• Elastomers and Composites
• /
• 제46권3호
• /
• pp.195-203
• /
• 2011

친환경 소재인 바이오복합재료(bio-composites)의 제조를 위하여 기질 고분자로는 poly(lactic acid) (PLA)를 그리고 충전제(filler)로는 케나프 섬유(kenaf fiber)를 사용하였다. 또한 섬유와 고분자 사이의 계면결합 향상을 위해 아세틸화 케나프 섬유(acetylated kenaf fiber)와 상용화제(compatibilizer)를 첨가해 주었다. 본 연구에서는 화학처리와 상용화제가 기계적-점탄성과 형태학적 특성에 미치는 영향을 평가하였고, 섬유가 소수성이 될수록 기질 고분자와 높은 계면결합을 가지며 물성과 형태학적 성질 또한 향상된다는 결과를 보여줬다. 그러나 점탄성과 유리전이온도에는 큰 영향을 미치지 않는다는 사실을 확인하였다.

• Tribology and Lubricants
• /
• 제31권5호
• /
• pp.195-204
• /
• 2015

Several researches are focused on improving the value of fine chemicals based on biomass resources due to environmental and other concerns associated with the use of petroleum-based products. Therefore, the synthesis and application of estolides derived from plant-based waste oil materials and their application as lubricants and as processing oil for butyl rubber products have been studied. Four kinds of estolide were prepared with conversions of 71~92% over 24h using various vegetable oils, as determined by size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. FT-IR spectroscopy determines the esterification of estolides using 2-ethylhexyl alcohol. The estolides have iodine values of 35~90, α-ester/α-acid ratios of 0.45~0.55, and total acid number of 114~134 mg KOH g^–1. Four ball wear tests show that the wear scar diameters (WSDs) of estolides as base oil significantly decreased to 0.328~0.494 mm, compared to WSDs of 0.735 and 0.810 mm of WSD for 150N and Yubase 6, respectively, as general base oil. Thus, the estolides have better wear resistance and satisfying design objectives for the engineering of a variety of lubricant base oils.

• 접착 및 계면
• /
• 제11권2호
• /
• pp.57-62
• /
• 2010

광원경화형 소재는 UV, 가시광선 등에 의해 반응하여 분자간의 가교가 일어나고 이러한 가교반응에 의해 물성이 제어되는 소재를 의미한다. 광원경화거동과정에서 수축현상이 발생하게 되는데 이때 발생하는 수축현상으로 인해 재료의 구조가 변하고 내부의 응력이 발생하는 현상 등의 문제가 발생한다. 열경화에 의한 수축현상을 분석하는 연구는 많이 진행되어 왔으나 광원경화에 대한 수축현상을 연구하는 분야는 현재 경화 수준이나 경화속도 등을 분석하는데 그치고 있다. 본 연구에서는 수축률 측정기를 통해 광원경화에 대한 수축현상을 실시간으로 살펴보고 재료의 차이에 따른 경화거동과 수축현상의 차이를 살펴보고자 한다. 관능기의 숫자가 변화함에 따라 수축률과 수축 속도의 변화가 생겼으며 분자량의 사슬길이에 따라 수축정도의 차이가 발생했다. 이러한 결과가 이론적인 결과 값인 양의 상관관계와는 반대로 음의 상관관계를 가짐을 분석하였다. 이는 수축률이 단순히 분자량과 관능기 숫자에 따라 결정되는 것이 아니라 분자구조에 따른 혼합물 내에서의 유동성 등에도 영향을 받음을 확인 할 수 있는 결과이다.

• Journal of the Korean Wood Science and Technology
• /
• 제43권1호
• /
• pp.86-95
• /
• 2015

본 연구는 기존에 제조되었던 교호집성재의 휨강도의 단점을 보완하고 새로운 특성을 가진 교호 집성재 즉, 합판을 코어로 이용한 집성재가 가진 기계적강도의 효과를 알아보기 위해 수행되었다. 집성재와 합판의 구성 방법, 적층 방향에 따라 그 값을 비교하였으며, 그에 따른 휨강도와 탄성계수를 측정하여 분석한 결과, 중심부를 집성판과 합판을 혼합하여 구성한 합판 코어 집성재의 휨강도(MOR) 값이 59.6% 강도가 향상되어 교호집성재구조 대조군보다는 우수하고, 집성재구조 대조군과는 유사한 강도를 나타냈다. 휨탄성계수(MOE)는 합판 코어 집성재의 구조 및 적층 방향성에 상관없이 모두 집성재구조 대조군과 유사한 MOE 값을 나타냈다. 치수 안정성 실험에서는 합판을 코어에 사용한 합판코어 집성재가 합판 사용으로 인하여, 수축 팽창률 모두 집성재와 교호집성재구조 대조군에 비해서 더 안정적인 것으로 나타났다.

