• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.1
• /
• pp.99-104
• /
• 2015

Life rafts, which has been used for domestic vessel currently, are fabricated mostly for the ocean-going vessels in accordance with the SOLAS Resolution. Therefore, there is not any small-sized life raft which can be installed on small fishery boat, leisure boat and cargo vessel with those length shorter than 20 meters in our country. However, in many foreign countries, new standards or the small-sized life rafts applicable to those small vessel have been developed according to the standard of ISO 9650. Furthermore, they make their effort to contribute the safety for the life at sea by supply the superior product of life rafts, which have been adopted by light material (i.e. thermoplastic polyurethane, TPU) and economic production process (i.e. heat sealing, radio-frequency welding, RFW), etc. In this paper, the development results of the small-sized life raft, which has been used the lightening material TPU and fabricated by RF-welding method, will be introduced.

• Advances in nano research
• /
• v.10 no.1
• /
• pp.59-69
• /
• 2021

Electrospinning is a cost-effective and versatile method for producing submicron fibers. Although this method is relatively simple, at the theoretical level the interactions between process parameters and their influence on the fiber morphology are not yet fully understood. In this paper, the aim was finding optimal electrospinning parameters in order to obtain the smallest fiber diameter by using Taguchi's methodology. The nanofibers produced by electrospinning a solution of Thermoplastic Polyurethane (TPU) in Dimethylformamide (DMF). Polymer concentration and process parameters were considered as the effective factors. Taguchi's L9 orthogonal design (4 parameters, 3 levels) was applied to the experiential design. Optimal electrospinning conditions were determined using the signal-to-noise (S/N) ratio with Minitab 17 software. The morphology of the nanofibers was studied by a Scanning Electron Microscope (SEM). Thereafter, a tensile tester machine was used to assess mechanical properties of nanofibrous scaffolds. The analysis of DoE experiments showed that TPU concentration was the most significant parameter. An optimum combination to reach smallest diameters was yielded at 12 wt% polymer concentration, 16 kV of the supply voltage, 0.1 ml/h feed rate and 15 cm tip-to-distance. An empirical model was extracted and verified using confirmation test. The average diameter of nanofibers at the optimum conditions was in the range of 242.10 to 257.92 nm at a confidence level 95% which was in close agreement with the predicted value by the Taguchi technique. Also, the mechanical properties increased with decreasing fibers diameter. This study demonstrated Taguchi method was successfully applied to the optimization of electrospinning conditions for TPU nanofibers and the presented scaffold can mimic the structure of Extracellular Matrix (ECM).

• Applied Chemistry for Engineering
• /
• v.24 no.3
• /
• pp.305-313
• /
• 2013

In this study, we investigated effects of thermal annealing on the thermal properties and microphase separation behaviors of glycidyl azide-based thermoplastic polyurethane elastomers (ETPE). The GAP-based ETPEs were characterized by attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and gel permeation chromatography (GPC). The effects of annealing temperature conditions ($80{\sim}130^{\circ}C$, 1 h or 24 h) on the properties of the ETPEs were investigated. The intensity of azide group absorption peak of ATR-FTIR spectra and the solubility of ETPE for methylene chloride and dimethylformamide solvent decreased after the annealing at $130^{\circ}C$ for 1 h and at $105^{\circ}C$ for 24 h. With increasing the annealing temperature from $80^{\circ}C$ to $110^{\circ}C$, the high temperature rubbery plateau region of storage modulus curves from DMA thermogram for GAP-based ETPEs was extended to the higher temperature.

• Proceedings of the Korean Fiber Society Conference
• /
• 1998.10a
• /
• pp.203-206
• /
• 1998

열가소성 탄성체(Thermoplastic elastomers)의 일종인 polyurethane은 상온보다 높은 유리전이온도(T$_{g}$)를 갖는 hard segment(HS)와 낮은 T$_{g}$를 갖는 soft segment(SS)간의 열역학적 불친화성으로 인해 미세 상분리 구조를 갖는다. SS는 낮은 T$_{g}$로 인해 상온에서 rubbery한 성격을 나타내며 HS는 높은 T$_{g}$로 인해 물리적 가교 역할과 충진제 역할을 한다. Polyurethane은 중합당시의 조성이나 중합방법에 따라 다양한 내부구조를 갖으며 이런 내부구조의 변화에 따른 물리적 성질의 변화 역시 다양하다. (중략)

• 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.

