Won Young Jeong

Effects of binder fibers and bonding processes on PET hollow fiber nonwovens for automotive cushion materials

In this study, nonwoven fabrics were developed for the replacement of polyurethane foams in car interiors, in particular, cushioning materials for car seats. Polyethylene terephthalate (PET) hollow fibers and two types of bicomponent binder fibers were used to manufacture automotive nonwovens by carding processes and then post-bonding processes, such as needle punching or thermal bonding. The physical and mechanical properties of nonwovens were thoroughly investigated with respect to the effects of binder fibers and bonding processes. The tensile strength and elongation for nonwovens were found to be significantly improved by combined needle punching and thermal bonding processes. In addition, the nonwoven cushioning materials were characterized in terms of hardness, support factors, and compressive and ball rebound resilience. The nonwovens showed greater hardness than the flexible PU foam. However, support factors over 2.8 for the nonwovens indicated improved seating comfort, along with better seating characteristics of greater resilience and air permeability in comparison with the PU foam.

Reflective composite sheet design for LCD backlight recycling

We have designed a reflective composite sheet consisting of a birefringent polymer matrix and isolated isotropic or minimally birefringent fibers. The optical properties of the sheet have been investigated in terms of the width, spacing, and thickness of the individual fibers. Commercial software (FDTD Solution) was used to simulate the reflectance of the proposed sheet, and conventional processes such as cast-film extrusion in combination with solid-state drawing were used to manufacture the multilayer composite sheet. The measured and simulated reflectance spectra confirm the feasibility of employing the sheet as a reflective polarizer.

Composites of Polyolefin Elastomer Reinforced with Short Carbon Fiber and Its Copolymerization Conditions

To study the effects of short carbon fiber (SCF) on the properties of the polyolefin elastomers (POEs), we prepared the poly(ethylene-co-1-hexene) (PEH)/SCF composites at different percentages of SCF. We also prepared polyethylene (PE)/SCF composites to compare with PEH/SCF composites. PEH was synthesized by the copolymerization of ethylene and 1-hexene using metallocene catalyst/cocatalyst system. Optimum stirring speed, Al/Zr feeding molar ratio, polymerization time, and polymerization temperature were 700 rpm, 600, 30 min, and 60 °C, respectively. We investigated the morphology of the composites using scanning electron microscopy (SEM) and found that the wettability of SCF in PEH/SCF composites was fairly better than that of SCF in PE/SCF composites. It was observed from mechanical tests that the ultimate tensile strength and tensile modulus of PEH/SCF composites were remarkably enhanced as the SCF content increased, whereas those of PE/SCF composites were a little increased. PEH/SCF composites exhibited lower crystallinity than PE/SCF ones. Thermal stability of the composites was enhanced by the addition of SCF.

Fiber-based Diffuser Sheet for Liquid Crystal Display Backlight Unit

A fiber diffuser sheet based on poly (ethylene naphthalate) (PEN) and poly (methylpentene) (PMP) has shown potential for liquid crystal display backlight units, but these materials have an interfacial adhesion problem. To improve the interfacial adhesion between the fibers and matrix components, we have proposed the use of amorphous poly (cyclohexane-1,4-dimethylene terephthalate) (Tritan) instead of PEN. Furthermore, the fabrication processes have been optimized and simplified to improve the optical and mechanical properties of the sheet. As a result, the most effective fiber content for achieving the best haze characteristics of a sample consisting of Tritan and PMP has been identified.

Characterization of Mechanical and Flammability Properties of Nonwoven Fabrics Containing Polyethylene Terephthalate and Polylactic Acid Hollow Fibers

