• 한국염색가공학회지
• /
• 제21권4호
• /
• pp.39-45
• /
• 2009

PVA films were crosslinked with dimethylol dihydroxy ethylene urea (DMDHEU) and three polycarboxylic acids of butanetetracarboxylic acid (BTCA), citric acid and malic acid Different factors influencing the crosslinking treatment with BTCA were investigated including BTCA and sodium hypophosphite (SHP) concentration, curing temperature and time. The cured films was extracted with boiling water and gel fraction was calculated based on weight change of the PVA films. The gel fraction of PVA films increased with increasing curing temperature and time. And the resistance to water and thermal stability of the crosslinked PVA films improved with the BTCA crosslinking treatment. While crosslinking with citric acid gave the highest gel fraction among the crosslinkers, crosslinking with malic acid showed the highest absorbancy in 0.9% saline solution, which was attributed to lower crosslink density and high number-average molecular weight between crosslinks. The superabsorbent PVA films could be prepared by adjusting the crosslinking condition of PVA with polycarboxilic acids.

• 폴리머
• /
• 제26권1호
• /
• pp.80-87
• /
• 2002

전자선 및 열경화 방법을 사용한 에폭시 수지의 경화거동과 열안정성 효과를 알아보기 위하여 비교 연구를 수행하였다. 본 연구에서는, benzylquinoxalinium hexafluoroantimonate(BQH)가 에폭시 수지의 잠재성 양이온 촉매로서 사용되었다. 열중량분석(TGA)에 의하면, Coats-Redfern 방법에 기초한 분해활성화 에너지는 열경화 방법의 경우가 더 높게 나타났다. 이것은 열로 경화되어진 에폭시 수지의 높은 가교 밀도로 인해 열확산 속도가 느려졌기 때문으로 사료된다. 그러나, 전자선 방법으로 경화되어진 에폭시 수지에서는 안정한 짧은 고리구조, 적분열분해온도, 그리고 높은 충격강도를 위한 최종적인 연성 특성을 향상시키는 수산화기의 증가가 근적외선 분광기(NIRS) 측정으로 관찰되었다.

• Elastomers and Composites
• /
• 제55권1호
• /
• pp.13-19
• /
• 2020

4,4'-Methylenebis(2-chlorobenzenamine) (MOCA)-free fast curing polyurethanes were prepared. In this study, the processibility of a fast curing polyurethane system was characterized by assessing the pot life. The obtained pot life of the polyurethane was 6-8 s, indicating that this prepolymer-curative system is appropriate for ribbon flow casting. The influence of the NCO index on the viscosity and mechanical properties was evaluated. The viscosity, tensile strength, tear strength, and hardness of the as-prepared polyurethanes showed an increasing trend, with an increase in the NCO index, whereas the elongation at break increased initially and then decreased with an increase in the NCO index. The gel fraction and crosslink density showed a direct correlation with the NCO index, which substantiated the improved mechanical properties at the higher NCO index. The coefficients of friction and abrasion deteriorated with an increase in the NCO index.

• 한국염색가공학회지
• /
• 제24권4호
• /
• pp.281-287
• /
• 2012

Poly(phenylene sulfide) films containing acetophenone as a photoinitiator were photocrosslinked under UV irradiation using a continuous UV irradiator. The gel fraction of the irradiated PPS in 1-Chloro naphthalene reached 94.7% with increasing UV energy and the photoinitiator concentration in the film upto $200J/cm^2$ and 12wt% respectively. Solid state $^1C$ NMR analysis suggested that the crosslinking occurred between the phenylene chains in PPS, indicating that the acetophenone may the phenylene hydrogens and subsequently adjacent polymer radicals could be recombined to form the crosslinked structure. The crosslinking improved the thermal behavior of PPS such as loss of $T_g$ and $T_c$, higher melting point and lower melting enthalphy as well as significantly higher peak pyrolysis temperature as much as $63.5^{\circ}C$. Surprisingly the tensile toughness of the most crosslinked PPS increased by 842%, resulting from the substantial enhancements in tensile modulus, strength and strain as much as 76%, 236% and 240% respectively. Also dynamic mechanical measurement indicated that the distance between crosslinks in the crosslinked PPS reached 85.3 g/mol corresponing to a crosslink density of 0.012 mol/g.

• Elastomers and Composites
• /
• 제41권1호
• /
• pp.10-18
• /
• 2006

Maleic anhydride로 처리된 저분자량 폴리부타디엔 (액상 PB)이 실리카로 보강된 SBR 배합물의 특성에 미치는 영향을 연구하였다. 실리카 분산은 액상 PB의 첨가에 의해 향상되었다. Maleic anhydride가 포함된 액상 PB가 maleic anhydride가 포함되지 않은 액상 PB보다 실리카 분산성 향상에 더 효과적임을 알 수 있었다. SBR 배합물의 점도는 액상 PB가 첨가됨에 따라 감소하였다. 가교밀도는 액상 PB의 함량이 증가함에 따라 감소하였고 가황 속도는 느려졌다. 실험 결과를 고려하면, 5 phr 이하의 소량으로 액상 PB를 첨가함으로써 실리카로 보강된 SBR 배합물의 특성을 향상시킬 수 있을 것으로 사료된다.

