• Elastomers and Composites
• /
• v.53 no.3
• /
• pp.175-180
• /
• 2018

Solution-styrene-butadiene rubber (SSBR) composites were manufactured using four kinds of fillers: silica-silane coated carbon black (SC-CB) hybrid, starch-SC-CB hybrid, pure silica, and pure starch. The influence of filler type on the mechanical properties of the rubber matrix was studied in this work. SC-CB was prepared by silane-graft-coating using vinyl triethoxy silane and carbon black, which enhanced the dispersion effect between the rubber matrix and the filler, and improved the mechanical properties of the compounds. The morphology of the composites was observed by field-emission scanning electron microscopy (FE-SEM). The thermal decomposition behavior of the composites was determined by thermogravimetric analysis (TGA), and the crosslinking behavior of the composites was tested using a rubber process analyzer (RPA). The hardness, tensile strength, swelling ratio, and gas transmittance rate of the composites were evaluated according to ASTM. The test results revealed that with the addition of SC-CB, the hybrid fillers, especially those blended with silica, showed a better reinforcement effect, the highest hardness and tensile strength, and stable thermal decomposition behavior. This implies that the silica-SC-CB hybrid filler has a notable mechanical reinforcement effect on the SSBR matrix. Because of self-crosslinking during its synthesis, the starch-SC-CB hybrid filler produced the most dense matrix, which improved the anti-gas transmittance property. The composites with the hybrid fillers had better anti-swelling properties as compared to the neat SSBR composite, which was due to the hydrophilicity of silica and starch.

• Polymer(Korea)
• /
• v.35 no.4
• /
• pp.332-336
• /
• 2011

Hydrogels have been investigated due to their potential in a myriad of applications. The introduction of functional moiety such as sulfide has expanded their applicability. In this study, an investigation was carried out on the introduction of fucoidan into the hydrogels of clay/acrylamide. In the resulting semi-IPN nanocomposite hydrogels, the linear polysaccharide, fucoidan, has strong ionic interactions with clay. It was also confirmed from simple mixing tests that fucoidan can physically crosslink with clay without chemical crosslinks. In the semi-IPN hydrogels, equilibrium swelling ratio increased with the content of fucoidan. Elastic modulus increased with an initial increase in the content of fucoidan, and decreased with a further increase. The work of fracture results of these hydrogels showed their tough properties. These hydrogels could provide functional properties such as mucoadhesiveness with tunable hydrogel characteristics.

• Journal of the Korean Wood Science and Technology
• /
• v.48 no.1
• /
• pp.32-40
• /
• 2020

While the utilization of wood as a raw material in related industries has been increasing with the population increasing, the availability of wood from natural forests has continued to decline. An alternative to this situation is the manufacture of particleboard from non-wood lignocellulose materials through the modification of sandwich particleboard (SPb) using bamboo strands as reinforcement. In this study, strandsof belangke bamboo (Gigantochloa pruriens W) and tali bamboo (Gigantochloa apus) were utilized. The non-wood particles included sugar palm fibers, cornstalk, and sugarcane bagasse. The board was made in a three-layer composition of the face, back, and core in a ratio of 1: 2: 1. The binder used was 8% isocyanate resin. The sheet was pressed at a temperature of 160℃ for 5 min under a pressure of 3.0 N/㎟. Testing included physical and mechanical properties based on the JIS A 5908 (2003) standard, while acoustic testing was based on ISO 11654 (1997) standards. The results showed that using bamboo strands as reinforcement has an effect on the mechanical and physical properties of SPb. Almost all the types of boards met the JIS A 5908 (2003) standards, with the exception of thickness swelling (TS) and internal bond (IB) parameters. Based on the thickness swelling parameter, the C-type board exhibited the best properties. Overall, the B-type board thatused a belangke bamboo strand for the surface and sugarcane bagasse as the core underwent the best treatment. Based on the acoustical parameter, boards using a tali bamboo strand for the surface and sugar palm fiber as the core (E-type board) exhibited good sound absorption properties.

• Journal of the Korean Applied Science and Technology
• /
• v.38 no.1
• /
• pp.300-308
• /
• 2021

In this study, 3D networked poly(sodium acrylate) gel was polymerized and controlled with the crosslinking environment to evaluate the mechanical properties and swelling behavior. In general, as the degree of crosslinking in a pre-gelled solution increases, the swelling ratio of the 3D networked gel decrease while the mechanical strength of the gel increases. Interestingly, this study demonstrates that the polymerization and crosslinking efficiency in gelling process could be depended on the crosslinking environment by evaluating the number of elastically cross-links in 3D networked gel. As a result, the number of elastically corss-links would be changed with 3.6 times as varying of the crosslinking environment while keeping the degree of crosslinking. It is expected that the 3D networked gel would be optimized as an effective absorbing agent for VOCs by using the gel evaluation method based on the number of elastically cross-links.

