• The Journal of Korean Academy of Prosthodontics
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• v.35 no.2
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• pp.330-343
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• 1997

Extraoral maxillofacial prostheses are essential for restoring facial structures that are lost as a result of congenital missing, injuries from accidents, surgical treatments of head and neck cancer. Recently, silicone is the most useful material for this purpose and is more advantageous than other maxillofacial prosthetic materials. However, there are some problems for long-term usage of silicone prostheses due to tear and color change. These are major contributing environmental factors to those problems that are such as ultraviolet light, cleansing agents, changes in humidity and successive adhesion and removal. The aim of this study is to evaluate the physical properties and color changes of maxillofacial prosthetic silicone material by those environmental factors using A-2186 silicone material (Factor II, USA) and two pigments, cadmium yellow medium and cosmetic red. Aluminium molds were fabricated according to the ASTM No. D412 & D624 specifications and resulted specimens from molds were fabicated and treated as follows. Control group and experimental I group were fabricated with 0.1% wt. pigment mixing in silicone elastomer and II-1 group, II-2 group of experimental II group were fabricated with 0.2%, 0.3% wt. pigment mixing in silicone elastomer, respectively. Control group was kept in darkroom at room temperature, I-1 group was kept under natural sunlight during 1week, I-2 group was soaked in 20% soap water during 1wk. I-3 group was successively adhered and removed 200 times on inner region of arm using Daro adhesive-33. Experimental II groups were kept in darkroom at room temperature. Instron universal testing machine was used to measure the % elongation, tensile strength, tear strength of control, experimental I, II groups and reflectance spectrophotometer(COLOR EYE-3000, Macbeth, USA) was used to measure the color differences between control group and experimental I group. The results were as follows : 1. When compared with control group, natural weathering group and 20% soap-water soaking group had no significant differences in % elongation(p>0.05). 2. 200 times successive adhesion and removal group, 0.2% wt. pigment group and 0.3% wt. pigment group had significant decreases in % elongation(p<0.05). 3. Natural weathering group, 20% soap-water soaking group and 200 times successive adhesion and removal group had no significant differences in tensile strength (p>0.05). 4. 0.2%, 0.3% wt. pigment groups had significant decreases in tensile strength(p<0.05). 5. Values of all experimental groups were decreased in tear strength. and 200 times successive adhesion and removal group had significant decrease in tear strength(p<0.05). 6. Natural weathering group and 20% soap-water soaking group had significant color differences(${\Delta}E$) and it could be detectable to naked eye(p<0.05). 7. Color differences between control group and 200 times adhesion and removal group were not detectable to the naked eye (${\Delta}E<1.0$).

• Journal of Trauma and Injury
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• v.28 no.1
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• pp.21-26
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• 2015

Complete radial tears of the lateral meniscus are relatively rare. Once torn, the injury can be debilitating due to disruption of the circumferential fibers of the meniscus. We experienced a case of a lateral meniscus with a complete radial tear at the midbody, where the two torn ends were displaced more than 1 cm and could not be approximated during arthroscopy. Thirteen months after surgery, follow-up MRI and second-look arthroscopic findings showed that the complete radial tear has healed spontaneously. However, twenty nine months after the second-look arthroscopy, the patient complained of severe knee pain during exercise. On follow-up MRI, increased sclerosis and newly developed bone marrow edema were observed in the lateral femoral condyle, compared with previous MR images. Finally, we performed meniscal allograft transplantation due to the defective properties of the completely healed lateral meniscus.

• Journal of Adhesion and Interface
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• v.9 no.2
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• pp.24-31
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• 2008

In this work, calcium hydroxide and magnesium carbonate as metal ionic crosslinking agents were used to introduce ionic crosslinking points to the ethylene vinylacetate (EVA) emulsions for the enhancement of water resistance and mechanical properties of emulsion films. The properties of EVA emulsion film were investigated in crosslinking density, thermal features, surface energy, and mechanical properties, such as tensile strength, elongation at break and tear strength. With the increasing content of metal ionic crosslinking agent, the crosslinking density of the EVA emulsion film increases, resulting into the improvement of water resistance. The surface energy and mechanical properties of the EVA emulsion film, however, showed somewhat different behaviors. The highest surface energy, tensile strength, and tear strength were observed when 0.4% for calcium hydroxide and 0.5% for magnesium carbonate was added respectively, because the EVA emulsion containing carboxylic acid forms strong carboxylate-metal bond of ionically-crosslinked system. Therefore, it can be concluded that metal ionic crosslinking agents, such as magnesium carbonate and calcium hydroxide are considered to improve water resistance and mechanical properties of the EVA emulsion.

• Journal of the Korean Wood Science and Technology
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• v.48 no.5
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• pp.581-590
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• 2020

Pulp refining is the major way to alter the properties of fibers and formed paper. Different combinations of the bar profile of the rotor and stator during low consistency refining processes directly affect the properties of the paper. In this study, a mixture of softwood and hardwood pulp was refined by varying the bar angle of the stator while that of the rotor is fixed at 0º. The pulp samples were collected at different refining times. Then, the pulp and paper properties, such as beating degree, fiber external fibrillation, and tensile and tear indexes were measured to explore the effects of the combined refining plates at different bar angles on paper properties. The results of the experiment show that the combined refining plate of 0º and 5º recorded the most significant improvement in the pulp beating degree and fiber external fibrillation. This consequently increased the fiber bonding area, which in turn, improved both the tensile and the tear indexes of the paper. Also, the influence of the combined refining plates with a larger bar angle on the paper properties was weaker compared to that of smaller angles. This study not only provides ideas for the bar profile design but also improves the optimal selection of refining plates.

