• Polymer(Korea)
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• v.27 no.1
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• pp.40-45
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• 2003

In this work, the effect of different contents of $Fe_3O_4$ and temperature variation on the electrical conductivity ($\sigma$) in the polar acrylonitrile butadiene rubber (NBR)/$Fe_3O_4$ (magnetite) mixture system was investigated. It was found that the percolation threshold concept holds true for the conductive particle-filled composites where $\sigma$ indicates a nearly sharp increase when the concentration of magnetite in the mixture exceeds 22%. The temperature dependence of $\sigma$ was thermally activated below and at the percolation threshold ($P_c$). Magnetite acted as reinforcing and conductive filler for NBR. At room temperature and higher voltages, the electrical current was proportional to the square of voltage ($I{\propto}V^2$) for the composites which contain 30 phr of magnetite. Moreover, it was shown that the composites with magnetite of 50 phr showed the highest tensile strength and elongation at break, which was due to the formation of optimal physical interlock and crosslinking. The results of 100%, 200%, and 300% Young moduli said that the moduli are largely correlated with reinforcement effect of magnetite and viscosity of the blends from torque curve.

• Elastomers and Composites
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• v.42 no.1
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• pp.9-19
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• 2007

In this study, SBR (Styrene-butadiene rubber: solid content: 25 wt%) nanocomposites reinforced with carbon/organoclay(C18-MMT) were manufactured by a latex method. The SBR nanocomposites was made with the dual phase fillers. The mixing ratios, i.e. carbon black/C18-MMT, were 50/0, 49/1, 48/2, 47/3, 45/5, 44/6, 40/10. Total filler content of compounds was restricted to 50 phr. Cure characteristics and mechanical properties of SBR nanocomposites with carbon black and C18-MMT were evaluated. The SBR nanocomposites containing 49/1 ratio of carbon black/C18-MMT showed good dispersity and excellent values of ODR torque, tensile strength, modulus and tear energy. It was found that the improvement of the mechanical properties was mainly due to the reinforcing effect, i.e., the improvement of dispersion of silicates in the rubber matrix.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.3
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• pp.181-185
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• 2020

Hazardous and noxious substance (HNS) detection sensors were fabricated using multi-walled carbon nanotubes (MWCNTs) and various binder materials for ion batteries. To obtain uniformly printed films, the printing precision according to the substrate cleaning method was monitored, and the printing paste mixing ratio was investigated. Binders were prepared using styrene butadiene rubber + carboxymethyl cellulose (SBR+CMC), polyvinylidene fluoride + n-methyl-2-pyrrolidene (PVDF+NMP), and mixed with MWCNTs. The surface morphology of the printed films was examined using an optical microscope and a scanning electron microscope, and their electrical properties are investigated using an I-V sourcemeter. Finally, sensing properties of MWCNT printed films were measured according to changes in the concentration of the chemical under the various applied voltages. In conclusion, the MWCNT printed films made of (SBR+CMC) were found to be feasible for application to the detection of hazardous and noxious chemicals spilled in seawater.

• Resources Recycling
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• v.22 no.6
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• pp.33-40
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• 2013

Due to the environmental problem caused by plastics largely used in various fields, the importance of recycling is being emphasized. A research on material separation of ABS and PS mixed plastic waste, using a triboelectrostatic separator, was carried out for recovery the ABS. As a results of research on charging characteristic for choosing charging material, it was confirmed that ABS was optimum charging material for a tribo-charger in the material separation of ABS and PS. In the material separation using ABS charger, ABS grade of 99.5% and recovery of 92.5% were achieved at 20 kV, splitter position +2 cm from the center and 30% relative humidity. Therefore, material separation technique for recycling ABS and PS mixed plastic waste was established.

• Polymer(Korea)
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• v.37 no.6
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• pp.764-769
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• 2013

Starch was grafted by poly(methyl methacrylate) through the emulsion polymerization method. Modified starch/(acrylonitrile-butadiene rubber) (NBR) compounds were prepared by a latex blend method. The morphology, thermal properties and mechanical properties of the modified starch/carbon black/NBR composites were investigated with the change of starch concentration. The mechanical properties of the composites were improved by the addition of modified starch. But, when the concentration of modified starch was higher than 40 phr, the mechanical properties were deteriorated due to the poor dispersion of modified starch. At the same ratio of starch to carbon black, the composite showed a synergistic reinforcing effect by the good dispersion and high cross-linking density. In addition, the tensile strength, storage modulus, hardness, swelling and other properties were the best.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.4
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• pp.16-24
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• 2012