• Fashion & Textile Research Journal
• /
• v.24 no.3
• /
• pp.333-345
• /
• 2022

This study developed and evaluated the motion control of 3D printed fingers applied to smart gloves. Four motions were programmed by assembling the module using the Arduino program: cylindrical grasping, spherical grasping, tip-to-tip pinch gripping, and three-jaw pinch gripping. Cap and re-entrant (RE) strip types were designed to model the finger. Two types of modeling were printed using filaments of thermoplastic elastomer (TPE) and thermoplastic polyurethane (TPU). The prepared samples were evaluated using three types of pens for cylidrical grasping, three types of balls for spherical grasping, and two types of cards for tip-to-tip pinch gripping and three-jaw pinch gripping. The motion control of fingers was connected using five servo motors to the number of each control board. Cylindrical and spherical grasping were moved by controlling the fingers at 180° and 150°, respectively. Pinch gripping was controlled using a tip-to-tip pinch motion controlled by the thumb at 30° and index-middle at 0° besides a three-jaw pinch motion controlled by the thumb-index finger-middle at 30°, 0°, and 0°, respectively. As a result of the functional evaluation, the TPE of 3D-printed fingers was more flexible than those of TPU. RE strip type of 3D-printed fingers was more suitable for the motion control of fingers than the 3D-printed finger.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2010.05a
• /
• pp.24.2-24.2
• /
• 2010

고분자 몰드를 이용한 nanoimprint lithography (NIL)는 고분자소재의 유연성과 투명성으로 인하여, 유기전자소자나 유연한 디스플레이소자 등 다양한 응용이 가능하다. 하지만, 고분자소재는 일반적으로 열저항성과 내구성이 낮아서, 고분자 몰드를 이용한 패턴형성 시, 자외선 경화방식이 주로 사용된다. 만약 복제가 쉽고, 가격이 저렴하며, 열저항성과 내구성이 강한 고분자 몰드를 제작한다면, thermoplastic-NIL 기술에 적용할 수가 있기 때문에, 고온을 요구하는 소자의 패턴형성 공정에 사용 가능하다. 본 연구에서는 이러한 고분자 몰드 제작을 위하여, 열저항성과 내구성이 강한 polyimide 필름과 polyurethane acrylate (PUA)를 기반으로 제작된 resin을 이용하였다. 먼저 Polyimide 필름 위에 자외선 노광을 사용하여, PUA resin 을 경화시킴으로써 패턴을 형성하였다. 이렇게 만들어진 몰드를 thermoplastic-NIL기술에 적용함으로써, Si 기판 위에 sub-마이크로 급 패턴을 형성하였다. 또한, 제작된 고분자 몰드를 사용하여 반복적인 NIL 공정을 수행함으로써 몰드의 내구성을 확인하였으며, 곡면 기판 위에 NIL을 함으로써 몰드의 유연성을 확인 할 수 있었다.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.22 no.5
• /
• pp.5-12
• /
• 2014

Weatherstrip coatings of urethane and silicon type which are fit to EPDM and thermoplastic materials are used in sealing systems for automotive applications for noise reduction and high slip characteristics for external applications, respectively. Polyurethane binder was successfully synthesized from poly(butyladiphate)diol (PBAD), poly(tetramethylene)glycol (PTMG) and isocyanate as starting materials. Then, polyurethane coating agents were prepared by using various additives. To investigate effects of segment types on the abrasion resistance of polyurethane coating agents, thin films based on polyurethane coating materials were fabricated. With increasing the amount of hard segment in the coating agent, abrasion resistance, modulus and tensile strength of the coating films were improved, but the elongation of the coating films was decreased.

• Proceedings of the Korean Fiber Society Conference
• /
• 2002.04a
• /
• pp.243-246
• /
• 2002

자동차 차체 제작을 위해서는 차체의 견고성과 승객의 안전성을 동시에 고려하여 너무 강하거나 너무 무르지 않은 재질의 선택과 차체 설계의 최적화가 요구된다. 본 논문에서는 차량 충돌 시 자동차의 안전도를 향상시키면서 차량의 손상을 최소화 함으로써 수리비를 절감하기 위한 목적으로 TPU(Thermoplastic Polyurethane Elastomer)에 공기를 채워서 만든 에어백 자동차 범퍼를 개발하였다. (중략)

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2006.11a
• /
• pp.78-81
• /
• 2006