• Polymer(Korea)
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• v.28 no.2
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• pp.185-193
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• 2004

Elastomeric nanocomposites were prepared by employing zinc dimethacrylate into an acrylonitrile-butadiene rubber, and their network structures, mechanical properties, and fracture morphologies were investigated according to the adding methods and contents of zinc dimethacrylate. The total crosslink density increased with increasing the zinc dimethacrylate level, due to increased ionic bonds. Both the tensile strength and tear strength increased with increasing zinc dimethacrylate loadings, and then decreased after reaching a maximum value. It was found that the tear strength and crack resistance were greatly affected by the mixing method of zinc dimethacrylate. The in-situ nanocomposites, where zinc dimethacrylate particles were formed by the reaction of zinc oxide and methacrylic acid, showed much improved tear strength and crack resistance compared to those of the nanocomposites based on the direct mixing of zinc dimetacrylate powders. This was because of the finer zinc dimethacrylate particles and improved dispersion of the in-situ nanocomposites.

• Journal of Forest and Environmental Science
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• v.14 no.1
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• pp.89-100
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• 1998

The study was carried to investigate the change of internal stress and physical properties of paper by the mutiplying of paper structuring that is an useful means to maximize the performance and use of the fiber raw material. The effects of recycled fiber on the physical properties of multiplied paper also were studied. The beating increased the internal stress of single layered paper, while filler loading decreased the internal stress. Multiplying the structure of paper decreased the internal stress and the most of physical properties except for tear index. It was found that the properties of paper could be changed by the pulp type, beating and the combination of raw materials. The introduction of filler in the middle and/or outer layer could improved the internal stress, tensile index, tear index and burst index. The addition of recycled fiber increased the opacity and stiffness of paper in both single layered and multiplied paper. Multiplying the structure of paper improved the air permeability and stiffness, while decreased burst index.

• Textile Coloration and Finishing
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• v.24 no.3
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• pp.221-231
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• 2012

Rayon fabrics were treated with some commercial non-formaldehyde and low-formaldehyde resins, and then their effect on the physicochemical properties of fabrics, including formaldehyde release, tear strength, shrinkage, and wrinkle recovery, were investigated respectively. Rayons treated with non-formaldehyde resin, little formaldehyde release was observed. Considering other factors, the optimal concentration of non-formaldehyde resin was shown to be 11-13%, and curing temperature was $170{\sim}175^{\circ}C$. In case of low-formaldehyde type, 9-11% resin concentration and curing temperature of $170{\sim}180^{\circ}C$ were recommended for optimal finishing condition. The choice and combination of resins and catalysts were also important factors, and preliminary considerations before resin-finishing of rayon are also important to get much better results.

• The Journal of Advanced Prosthodontics
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• v.8 no.5
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• pp.372-379
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• 2016

PURPOSE. Alginate mixers available in the market do not have the automatic proportioning unit. In this study, an automatic proportioning unit for the alginate mixer and controller software were designed and produced for a new automatic proportioning unit. With this device, it was ensured that proportioning operation could arrange weight-based alginate impression materials. MATERIALS AND METHODS. The variation of coefficient in the tested groups was compared with the manual proportioning. Compression tension and tear tests were conducted to determine the mechanical properties of alginate impression materials. The experimental data were statistically analyzed using one way ANOVA and Tukey test at the 0.05 level of significance. RESULTS. No statistically significant differences in modulus of elastisity (P>0.3), tensional/compresional strength (P>0.3), resilience (P>0.2), strain in failure (P>0.4), and tear energy (P>0.7) of alginate impression materials were seen. However, a decrease in the standard deviation of tested groups was observed when the customized machine was used. To verify the efficiency of the system, powder and powder/water mixing were weighed and significant decrease was observed. CONCLUSION. It was possible to obtain more mechanically stable alginate impression materials by using the custom-made proportioning unit.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.931-934
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• 2008

Polyurethane apply to the waterproof widely. Polyurethane rubbers are prepared that the influences of a thermal aging on the properties are investigated. Polyol and Polyisocyanate were varied ratio in the range mixed by using individual product that was vulcanized by a hot. The waterproofs of Polyurethane were investigated about tensile strength, tear strength and elongation after the thermal Aging for 168, 336, 504 hrs at 70$^{\circ}$C and 80$^{\circ}$C in the air oven. As the increase of the thermal aging time, tensile strength, tear strength and elongation were reduced.

• Textile Coloration and Finishing
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• v.24 no.2
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• pp.121-130
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• 2012

Cotton fabrics were treated with some commercial non-formaldehyde and low-formaldehyde resins, and then their effect on the physicochemical properties were respectively investigated including formaldehyde release, tear strength, shrinkage, and wrinkle recovery. Formaldehyde release less than 10ppm was obtained only by non-formaldehyde resin. Considering other factors, the optimal concentration of non-formaldehyde resin was shown to be 9-11%. In case of low-formaldehyde type, 5-7% resin concentration and curing temperature of $160{\sim}170^{\circ}C$ were recommended for optimal finishing condition. The choice and combination of resins and catalysts were also important factors, and preliminary considerations before treating cotton fabrics with resins used in this study are also important to get much better results.