To characterize the coating structure, diverse methods such as mercury intrusion, nitrogen adsorption and oil absorption methods have been developed and widely employed. These indirect techniques, however, have some limitation to explain the actual coating structure. Recently microscopic observation methods have been tried for analyzing structural characteristics of coating layers. Preparation of the undamaged cross section of a coating layer is essential for obtaining high quality image for analysis. In this study, distortion-free cross-section of the coating layer was prepared using a grinding and polishing technique. The coated paper was embedded in epoxy resin and cured. After curing the resin block it was ground with abrasive papers and then polished with diamond particle suspension and nylon cloth. Polished coating layer was sufficient enough to obtain undamaged cross sectional images with scanning electron microscope under backscattered electron image mode. In addition, the SEM images allowed distinction of the coating layer components. Also S/B latex film formed between pigment particles was visualized by osmium tetroxide staining. Pore size distribution and pore orientation were evaluated by image analysis from SEM cross-sectional images.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.28 no.3
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• pp.241-256
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• 2018

Objectives: This study aimed to review the characteristics of three-dimensional printing technology focusing on printing types, materials, and health hazards. We discussed the methodologies for exposure assessment on hazardous substances emitted from 3D printing through article reviews. Methods: Previous researches on 3D printing technology and exposure assessment were collected through a literature review of public reports and research articles reported up to July 2018. We mainly focused on introducing the technologies, printing materials, hazardous emissions during 3D printing, and the methodologies for evaluation. Results: 3D printing technologies can be categorized by laminating type. Fused deposition modeling(FDM) is the most widely used, and most studies have conducted exposure assessment using this type. The printing materials involved were diverse, including plastic polymer, metal, resin, and more. In the FDM types, the most commonly used material was polymers, such as acrylonitrile-butadiene-styrene(ABS) and polylactic acids(PLA). These materials are operated under high-temperature conditions, so high levels of ultrafine particles(mainly nanoparticle size) and chemical compounds such as organic compounds, aldehydes, and toxic gases were identified as being emitted during 3D printing. Conclusions: Personal desktop 3D printers are widely used and expected to be constantly distributed in the future. In particular, hazardous emissions, including nano sized particles and various thermal byproducts, can be released under operation at high temperatures, so it is important to identify the health effects by emissions from 3D printing. Furthermore, appropriate control strategies should be also considered for 3D printing technology.

• Elastomers and Composites
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• v.41 no.4
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• pp.252-259
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• 2006

A new route for making rubber/clay nanocomposites was suggested based on skim natural rubber latex (SNRL), which is a protein rich by-product obtained during the centrifugal concentration of natural rubber (NR) latex. NR/acrylonitrile butadiene rubber (NBR) based nanocomposites were prepared from SNRL and NBR latex of 26 % acrylonitrile content by blending of aqueous dispersion of organoclay (OC) followed by coagulation, drying, mill mixing and vulcanization. X-ray diffraction(XRD) studies revealed that NR/NBR blend nanocomposites exhibited a highly intercalated and exfoliated structure, especially for NBR-rich blends. Dynamic mechanical studies showed that more compatible behavior was observed for NBR-rich blends. The 25/75 NR/NBR blend nanocomposite showed the best mechanical properties.

• Elastomers and Composites
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• v.38 no.3
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• pp.251-261
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• 2003

The flame retardancy and foaming properties of NBR foams containing waste ground tire rubber (GTR) were studied. When the composition ratios of NBR/GTR were ranged in $100/0{\sim}80/20$ (w/w) and rubbers/flame retardants were in the range of $1/1.95{\sim}3.70 wt%$, the considerably optimized foam for flame retardancy was obtained with high limiting oxygen indices (LOI, $29.4{\sim}40.0$), low heat release rate(HRR), closed/semi-closed cell of uniformity, and reasonable expandability ($215{\sim}300 %$). The LOI was increased and the heat release rate was decreased with increasing the amount of GTR content.

• Safety and Health at Work
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• v.12 no.3
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• pp.396-402
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• 2021

Background: Styrene is one of the aromatic compounds used in acetonitrile-butadiene-styrene (ABS) producing petrochemicals, which has an impact on health of workers. Therefore, this study aimed to investigate the health risks of styrene emitted from the petrochemical industry in Iran. Methods: Air samples were collected based on NIOSH 1501 method. The samples were analyzed by the Varian-cp3800 gas chromatograph. Finally, risk levels of styrene's health effects on employees were assessed by the quantitative method of the U.S. Environmental Protection Agency (U.S. EPA) and the semiquantitative way by the Singapore Occupational Safety and Health Association. Results: Based on the results, the employees had the highest average exposure to styrene vapors (4.06 × 10^-1mg.(kg - day)^-1) in the polybutadiene latex (PBL) unit. Therefore, the most top predictors of cancer and non-cancer risk were 2.3×10^-4 and 7.26 × 10^-1, respectively. Given that the lowest average exposure (1.5 × 10^-2mg.(kg - day)^-1) was in the dryer unit, the prediction showed a moderate risk of cancer (0.8 × 10^-6) and non-cancer (2.3 × 10^-3) for the employees. The EPA method also predicted that there would be a definite cancer risk in 16% and a probable risk in 76% of exposures. However, according to the semiquantitative approach, the rate of risk was at the "low" level for all staff. The results showed that there was a significant difference (p < 0.05) between the units in exposure and health risk of styrene (p < 0.05). Conclusion: Given the high risk of styrene's health effects, appropriate control measures are required to reduce the exposure level.