• Korean Journal of Materials Research
• /
• v.8 no.1
• /
• pp.19-22
• /
• 1998

polycaprolactone diol(PCL), 4,4'-diphenylmethane diisocyanate(MDI) 및 1,4 butane diol(BD)로부터 segment형 폴리우레탄을 합성하였으며, 이들의 열변형 회복 특성을 조사한 결과 이들 재료들은 전형적인 형상기억 효과를 발휘함을 알 수 있었다. 형상회복온도는 연질성분의 함량 증가와 더불어 증가하였으며, 연질성분의 함량조절로 40-8$0^{\circ}C$의 넓은 범위에서 임의로 조절할 수 있었다.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.18 no.4
• /
• pp.436-441
• /
• 2009

An air filter is a device to remove dust from the air supplied to the automotive engine. A requirement for the optimum air filter is to improve the capability to remove particles from the air it takes in, that is the efficiency and amount of dust collection. By removing dust from the air, the air filter prevents the engine cylinder from wear, reduces ventilation resistance, and thus improves engine output and guarantees intake performance. In order to guarantee such air filter performance, it is very important to properly seal the air filter. For passenger cars made in Korea, the air filters are fabricated with steel caps as their frames are large and their engine capacity is big. Recently however, European countries and Japan started using urethane for manufacturing the air filter, so that all foreign-made cars now have urethane filters. The urethanes used for air filters are applied in two ways: One is to use soft urethane for both top and bottom of the air filter and the other is to use soft urethane for the top and hard urethane for the bottom. Each of these method has unique problems. In this study, hard urethane is used for both top and bottom of the filter in order to improve those problems and increase the sealing efficiency. Especially for the top, NBR (rubber mold) is pre-settled in tough urethane and then the urethane is solidified through foaming, which makes it possible to develop a solid and double-sealed filter.

• Polymer(Korea)
• /
• v.30 no.2
• /
• pp.152-157
• /
• 2006

Anionic or Zwitter-ionic waterbone polyurethanes (WPU) based on mixtures of hydroxy terminated poly-butadiene and poly(propylene glycol) were prepared and their physical properties were characterized. Particle size of WPU increased with increasing the content of HTPB. It was observed that the microphase separation of soft segments and hart segments increased with increasing the content of HTPB in the WPUs. Zwitter-ionic WPU showed stronger hydrogen bonds between molecules than anionic WPU after drying. Polyurethane films obtained after drying of WPUs exhibit besmechanical properties when the HTPB content among polyols for WPUs were 25wt%. It is postulated that such mechanical properties resulted from different microphase separation of soft segments and hard segments of polyurethane films obtainec after drying of WPUs.

• Journal of the Korean Applied Science and Technology
• /
• v.16 no.2
• /
• pp.179-185
• /
• 1999

The effect of blowing agents and inner temperature on the machanical properties of the flexible polyurethane foams were investigated. In the study used that chemical blowing agents is $H_2O$ and support blowing agents. CFC-11, HCFC-114b, dichloromethane, n-penthane, iso-pentane, cyclopentane. The flexible polyurethane foams were foamed by the density of $0.015{\pm}0.002g/cm^3$ and $0.024{\pm}0.002g/cm^3$ which were used in mechanical properties measurements. Inner temperature was measure as long as the preparation of the flexible polyurethane foams of each blowing agents. The density, tensile strength, elongation, tear strength, compression strength and compression set were measured after 48 hours hardening. The result of the study was optimized dichloromethane and cyclopentane at the support blowing agents.

• Applied Chemistry for Engineering
• /
• v.10 no.3
• /
• pp.388-393
• /
• 1999

Polyurethane foams are polymeric material with repeating groups of urethane and urea. When these are heated with ethylene glycol and K acetate catalyst at $200^{\circ}C$, the transesterification of them leads to soluble products. The mechanisms of the reaction were investigated from the molecular weight and the component distributions of the products by GPC and IR analysis. The degradation of the urethane groups was faster than that of urea groups in transesterification reaction. K acetate catalyst accelerated the rate of the transesterification because it had a high ionization tendency. Each reaction, using K or Sr acetate as a catalyst, progressed in the same reaction path but yielded different compositions in products because of the difference of the reaction rate.

