• Journal of the Korea Concrete Institute
• /
• v.16 no.1 s.79
• /
• pp.54-60
• /
• 2004

This study deals with the setting behavior of polystyrene mortars using waste expanded polystyrene(EPS) solution-based binders. The binders for polystyrene mortars are made by mixing crosslinking agent with EPS solutions prepared by dissolving EPS in styrene. Polystyrene mortars are prepared with various EPS concentrations of EPS solutions and crosslinking agent contents, subjected to a dry curing, and tested for working life, peak exotherm temperature and 10h-length change. From the test results, He working lives of polystyrene mortars are shortened with raising EPS concentration of EPS solution and crosslinking agent content. Low-shrinkage or non-shrinkage polystyrene mortars could be obtained by adjusting EPS concentration of EPS solution and crosslinking agent content.

• Korean Chemical Engineering Research
• /
• v.43 no.4
• /
• pp.511-516
• /
• 2005

In this work, the crosslinked-chitosan microcapsules containing fragrant oil were prepared by oil-in-water-in-oil (O/W/O) multi-emulsion method. The effects of concentration of fragrant oil and stirring rates on the preparing of the microcapsules were investigated. The diameter and form of the microcapsules were observed by scanning electron microscope (SEM). As a result, the average particle size of microcapsules was decreased with increasing the stirring rate. The formation of chitosan microcapsules was comfirmed by FT-IR. The inclusion of fragrant oil into chitosan microcapsules was determined in the presence of specific peak of fragrant oil, i.e., $1,460cm^{-1}$, $2,960cm^{-1}$. Also, the release behavior or profile of fragrant oil from chitosan microcapsules was examined with UV/vis spectra. Released amounts of fragrant oil were increased with increasing as the content of fragrant oil and decreasing the pH.

• Elastomers and Composites
• /
• v.35 no.2
• /
• pp.122-131
• /
• 2000

In this work, the effect of chemical surface treatments on morphology of carbon blacks was investigated in terms of cure behavior and tearing energy ($G_T$) of carbon blacks/rubber composites. As experimental results, the polar or nonpolar chemical treatment led to a significant physical change of carbon black morphology. The cure activation energies (Ea) and frequency factor (A) obtained from Kissinger equation decreased with improving the dispersion of carbon flacks, resulting in high reactivity. However, a significant advantage of carbon black/rubber composites is gained by carbon blacks treated in basic (BCB) or nonpolar (NCB) chemical solution, resulting in increasing the tearing energy. These results could be explained by changes of dispersion, agglomerate, surface functional group, void volume, and cross-linking density of carbon black/rubber composites.

• Korean Journal of Materials Research
• /
• v.7 no.12
• /
• pp.1089-1096
• /
• 1997

본 연구에서는 에폭시/산무수물계에 화학양론비(r=산무수물/에폭시)를 0.5, 0.7,0.9,1.1로 변화시켜 서로 다른 두종류의 경화촉진제 1-cyanoethy1-2-ethy1-4-methy1 imidazole(2E4MZ-CN)과 N,N-dimethy1 benzy1 amine(BDMZ)을 첨가한 시료에 대한 경화거동과 경화 후 물성을 관찰하였다. 이 시료의 등온 경화거동은 동역학 측정기(dynamic mechanical analyzer, DMA)와 시차주사 열량분석기(differential scanning calorimeter, DSC)를 이용하여 조사하였다. DMA로부터 구해진 결과를 보면 경화시 상대저장강성을 (relative storage rigidity, RSR)과 상대손실강성율(relative loss rigidity, RSR)과 상대손실강성율(relative loss rigidity, RLR)의 변화가 r값과 경화촉진제의 종류에 영향을 받았다. 그리고 DSC결과는 r값이 감소함에 따라 경화가 촉진되는 것으로 나타났다. 경화물의 성질을 조사하기 위하여 사용된 DMA로부터 얻어진 유리전이온도(glass transition temperature, T$_{g}$)와 가교결합간의 평균분자량(average molecular weigh between crosslinks, M$_{c}$은 사용한 두 경화촉진제에 대하여 r값의 영향이 다르게 나타났다. BDMA의 경우는 T$_{g}$가 1:1화학양론비인 r=0.9에서 최고치를 보였으나, 2E4MZ-CN은 r이 감소함에 따라 계속 증가하는 양상을 보였다. 이와 같은 경향은 2E4MZ-CN을 경화촉진제로 사용하였을 때 에폭시가 과량으로 될수록 잔류 에폭시기들간의 에케르반응이 추가적으로 일어나 M$_{c}$가 감소하기 때문이다.

