• Elastomers and Composites
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• 제52권1호
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• pp.1-8
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• 2017

Hydrolysis resistance and mechanical property changes of polyketone (POK)/glass fiber (GF) composites were investigated for GF concentrations varying between 30 and 50%. The hydrolysis resistance of GF filled POK and polyamide66 (PA66, hydrolysis resistant grade) composites were compared. As shown by the experimental results, increasing the immersion time of the composites in a monoethylene glycol (MEG)/water solution at $120^{\circ}C$ had no impact or resulted in slightly decreased mechanical properties such as the tensile strength, tensile modulus, and strain at break in case of POK composites, whereas the mechanical properties of PA66 composites showed a significant drop. Increasing GF concentrations increased the tensile strength, tensile modulus, flexural strength, and flexural modulus of POK composites; however, impact strength did not show significant changes. Hydrolysis mechanisms of POK and PA66 are discussed.

• Elastomers and Composites
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• 제52권1호
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• pp.59-68
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• 2017

The effect on the hydrolysis resistance properties by the addition of maleic anhydride grafted EMDM (MA-g-EPDM) and PP (MA-g-PP) to a PA66/GF composite was investigated with respect to the mechanical properties, thermal properties, and morphology. The degree of hydrolysis of the PA66/GF composite was measured using py-GC/MS analysis. When compared to the PA66/GFcomposite in MEG/water solution, the composites where MA-g-EPDM and MA-g-PP were added to PA66/GF showed a higher degree of hydrolysis resistance, impact strength, and thermal properties, whereas their tensile strength, tensile modulus, flexural strength and flexural modulus decreased. As immersion time in the solution increases, the rate of tensile strength drop of the MA-g-PP added composite appeared lower than that of the PA66/MA-g-EPDM/GF and PA66/GF composites. The py-GC/MS analysis confirmed the formation of PA66 hydrolysis reaction by products such as carboxylic acid and alkylamine with increasing immersion time.

• Elastomers and Composites
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• 제48권3호
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• pp.241-248
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• 2013

polyester형 polyurethane foam은 낮은 내가수분해성을 가지므로 quasi prepolymer법에 의한 acrylic polyol을 사용함으로써 극복될 수 있다. acrylic polyol을 함유한 polyurethane foam은 acrylic polyol 함량이 증가함에 따라 인장강도와 경도가 증가하였다. 하지만 split 인열강도와 인열강도는 약간씩 변화되었다. polyurethane foam의 내가수분해성은 인장강도의 손실 백분율로 측정하였으며 acrylic polyol 함량이 25.5g에서 102g으로 증가함에 따라 향상되었다.

• 한국잠사곤충학회지
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• 제40권2호
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• pp.163-168
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• 1998

Hydrolysis rate and activation energy of Antheraea pernyi silk fiber treated with HCI were examined. Thermal decomposition temperature and surface morphology were also investigated by using differential scanning calorimeter and scanning electron microscope. As the concentration of hydrochloric acid and the treatment temperature increased, the hydrolysis occurred more rapidly. The activation energy of Antheraea pernyi, 74.0 kJ/mol, was higher than that of Bombyx mori, 58.1 kJ/mol. As the concentration of hydrochloric acid increases, the activation energy of Antheraea pernyi decreased from 74.0 kJ/mol to 62.0 kJ/mol. The shape of acid-resistance fraction of Antheraea pernyi became more distroyed and was transformed from fiber to powdered form with an increase of hydrolysis rate. The thermal decomposition temperature of Antheraea pernyi was 360.8$^{\circ}C$ until the hydrolysis rate was 81.8 wt%, but ti decreased to 347.0$^{\circ}C$ when the hydrolysis rate was 93.8 wt%.

• 문화기술의 융합
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• 제8권5호
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• pp.553-559
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• 2022

필름의 멀칭 기술은 토양 표면을 덮어 토양 온도와 수분을 조절하고, 잡초를 억제하는 기능에 사용된다. 본 연구에서는 생분해성 멀칭필름의 내가수분해성 및 기계적 물성을 향상시키기 위하여 PBAT(Poly Butylene Adipate-co-Terephthalate)와 PLA(Poly Lactic Acid)를 이축 압출기를 사용하여 개질한 후, 필름의 물성과 생분해 특성을 조사하였다. 멀칭필름을 토양에 매립 후 기간별 필름의 중량감소를 확인하였고, 건답에서 벼농사용 멀칭 후 식물의 성장을 관찰하였다. 내가수분해성이 향상된 멀칭 필름은 작물의 성장에 우수한 특성을 나타냈으며, 생분해되는 멀칭 필름은 환경 친화적이고 효율적이며, 지속가능한 농업관행을 위한 새로운 대안으로써의 가능성을 제공 할 수 있다.