• Polymer(Korea)
• /
• v.30 no.3
• /
• pp.247-252
• /
• 2006

The long-term use of indwelling urinary catheters can allow bacterial adhesion to their surfaces, followed by the catheter-associated urinary tract infection. In an attempt to minimize the bacterial adhesion, various amphiphilic polyurethanes (APUs) were synthesized as potential coating materials for urinary catheters. By varying composition of the soft segments such as PEO, PTMO, and PDMS, four different polyurethanes were synthesized. All the APU-coated urinary catheters had the smooth surfaces and showed higher hydrophilicity, compared to the commercial silicone catheters. In particular, the use of APUs with the higher PEG content significantly augmented hydrophilicity and remarkably reduced the total amount of bacteria adhering to the surface. Overall, the APUs prepared in this study provided the promising potential as coating materials for urinary catheters.

• Elastomers and Composites
• /
• v.39 no.4
• /
• pp.286-293
• /
• 2004

Ester- and ether-based thermoplastic polyurethanes of different hardness were injection molded at different mold temperatures and effects of mold temperature on the physical properties of TPUs were investigated. Glass transition temperatures of soft segments of TPUs were hardly changed by mold temperatures. The phase separation of soft and hard segments of injection molded TPUs were affected little by mold temperatures. However, crystallinity of hard segments, temperature range of rubbery plateau, and tensile strength of injection molded TPUs decreased with increasing mold temperatures for TPUs of high hardness. However, injection molded TPUs of low hardness showed increases of crystallinity of hard segments, temperature range of rubbery plateau, and tensile strength with increasing mold temperatures. Different physical properties of injection molded TPUs depending on mold temperatures were attributed to different crystallization and physical crosslinking effects of hard segments.

• Journal of the Korean Institute of Gas
• /
• v.26 no.3
• /
• pp.27-37
• /
• 2022

With the recent increase in the spread of ESS (Electric Storage System), the damage to human life and property is also rapidly increasing due to continuous fires caused by ESS. In the manufacture of urethane sandwich panels used in ESS, it is necessary to improve the flame retardant performance. In this study, in order to realize the flame retardant properties of flexible polyurethane foam, the effect of the tissue density of the product due to the change of the isocyanate functional group parameter that changes the physical properties of the product on the fire performance was studied. The product was manufactured by changing the density of the urethane structure, and combustion performance tests, gas toxicity tests, and smoke density tests were performed. As a result, it was confirmed that the total amount of heat released had excellent performance when the isocyanate functional group was high, and had no correlation with the maximum heat release rate. When the value of the isocyanate functional group was 2.7 or more, the collapse of the shape could be prevented. In the gas hazard test, the performance was increased when the isocyanate functional group was relatively high, so a flame retardant for the Char system, which had a dense structure and easy to form a carbonized film, was added. confirmed to be. Therefore, as a result of this study, it is thought that it will be possible to lay the foundation for the development of a flame retardant to replace the cheap urethane sandwich panel used in the past.

• Journal of Adhesion and Interface
• /
• v.24 no.4
• /
• pp.124-130
• /
• 2023

For automotive coating agents that require little change in characteristics due to changes in external temperature, changes in noise characteristics due to changes in the external environment are very important. Therefore, soft polyurethane with excellent cold resistance, weather resistance, and abrasion resistance, and polysiloxane whose -OH terminated and side chains are modified with amines, are widely used. In this study, coating agents was prepared by adding water-born polyurethane, polysiloxane, ultra high molecular weight polypropylene (UHMWPP) powder, carbon black, and a matting agent to determine the effect of each resin component on noise. To study the effect of each resin component on noise, a coating agent was prepared by adding water-born polyurethane, polysiloxane, UHMWPP powder, carbon black, and a matting agent. The hard/soft segment ratio of water-born polyurethane, the main component of the coating, was 27.1%/72.9%, and the ratio of amino siloxanes to hydroxy-terminated polysiloxane was 2:7, which produced the least noise. The difference in friction coefficient was large when the friction body moves at high speed. When UHMWPP powder replaced SiO₂, noise decreased and gloss also decreased.

• Polymer(Korea)
• /
• v.29 no.2
• /
• pp.140-145
• /
• 2005

Effects of the polyol type and the hard segment content of thermoplastic polyurethane (TPU) on the crystallization of hard segments in TPUs were studied employing differential scanning calorimetry. Diols used for the preparation of TPUs were poly(tetramethylene ether glycol) (PTMEG), poly(propylene glycol) (PPG), polycaprolactone (PCL), poly(butylene adipate) (PBA) the molecular weights of which were 2000 and the hard segments contents of TPUs were $35\~44\;wt\%$. We found that crystallization of hard segments in TPUs were observed at higher temperatures and became faster with increasing hard segment contents of TPUs. The crystallization rate of TPU was also affected by the types of polyols used for the preparation of TPUs. It is postulated that lower miscibility of soft segments and hard segments results in higher crystallization rate and increase of cooling crystallization temperatures due to better hydrogen bending between hard segments in melts.