• Journal of the Korea Furniture Society
• /
• v.19 no.6
• /
• pp.475-486
• /
• 2008

In this study, fire-retardant chemicals were melt with mixed composition ratios of dibasic ammonium phosphate and each half of boric acid and borax in hot water, in which hammer-milled chips were immersed to increase swelling of waste particleboards. Also, fire-retardant treated particles from sawn lumber chip and recycled particleboard chip were composed in ratio of 70:30 in core layer to improve boards' properties. Retention ratio of fire-retardant chemicals for the particles for face layer was high due to high specific surface area, and that of sawn lumber chips was somewhat higher than that of recycled particleboard chips. The mixture of particles from sawn lumber chips and recycled PB of 70:30 in weight ratio exceeded bending strength of 100 $kgf/cm^2$. It seemed that the relatively greater portions of dibasic ammonium phosphate affected adversely to dimensional stability, however fire-retardants treatment resulted in distinct effect lowering formaldehyde emission such as $E_0$ type(0.5mg/$\ell$ or less) in KS F 3104. In fire-retardancy, the recycled boards with a mixed ratio of dibasic ammonium phosphate to boric acid borax(50:50 mixture) of 70% to 30% in weight satisfied fire-retardancy 3rd grade in KS F 2271, and also this composition from cone calorimeter test met same standard grade figuring total heat release of 4.6MJ/$m^2$.

• Journal of the Korean Wood Science and Technology
• /
• v.33 no.6 s.134
• /
• pp.46-54
• /
• 2005

To make the composite panels of wood particles and recycled plastics, the recycled polypropylene was used. In the composite panels the sizes of wood particles were 1/32", 1/4" and 1/2" mesh, and the composition ratios of the recycled plastics were 10%, 30%, 50% and 70%. The physical and mechanical properties of the composite panels were investigated. As the composition ratio of wood particle increases, the density increases, while it decreases at the same composition ratio because the size of wood particle increases. As the composition ratio of recycled polypropylene increases from 10% to 30%, both thickness swelling and water adsorption significantly decrease. As the composition ratio of recycled polypropylene increases, the modulus of rupture in bending strength increases, but the modulus of elasticity in bending strength decreases. SEM shows that the dissolved recycled polypropylene penetrates into tracheid and pit, and bonds mechanically to other wood particle and matrix to increase the bonding strength and improve the physical and mechanical properties of composite panel.

• Ocean Science Journal
• /
• v.43 no.4
• /
• pp.183-193
• /
• 2008

Oncaea venusta Philippi, 1843 has been known as having some different size groups, but recent genetic study for cyt b and ITS 1 (Elvers et al. 2006) suggests that these size groups can be considered as different species. Of these size groups, the largest O. venusta Philippi and the smallest O. venella Farran, 1929 were first described in Korean waters. The latter is easily distinguishable from the former in the following characteristics in addition to its small size: (1) length to width ratio of genital double somite of two genders smaller, and (2) female second pediger bearing inconspicuous dorso-posterior swelling. Oncaea venusta and O. venella co-occur in Korean waters during spring to fall, but their occurrence patterns seasonally differ: the former shows higher density in fall while the latter does in summer.

• Journal of Chest Surgery
• /
• v.17 no.1
• /
• pp.140-143
• /
• 1984

We have experienced 30 patients of tuberculous chest wall abscess which was surgically treated at Kyung Hee University hospital during 6 years from Jan, 1978 to Dec, 1983. We analyze 30 cases of clinical findings and surgically treated, and 20 cases of chest X-rays are available. The results of this sturdy are as follows: 1.Sex ratio ; Male: Female = 1:1.72. 2.Chief complaints are fluctuated mass with or without tenderness or pain and pus from wound. 3.Out of 20 cases of chest x-rays revealed 8 cases of osteolytic lesion, 11 cases of soft tissue swelling, 5 cases of pleural changes and 4 cases of negative findings. 4.We resected partially 43 ribs of 30 patients [average: 1.43 resected] in tuberculous chest wall abscess. 5.Operative methods of tuberculous chest wall abscess were partial resection of destructed or denuded periosteum of ribs and curettage of its surrounding tissues in operative field.

• Journal of Biomedical Engineering Research
• /
• v.10 no.3
• /
• pp.237-242
• /
• 1989

The physical properties and drug release behaviours of polyethylene glycol grafted poly ${\gamma}$- benzyl L-glutamate (PEG- g- PBLG), polyethylene glycol crosslinked poly ${\gamma}$-benzyl L- glutamate(PEG-c-PBLG), and PBLG homopolymer are compared. PBLG containing PEG segements showed higher wettability and larger enlongation than PBLG homoplymer, but lower elastic modulus. The release rate of rhodamine is strongly influenced by the wettability of the polymer. Rhodamine is more rapidly released from PEG-c-PBLG membrane having a larger water contact angle than from other polymer having a lower water contact angle. The surfaces of PBLG derivative membranes are modified by substitution reaction using hydroxyalkylamine. The resulting polymer membranes showed hider wettability and swelling ratio than virgin membranes.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.36 no.1
• /
• pp.10-14
• /
• 2018

A photo-crosslinkable sericin hydrogel has been prepared by introducing methacrylate groups on sericin. Lysine was the amino acid for methacrylation and the degree of methacrylation was increased with the amount of methacrylic anhydride added. When the concentration of methacrylic anhydride was 20% of sericin, 0.635 mmol/g of methacrylate group could be introduced. The storage modulus of sericin hydrogel was increased proportionally with the degree of methacrylation. However, the swelling ratio of sericin hydrogel decreased with the increase of methacrylation.