• Elastomers and Composites
• /
• 제38권1호
• /
• pp.65-71
• /
• 2003

저분자량 SBR (액상 SBR)이 실리카로 보강된 SBR 배합물의 특성에 미치는 영향에 대해 연구하였다. 액상 SBR을 실리카로 보강된 SBR 배합물에 첨가하면 점도가 낮아졌다. 가교밀도는 액상 SBR의 함량이 증가함에 따라 감소하였고 가창속도는 느려졌다. 모듈러스와 인장강도는 액상 SBR의 함량이 증가할수록 낮아졌고 신율은 증가하였다. 마모 특성은 액상 SBR의 함량에 따라 큰 차이를 보이지 않았다. 이는 액상 SBR의 첨가에 의해 실리카 분산이 향상되었기 때문으로 여겨진다. 실험결과를 종합해 볼 때, 5 phr 이하의 적은 양의 액상 SBR을 사용하는 것이 실리카로 보강된 SBR 배합물의 특성을 향상시키는데 바람직할 것으로 판단된다.

• Korean Chemical Engineering Research
• /
• 제59권1호
• /
• pp.112-117
• /
• 2021

본 연구에서는 생물학적 공유결합인 다이타이로신 결합을 모방하여 비가역적 공유결합을 기반으로 한 펩타이드의 자기조립 방법을 연구하였다. 고밀도의 다이타이로신 결합을 달성하기 위해 Tyr-Tyr-Leu-Tyr-Tyr (YYLYY) 의 서열을 갖는 펩타이드 단량체를 선택하였다. 다이타이로신 결합으로 자기조립 된 펩타이드 나노입자는 가시광선 하에서 Ru(BPY)3Cl2 촉매를 사용하여 단일공정 광가교를 통해 합성되었다. 펩타이드 나노 입자의 크기에 대한 각 성분의 농도 효과는 동적 광산란, UV-Vis 분광법 및 투과 전자 현미경을 사용하여 확인하였다. 이를 통해 130 nm~350 nm범위의 펩타이드 나노입자의 크기별 최적의 합성 조건을 제시하였다.

• Elastomers and Composites
• /
• 제56권1호
• /
• pp.32-42
• /
• 2021

The vulcanizate structure of silica-filled compounds is affected by the filler-rubber interaction (FRI) due to the silica-rubber coupling reaction and the chemical crosslink density (CCD) of the matrix rubber. In this study, the vulcanizate structure changes of silica-filled compounds according to the silane and sulfur variation were quantitatively analyzed using the Flory-Rehner and Kraus equations. In efficiency vulcanization (EV) conditions with low sulfur content, FRI increased when the bis-[3-(triethoxysilyl)propyl]tetrasulfide (TESPT) content increased, and the CCD clearly decreased. By contrast, in semi-EV conditions with high sulfur content, as TESPT content increased, the FRI increased the same way EV conditions, but the CCD was unchanged. Based on these results, it was confirmed that FRI of the silica-filled compounds increased as TESPT content increased, but CCD decreased or retained similar values according to the vulcanization system, indicating that the formation reaction of FRI was preferred over CCD.

• Elastomers and Composites
• /
• 제58권3호
• /
• pp.136-141
• /
• 2023

Polyacrylic rubber (ACM) is well known for its excellent heat resistance and chemical stability. Additionally, its performance can be readily manipulated by modifying its functional groups, rendering it highly attractive to various industries. However, extreme climate changes have necessitated an expansion of the operating temperature range and lifespan of ACM products. This requires the optimization of both the compounding process and functional-group design. Hence, we investigated the relationship between the cross-linking system and mechanical properties of an ACM with a carboxylic cure site. The crosslink density is determined by chemical kinetics according to the structure of additives, such as diamine crosslinkers and guanidine accelerators. This interaction enables the manipulation of the scotch time and mechanical properties of the compound. This fundamental study on the correlation analysis between cross-linking systems, physical properties, and storage stability can provide a foundation for material research aimed at satisfying the increasingly demanding service conditions of rubber products.

• Nuclear Engineering and Technology
• /
• 제52권6호
• /
• pp.1297-1303
• /
• 2020

In this study, nuclear radiation shielding and rigidity parameters of Y (0.1-x)B0.6Bi1.8O3La2x glassy system were investigated in order to determine it's suitability for use as nuclear radiation shielding materials. Therefore, a group of bismuth borate glass samples with La₂O₃ additive were synthesized using the technique of melt quenching. According to the results, the increase of the La₂O₃ additive increases the density of the glass samples and the mass attenuation coefficient (μ_m) values, whereas the half-value layer (HVL) and mean free path (MFP) values decrease. The effective atomic number (Z_eff) is also enhanced with an increment of both mass removal cross section for neutron (Σ_R) and absorption neutron scattering cross section (σ_abs). In addition to the other parameters, rigidity parameter values were theoretically examined. The increase of La₂O₃ causes some other important magnitudes to increase. These are the average crosslink density, the number of bonds per unit volume, as well as the stretching force constant values of these glass samples. These results are in concordance with the increase of elastic moduli in terms of the Makishima-Mackenzie model. This model showed an increase in the rigidity of the glass samples as a function of La₂O₃.