• 접착 및 계면
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• 제13권3호
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• pp.116-120
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• 2012

본 연구에서는 수분산 폴리우레탄의 내가수분해성을 개선하기 위하여 polyester polyol, $H_{12}MDI$, DMPA 및 sulfopropylated polypropyleneglycol-${\alpha}$,${\omega}$-diamine (SP)을 사용하여 수분산 폴리우레탄을 합성하였다. 유리전이온도는 SP 함량의 증가에 따라 증가하다가 NCO/OH 비가 1.8에서는 감소하였다. 또한 SP의 함량이 증가함에 따라 인장강도와 내가수분해성은 증가하는 경향을 나타내었으며, SP로 사슬연장한 WPU-SP에서 인장강도 감소율은 약 WPU-SP-1을 제외한 나머지에서 약 2~5%정도로 내가수분해성이 향상되었다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제15권4호
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• pp.270-275
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• 2015

Purpose : UHMWPE (Ultra-high-molecular-weight-polyethylene) is one of the most widely used material in knife protection clothes because of high strength, elasticity, and light weight. The purpose of this study is to develop the accelerated life test method and predict the lifetime for the knife protection fabric composed by UHMWPE. Methods : In this study, degradation characteristics of UHMWPE fibers and knife protection fabric for cut resistance were evaluated under the hydrolysis and photo-degradation conditions. It was found out that the degradation rate of retained tensile strength was more significant in the photo-degradation than hydrolysis. Therefore, the failure time was determined as the time that the retained tensile strength in photo-degradation is less than 50%. Considering an acceleration factor for irradiance and exposure time, the lifetime was predicted from the calculated failure time. Results : As a result of the accelerated life test, the $B_{10}$ lifetime of knife protection fabric composed by UHMWPE fibers is estimated as 2.8 years for a 90% statistical confidence level. Conclusion: Since the lifetime is predicted by the view-point of radiant exposure in this study, there is a possibility that the estimated lifetime may differ from the actual lifetime. However, it is considered as an useful methodology to estimate the long-term lifetime of knife protection fabrics.

• Nutrition Research and Practice
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• 제7권1호
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• pp.3-8
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• 2013

Buckwheat is known as a health food but is one of the major food allergens triggering potentially fatal anaphylaxis in Asia, especially in Japan and Korea. This study was conducted to investigate the characteristic of enzymatic resistance of buckwheat protein and allergenic potential. Enzymatic resistance of buckwheat protein was performed with in vitro digestibility test in simulated gastric fluid (SGF), pH 1.2, using pepsin and simulated intestinal fluid (SIF) using chymotrypsin. Reactivity of buckwheat proteins to human IgE was performed using six allergic patients sensitized to buckwheat. Buckwheat's IgE levels were measured using the Phadia UniCAP-system. Buckwheat protein, 16 kDa, still remained after 30 min treatment of pepsin on SDS-PAGE. Even though 16 kDa almost disappeared after 60 min treatment, two out of the six buckwheat patients' sera showed reactivity to hydrolysate after 60 min treatment, indicating that allergenicity still remained. In simulated intestinal fluid (SIF) using chymotrypsin, buckwheat protein, 24 kDa, showed resistance to hydrolysis with chymotrypsin on SDS-PAGE, and still had allergenicity based on the result of ELISA. Our results suggest that buckwheat proteins have strong resistance to enzyme degradation. This may be attributed in part to the allergenic potential of buckwheat. Further study should be continued regarding buckwheat allergy.

• Fibers and Polymers
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• 제7권1호
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• pp.1-7
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• 2006

Interaction of a representative antibiotic, doxycycline(Doxy), with commercial poly(acrylonitrile) (PAN) and cationic-dyeable poly(ethylene terephthalate)(PET) fiber was studied in development of infection resistant biomedical materials. Regular PET was also employed for a comparison purpose. Their interactions were investigated at different treatment temperatures, times, and pHs. Fibers were also hydrolyzed by 1% NaOH for 1 or 2 hours at $85^{\circ}C\;and\;100{\circ}C$ to study effect of hydrolysis on antibiotic sorption. Infection-resistant characteristics of the substrates were evaluated by zone of inhibition (ZOI) test. Results revealed that a significant chemical change occurred in PAN and cationic-dyeable PET due to hydrolysis. Additional functional groups obtained by hydrolysis not only enhanced sorption of the antibiotics but also provided greater ZOI values, indicating substantial improvement in sustained infection resistance properties.

• Journal of the Korean Wood Science and Technology
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• 제47권2호
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• pp.200-209
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• 2019

To improve the water resistance of melamine-urea-formaldehyde (MUF) resins, different levels of blocked polymeric 4,4 diphenyl methane diisocyanate (B-pMDI) were blended with MUF resins to prepare B-pMDI/MUF hybrid adhesives, and their adhesion performances were evaluated for the surface lamination of fancy veneer on plywood. FT-IR spectra showed that the de-blocked -NCO groups reacted with the -OH of hydroxymethyl groups of the MUF resins to form urethane bonds at 2% B-pMDI/MUF, which was detected before and after their hydrolysis. The mass loss after the hydrolysis consistently decreased as the B-pMDI level increased, indicating an improvement in the water resistance. As the B-pMDI level increased, the activation energy of hybrid adhesives decreased, which improved the reactivity of the hybrid adhesives. Additionally, the water resistance improvement of the hybrid adhesives increased the tensile shear strength of the surface laminated plywood in semi-water proof and water-proof by 23 % and 8 %, respectively, at 2% B-pMDI level. This was likely due to the urethane linkages in the hybrid adhesives. However, the formaldehyde emission from plywood panels bonded with the hybrid adhesives increased in the dry state, indicating incomplete curing of the hybrid adhesives.