoximated composite fiber adsorbents were prepared for separation of uranium from seawater and characterized by various instrumental techniques, such as IR spectroscopy, CHN elemetal analyzer and SEM. The swelling ratios and yields of the AN-TEGMA and AN-TEGMA-DVB copolymers were decreased with an increase in crosslinklng agents, such as DVB and TEGMA composition. The yield of 85-92% and 82-88% of AN-TEGMA and AN-TEGMA-DVB copolymers respectively were found. The porosity was also decreased with increase in crosslinking compositions, and it was found that the AN-TEGMA-DVB porosity copolymers were smaller than the value of AN-TEGMA copolymer. We investigated that the adsorbent with the composite fiber adsorbents were well dispersed on the surface of Its by SEM. The optimum contents of containing adsorbent in the copolymer was 40 weight percent. The capacity of uraniyl ion through the composite fiber adsorbent containing the amidoxime group was miximized a pH level of 8. Also, if was found that the synthesized composite fiber adsorbent was good material, due to a pH level of 8.3 of seawater, for separation of uraniyl ion from seawater.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.57-63
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• 2017

In this study, we identified how the water content change in various NCO index affects the static comfort of polyurethane seat foam pad for automobiles. In order to identify factors that affect the static comfort, a static load test was performed using UTM to plot a hysteresis curve. The hardness of the foam when it was modified by 25, 65%, hysteresis loop area, hysteresis loss (%), and Sag factor were also obtained. By measuring the swelling ratio, it was confirmed that, as the water content increased in a fixed NCO index, the hardness and crosslinking density increased while the restoring force decreased due to the increase of urea bond. Also the Sag factor decreased due to the increase of surface hardness. As the NCO index increased in a fixed water content, the urethane and urea bond reacted more with isocyanate, leading to an increase in hardness and decrease in restoring force.

• Polymer(Korea)
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• v.39 no.2
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• pp.240-246
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• 2015

Formation of a strong 3-dimensional interfacial network structure via chemical reaction between hydroxyl group on silica surface and NR chain by the addition of bis(triethoxysilylpropyl)tetrasulfide (TESPT) into silica-filled NR compound was observed by using Py-GC/MS and SEM. Addition of TESPT into silica-filled NR compound decreased scorch time ($t_{10}$) due to increased sulfur content, and reduced cure rate index (CRI) via continuous reaction between sulfur atoms in TESPT, which acted as a sulfur donor, and activators and/or accelerators. Addition of TESPT in the compound improved processability and mechanical properties of the compound. Overall, we observed that the addition of TESPT into the silica-filled NR compound formed a silica-TESPT-NR network, and thus the degree of crosslinking was increased resulting in improved mechanical properties.

• Journal of Adhesion and Interface
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• v.18 no.2
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• pp.53-58
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• 2017

In this study, to overcome a complicated shoe adhesion process such as buffing, pre-treatment by primer in the rubber component of the shoe, we studied adhesion and mechanical properties with rubber compound added $MgCl_2$. We determined adhesion properties of $MgCl_2$ content. Especially, the rubber containing $MgCl_2$ exhibited good adhesion properties to water-based adhesion. Since $MgCl_2$ is a water-soluble salt, it was judged that this phenomenon occurred. The results are confirmed by contact angle and surface morphology measurement. In addition, in the case of rubber compound added $MgCl_2$, the crosslinking efficiency was increased and the NBS resistance was increased.

• Polymer(Korea)
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• v.29 no.1
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• pp.1-7
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• 2005

Interpenetrating polymer network (PN) is a mixture of network polymers. The characteristics of IPN material is the control of morphology during the IPN synthesis. By controlling the relative kinetics of chemical reaction (as well as gellation) and phase separation, the morphology of IPN can be controlled to obtain materials with nano-scale domain and also the co-continuous phase. Other important advantage is the fact that the morphology is permanent due to the presence of the physical interlocking between the networks. The combination of hydrophilic polyurethane and hydrophobic polystyrene in IPN form provides enhanced blood compatibility due to the co-existence of the hydrophilic and hydrophobic domains in nano-scale on the surface. The reaction temperature, reaction pressure and the degree of crosslinking were varied during the IPN synthesis and the morphology and blood compatibility of the resulting IPN materials were studied.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.5
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• pp.36-42
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• 2019

In this study, the pre-treatment of lyocell fabrics was performed using phosphoric acid (PA) as a phosphorus flame retardant and melamine resin (MR) as a cross-linking agent to fabricate carbon fabrics using lyocell fibers. The physical and chemical changes were investigated by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD) and weight analysis. We confirmed that the weight yield of the carbon fabrics compared to the untreated fabrics increased by 14.7%, and width and length yield of the fabrics increased by 15% and 15.5%, respectively. This may be due to the effect of promoting the dehydration reaction of cellulose, forming char on the fiber surface, which induces a crosslinking reaction in the cellulose molecule and stabilizes the structure upon pyrolysis.