• Advanced Composite Materials
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• v.17 no.1
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• pp.25-40
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• 2008

The research and development in soundproof materials for preventing noise have attracted great attention due to their social impact. Noise insulation materials are especially important in the field of soundproofing. Since the insulation ability of most materials follows a mass rule, the heavy weight materials like concrete, lead and steel board are mainly used in the current noise insulation materials. To overcome some weak points in these materials, fiber reinforced composite materials with lightweight and other high performance characteristics are now being used. In this paper, innovative insulation sheet materials with carbon and/or glass fabrics and nano-silica hybrid PU resin are developed. The parameters related to sound performance, such as materials and fabric texture in base fabric, hybrid method of resin, size of silica particle and so on, are investigated. At the same time, the wave analysis code (PZFlex) is used to simulate some of experimental results. As a result, it is found that both bundle density and fabric texture in the base fabrics play an important role on the soundproof performance. Compared with the effect of base fabrics, the transmission loss in sheet materials increased more than 10 dB even though the thickness of the sample was only about 0.7 mm. The results show different values of transmission loss factor when the diameters of silica particles in coating materials changed. It is understood that the effect of the soundproof performance is different due to the change of hybrid method and the size of silica particles. Fillers occupying appropriate positions and with optimum size may achieve a better effect in soundproof performance. The effect of the particle content on the soundproof performance is confirmed, but there is a limit for the addition of the fillers. The optimization of silica content for the improvement of the sound insulation effect is important. It is observed that nano-particles will have better effect on the high soundproof performance. The sound insulation effect has been understood through a comparison between the experimental and analytical results. It is confirmed that the time-domain finite wave analysis (PZFlex) is effective for the prediction and design of soundproof performance materials. Both experimental and analytical results indicate that the developed materials have advantages in lightweight, flexibility, other mechanical properties and excellent soundproof performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.6
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• pp.594-602
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• 2022

Cast-resin transformers are widely installed in various electrical power systems because of their low operating cost and low influence on external environmental factors. However, when they have an internal defect during the manufacturing process or operation, a partial discharge (PD) occurs, and eventually destroys the insulation. In this paper, a Rogowski-type PD sensor was studied to replace commercial PD sensors used for the insulation diagnosis of power apparatus. The proposed PD sensor was manufactured with four different types of PCB-based winding structures, and it was analyzed in terms of the detection characteristics for standard calibration pulses and the changes of the output voltage according to the distance. The output increased linearly in accordance with the applied discharge amount. It was confirmed that the hexagon structure sensor had the highest sensitivity, because the winding cross-sectional area of the sensor was larger than others. In addition, as the distance from the defect increased, the output voltage of the sensors decreased by 7.32% on average. It was also confirmed that the attenuation rate according to the distance decreased as the input discharge amount increased. For the application of this new type sensor, PD electrode system was designed to simulate the void defect. Waveforms and PRPD patterns measured by the proposed PD sensors at DIV and 120% of DIV were the same as the results measured by MPD 600 based on IEC 60270. The proposed PD sensors can be installed on the inner wall of the transformer tank by coating its surfaces with a non-conductive material; therefore, it is possible to detect internal defects more effectively at a closer distance from the defect than the conventional sensors.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.767-771
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• 1999

Poly(ester-imide)(PEI) for the electrical insulation coating was synthesized and evaluated with one-step method as well as two-step method. For the synthesis of poly(ester-imide), imide repeat unit of N,N'-(4,4'-diphenylmethane) bistrimellitimide(DID) was initially made from trimellitic anhydride(TMA) and methylene dianiline(MDA), followed by the second stage reaction of esterification. One-step reaction was performed by reaction of TMA, MDA, dimethyl terephthalate(DMT), ethylene glycol(EG), and 1,3,5-tris-(2-hydroxy ethyl) isocyanurate(THEIC) in m-cresol solvent at a time. The synthesized poly(ester-imide) was cured with xylene, P-5030K(phenol-formaldehyde resin), TK-8(TDI type blocked polyisocyanate) and tetrapropyltitanate(TPT). It was found that the content of hydroxyl group, amount of DMT, and imide repeat unit played important role for the properties of electrical insulation coating film.

• Clean Technology
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• v.29 no.4
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• pp.237-243
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• 2023

Aerogel is the most excellent insulation material known to date, but it is inflexible and has very low strength. A blanket containing aerogel in a nonwoven fabric or fiber is currently the most practical form. However, aerogel blankets are not yet widely used because they cannot avoid dust generation when handled, lack flexibility, and can possibly deform. In this study, vacuum treatment, surface treatment, and composite materialization technology were applied to solve this problem, and some prototypes were also made. If an aerogel blanket is wrapped in an aluminum sheet, sealed at the four ends, and vacuumed, it can become a material with better insulation than the blanket itself. An aerogel molded body can be made by coating the aerogel blanket with resin and treating the surface. If the aerogel blanket is multi-packed and laminated with resin or fiber in multiple layers to make it a composite material, it can be used as a flexible insulation material. In particular, this composite material, which utilizes a Teflon membrane with controlled pores, is breathable and waterproof, so it can be used for clothing. Prototypes of insoles for winter boots and outdoor roll mats were also produced using aerogel blanket resin and fiber composites. These prototypes showed low thermal conductivity of less than 20 mW m^-1K^-1, with good flexibility and durability.

• Progress in Superconductivity and Cryogenics
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• v.16 no.1
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• pp.14-18
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• 2014

The mechanical, electrical and thermal characteristics of insulating materials may significantly affect the performance and reliability of electrical devices using superconductors. General method to provide insulating layer between coated conductors is wrapping coated conductor with Kapton tape. But uniform and compact wrapping without failure or delamination in whole coverage for long length conductor is not a simple task and need careful control. Coating of insulating layer directly on coated conductor is desirable for providing compact insulating layer rather than wrapping insulating layers around conductor. Ceramic added polymer has been widely used as an insulating material for electric machine because of its good electrical insulating properties as well as excellent heat resistance and fairy good mechanical properties. The insulating layer of coated conductor should have high breakdown voltage and possesses suitable mechanical strength and maintain adhesiveness at the cryogenic temperature where it is used and withstand stress from thermal cycling. The insulating and mechanical properties of polymer can be improved by adding functional filler. In this study, insulating layer has been made by adding ceramic particles such as $SiO_2$ to a polymer resin. The size, amount and morphology of added ceramic powder was controlled and their effect on dielectric property of the final composite was measured and discussed for optimum composite fabrication.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.149-154
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• 2018

This paper describes the fabrication and heat transfer property of 50 watts rated LED array module where multiple chips are mounted on chip-on-board type ceramic-metal hybrid substrate with high heat dissipation property for high power street and anti-explosive lighting system. The high heat transfer ceramic-metal hybrid substrate was fabricated by conformal coating of thick film glass-ceramic and silver pastes to form insulation and conductor layers, using thick film screen printing method on top of the high thermal conductivity aluminum alloy heat-spreading panel, then co-fired at $515^{\circ}C$. A comparative LED array module with the same configuration using epoxy resin based FR-4 PCB with thermalvia type was also fabricated, then the thermal properties were measured with multichannel temperature sensors and thermal resistance measuring system. As a result, the thermal resistance of the ceramic-metal hybrid substrate in the $4{\times}9$ type LEDs array module exhibited about one third to the value as that of FR-4 substrate, implying that at least triple performance of heat transfer property as that of FR-4 substrate was realized.