Abstract: The purpose of this study is to develop a lightweight and environmentally friendly nonwoven fabric to sub-stitute polyurethane (PU) foams in automotive interiors. Two types of hollow fibers-polyethylene terephthalate (PET)hollow fiber and polylactic acid (PLA) hollow fiber-and bicomponent binder fibers were used to manufacture the non-woven fabrics for seat cushions by carding, needle punching, thermal bonding, and air through bonding processes. Theideal characteristics required for automotive seat cushions were evaluated, and the significant changes with the struc-tural components were analyzed. The nonwoven fabrics showed better air permeability, compressional resilience, ballrebound resilience, and non-flammability in comparison with PU foams. The characteristics were affected by the man-ufacturing processes. Keywords: nonwoven, PET hollow fiber, PLA hollow fiber, PU foam, automotive seat 1. 서 론 1970년대부터 최근에 이르기까지 자동차산업에서는 자동차의 연비개선과 환경오염의 주원인인 배기가스 저감을목적으로 부품의 일체화, 단순화, 소재의 최적화 등 차량구조 설계와 경량 소재 사용 등으로 차량의 경량화가 추진되고 있다. 자동차 1대당 섬유소재의 양은 1990년대 20kg,2006년에는 28kg, 2010년 약 35kg 정도로 그 사용량이 증가하고 있으며, 최근 금속 차체를 섬유강화복합재료로 대체하려는 연구가 완성단계에 이르고 있어 자동차에서의 섬유사용량 및 이에 따른 경량화는 비약적인 증가세가 예상된다. 자동차 내장재로 사용되는 산업용섬유 중에서 특히부직포 소재는 경량성, 원가절감, 흡·차음 등의 성능향상,성형 및 몰딩기능, 외관의 다양화가 가능하다는 장점을 가지며 자동차 헤드라이너, 대쉬보드, 실내 매트, 도어트림,트렁크 내장재 등에 다양하게 적용되고 있다[1-3]. 차량 경량화와 함께 소비자의 요구가 다양화되고 고급화됨에 따라자동차의 실내·외 정숙성과 주행시 안정감, 쾌적성을 확보하기 위해, 소음과 진동을 제어·차단하는 이른바 NVH(noise, vibration, harshness)에 관한 연구도 활발히 진행되고 있는 실정이다[4-6]. 자동차 및 수송기기용 시트의 쿠션재로는 PU foam이 가장 많이 사용되고 있다. 그러나 PU foam은 사용 중 지속적으로 VOCs를 배출하며 재생 및 재활용이 어렵고 연소시 독성 가스를 배출하는 등 많은 문제점을 가지고 있다.특히, 일본에서는 자동차내의 VOCs로 인한 질환을 SickCar 증후군이라 명명하며 자동차업계, 부품 및 재료업체가협력으로 VOCs 문제에 대응책을 마련하고 있는 실정이다[7,8]. 따라서 본 연구에서는 PU foam을 대체할 수 있는 친환경 부직포 쿠션재의 적용성 연구를 수행하고자 하였다. 중공섬유는 섬유의 내부가 비어 있는 형태로 비중공섬유에 비해 가볍고 중공부분에 채워진 공기로 인하여 보온성,흡음성 등이 뛰어나다는 장점이 있다. 뿐만 아니라 굽힘강성과 반발탄성이 일반섬유에 비해 상대적으로 우수하여 구김이나 압축에 대한 회복성도 크다고 알려져 있다[9-11].따라서 본 연구에서는 자동차 시트용 쿠션재의 친환경 및경량화를 목적으로 재활용 또는 생분해가 가능한 2종의 중

A Study on the Physical Properties of Aramid Fabrics Impregnated with Shear Thickening Fluid

Fabric construction affects the friction between yarns, which is a very important parameter on energy absorption and propagation. This study reports the physical properties dependent on the weaving density and STF (shear thickening fluid) impregnated aramid fabrics. To improve the frictional force between yarns, STF was applied on Kevlar woven fabrics. STF/Kevlar composite was composed of Kevlar woven fabrics impregnated with fumed silica dispersed in poly-ethylene glycol. The results demonstrated that the yarn pull-out force of neat Kevlar fabrics increased linearly as the fabric count increased. In the case regarding STF impregnated Kevlar fabrics, the pull-out force increased exponentially as the fabric count increased. Considering the ballistic performance of the fabric is related to the pull-out force of yarns in the fabric, the STF/Kevlar composite with high density woven fabrics can be a decent material for bullet-proof equipment.