• Elastomers and Composites
• /
• v.39 no.1
• /
• pp.42-50
• /
• 2004

In this work, the diglycidylether of bisphenol A (DGEBA) and modified polyurethane (PU) blends were initiated by N-benzylpyrazinium hexafluoroantimonate (BPH). The cure and fracture toughness of neat DGEBA with the addition of PU were investigated. The cure properties of DGEBA/PU blend system were examined by DSC and near-IR measurements. The fracture touhtness were investigated by measuring the critical stress intensity factor ($K_{IC}$) and the critical strain energy release rate ($G_{IC}$). According to the results, the maximum values of owe activation energy ($E_a$) and conversion (${\alpha}$) were found at 10 phr of PU. Also the $K_{IC}$ showed a similar behavior with the results of conversion. These results were probably due to increase of crosslinking density in the blends resulted from increase of the hydrogen bonding between the hydroxyl groups of DGEBA and isocyanate groups of PU.

• Polymer(Korea)
• /
• v.33 no.4
• /
• pp.273-283
• /
• 2009

Recent research issues on the scratch behaviors of polymeric materials has been investigated. In this study, the scratch characterization of polymeric materials with respect of experimental parameters, such as nature of the material, temperature, applied load, test speed, surface treatment, scratch number of times, polymer structure/functional groups, degree of cross-linking, and crystallinity, are reviewed. In addition, the testing standards and methodologies which could quantify the scratch behaviors are introduced and the current international standards are compared and summarized. The latest technical approaches for evaluating the scratch behaviors and improving the scratch resistance of polymers are also discussed.

• Polymer(Korea)
• /
• v.24 no.3
• /
• pp.350-357
• /
• 2000

Curing behaviors of glass/epoxy prepreg for printed circuit boards (PCB) were studied by using dielectrometer and differential scanning calorimeter. This prepreg was showed the lowest ionic viscosity at about 115$^{\circ}C$, and then the ionic viscosity was gradully increased up to 15$0^{\circ}C$. This indicated that the curing reaction of this prepreg started at 115$^{\circ}C$ and the molecular weight was increased by the accelerated thermal cross-linking reaction. The loss factor and tan $\delta$ values were also measured and discussed. The dielectric behaviors of this prepreg system were also measured according to the cure cycle for PCB. This material was found to be thermally stable up to about 30$0^{\circ}C$ and then was showed an abrupt decomposition beyond this temperature.

• Polymer(Korea)
• /
• v.35 no.6
• /
• pp.558-564
• /
• 2011

The biocompatibility and biodegradability of poly(amino acid) make them ideal candidates for many bio-related applications. Poly(aspartic acid), PASP, is one of synthetic water-soluble polymers with proteinlike structure, and has been extensively explored for the potential industrial and biomedical applications due to its biodegradable, biocompatible and pH-responsive properties. In this work, amino acid-conjugated PASPs were prepared by aminolysis reaction onto polysuccinimide (PSI) using ${\gamma}$-aminobutylic acid(GABA) and ${\beta}$-alanine methyl ester and a subsequent hydrolysis process. Their chemical gels were prepared by crosslinking reaction with ethylene glycol diglycidyl ether (EGDE). The hydrogels were investigated for their basic swelling behavior, hydrolytic degradation and morphology. The crosslinked gels showed a responsive swelling behavior, which was dependent on pH and salt concentration in aqueous solution, and relatively fast hydrolytic degradation.

• Elastomers and Composites
• /
• v.38 no.3
• /
• pp.273-280
• /
• 2003

Elastic responses on both pure natural rubber melts with different molecular weights and the rubber compounds mixed with various types of carbon blacks were investigated in this study. Furthermore, the degree of bound rubber was measured for various carbon blacks with different sizes and structures in order to study the interaction between the rubber and carbon blacks, and to study the correlation between the interaction and the elastic responses. As a loading amount of carbon black increased, the degree of bound rubber became higher, particularly far carbon-black particles with smaller sizes and higher structures. The elastic responses of the rubber melt filled with carbon black remarkably improved, as compared with those of unfilled rubber melt, specially in carbon black showing higher contents of bound rubber. Stress relaxation was more delayed and recovery behavior became more elastic, as the molecular weight of the rubber melt increased and the size of carbon-black particles was decreased. Permanent set became higher, as the molecular weight of the rubber melts decreased and the size of carbon-black particles increased.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.2
• /
• pp.200-207
• /
• 2021

The purpose of this study is to investigate experimentally the effects of type of superplasticizer on tensile behavior and cracking pattern of alkali-activated slag-based cementless composite. Three mixtures were prepared according to type of superplasticizer, and the compressive strength and tension tests were performed. Test results showed that differences of tensile strength, tensile strain capacity, and toughness of composites were up to 28.1%, 39.1%, and 66.2%, respectively, according to type of superplasticizer, although fiber balling or poor dispersion of fibers in fresh composites was not observed. It was also observed that the type of superplasticizer influenced number of cracks and maximum fiber bridging stress.