• Journal of Magnetics
• /
• 제11권4호
• /
• pp.189-194
• /
• 2006

The recent development of bio-conjugated magnetic nanoparticles offers many opportunities for applications in the field of biomedicine. In particular, the use of magnetic nanoparticles for biosensing has generated widespread research efforts following the progress of various magnetic field sensors. Here we demonstrate substrate-free biosensing approaches based on the Brownian rotation of ferromagnetic nanoparticles suspended in liquids. The signal transduction is through the measurement of the magnetic ac susceptibility as a function of frequency, whose peak position changes due to the modification of the hydrodynamic radius of bio-conjugated magnetic nanoparticles upon binding to target bio-molecules. The advantage of this approach includes its relative simplicity and integrity compared to methods that use substrate-based stray-field detectors.

• 한국가구학회지
• /
• 제28권2호
• /
• pp.111-117
• /
• 2017

Recently, as people's interest in wood has increased, the use of wood as household and landscape decking materials has increased. As the deck material, imported wood such as synthetic wood, Ipe, and Malas was used in addition to the existing preserved wood, but recently deck use has been activated as part of the activation of domestic materials. As an important quality factor in the selection of such decking materials, various durability along with weatherability for long - term use is required for maintenance. Generally used tropical hardwoods have excellent weatherability and durability without additional preservative treatment. However, the domestic larch is a wood species with a higher specific gravity and durability than ordinary conifers. However, it has not yet been used as a deck material due to lack of comparative studies on its characteristics. Therefore, hardness and durability of wood were measured using six specimens of Ipe, Massaranduba, Malas, Douglas-fir, Larch and Torrefied-Larch. Density Profile was used to measure the density, and Brinell hardness test and resistance test against momentary impact were carried out for the test of resistance to static load. Also, The hardness and durability of wood were measured by castor test with resistance test against dynamic load, as well as, nail down test by experiment on surface hardness and durability. As a result of the experiment, the hardness was increased in proportion to the density, and it was confirmed that the imported lumber was harder and durable than the domestic larch.

• Journal of the Korean Wood Science and Technology
• /
• 제37권2호
• /
• pp.155-163
• /
• 2009

This study examined the thermal stability of PLA-WF bio-composites. Wood flour (WF)-filled PLA bio-composites were reinforced with the flame retardants, Melamine pyrophosphate (MPP), resorcinol bis (diphenyl phosphate) (RDP) and zinc borate (ZB). The flame retardant was compounded with PLA and natural biodegradable filler. The thermal properties of the biodegradable polymer and bio-composites reinforced with the flame retardant were measured and analyzed by DSC, DMA and TGA. The results showed that the flame retardant-reinforced biodegradable bio-composite exhibited improved thermal properties.

• 접착 및 계면
• /
• 제8권4호
• /
• pp.32-40
• /
• 2007

• Tribology and Lubricants
• /
• 제30권6호
• /
• pp.323-329
• /
• 2014

The friction-reducing properties of lubricants containing ionic liquids based on ammonium dithiocarbamate are studied. The ionic liquids are produced through the following two steps: the synthesis of sodium alkyl dithiocarbamates via the substitution reaction of dialkylamine and carbon disulfide and their subsequent conversion into ammonium dithiocarbamate-based ionic liquids through an ion-exchange reaction with a quaternary alkyl ammonium halide salt. The structures of the ionic liquids are characterized by NMR spectroscopy and Fourier transform infrared spectroscopy. The isolated yields of the ionic liquids, which are viscous and pale yellow, are approximately 92%. The Brookfield viscosities and pour points of the ionic liquids are determined. Further, their wear resistances are measured through the four-ball wear test and the Schwingung Reibung Ver-schleiss (oscillation, friction, wear) test. The wear scar diameter of the lubricants containing 1 wt of the quaternary alkyl ammonium dithiocarbamate-based ionic liquids (0.475-0.631 mm) is significantly lower than that of the base oil (0.825 mm), proving that the ammonium dithiocarbamate-based ionic liquids have good friction-reducing characteristics. However, these friction-reducing characteristics fade significantly after long-term storage, owing to the degradation of the ionic liquids.

• Elastomers and Composites
• /
• 제54권3호
• /
• pp.225-231
• /
• 2019

Bio-based polyester polyol was synthesized via esterification between azelaic acid and isosorbide. After esterification, bio-based polyurethanes were synthesized using polyester polyol, 1,3-propanediol as the chain extender, and 4,4'-diphenylmethane diisocyanate, in mixing ratios of 1:1:1.5, 1:1:1.8, 1:1:2, and 1:1:2.3. The bio TPU (Thermoplastic Polyurethane) samples were characterized by using FT-IR (Fourier Transform Infrared Spectroscopy), TGA (Thermal Gravimetric Analysis), DSC (Differential Scanning Calorimetry), and GPC (Gel Permeation Chromatography). The mechanical properties (tensile stress and hardness) were obtained by using UTM, a Shore A tester, and a Taber abrasion tester. The viscoelastic properties were tested by an Rubber Processing Analyzer in dynamic strain sweep and dynamic frequency test modes. The chemical resistance was tested with methanol by using the swelling test method. Based on these results, the bio TPU synthesized with the ratio of 1:1:2.3, referred to as TPU 4, showed the highest thermal decomposition temperature, the largest molecular weight, and most compact matrix structure due to the highest ratio of the hard segment in the molecular structure. It also presented the highest tensile strength, the largest elongation, and the best viscoelastic properties among the different bio TPUs synthesized herein.