• Journal of Technologic Dentistry
• /
• v.26 no.1
• /
• pp.49-58
• /
• 2004

Two diketones, 1-phenyl-1,2-propanedione(PD) and 2,3-butanedione (BD) were investigated as new visible light photosensitizers for a dental resin composite of bis-GMA in order to improve photopolymerization effect. And the photopolymerization efficiency of mixed photosensitizers, PD-CQ and DA-CQ, was studied. Photopolymerization effect of photosensitizers were compared with that of camphorquinone(CQ), the most widely used photosensitizer. The photopolymerization efficiency of bis-GMA containing the photosensitizer increased with irradiation time. The increase was in the order: BD < CQ < PD. The photopolymerization efficiency of this mixture was not so efficient as CQ or PD.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.6
• /
• pp.36-44
• /
• 1999

The rapid Tooling technique is classified into two methods: one to directly utilize the model which was made by rapid prototyping technologies for dies, and the other to make a transferred type using the model as a master model and create dies and molds using it. In this study, the Al powder filled resin was made several mixed ratios and meshes sizes, and applied to slurry casting. And, variation of mechanical characteristics such as the shrinkage rate, the tensile strength, the elongation, the hardness, and surface roughness, are measured to compare. Consequently, as higher is the powder mixed ration and as smaller is the grain size of the power, the mechanical characteristics of the final mold are improved. Finally, the metal short fiber which can be fabricated easily and cheaply, if the self-excited vibration of an elastic tool, was also applied to slurry casting. It has been found tat the hardness gets higher, while the shrinkage rate lower, if mixed with short fiber.

• Elastomers and Composites
• /
• v.35 no.3
• /
• pp.196-204
• /
• 2000

SBR, polyurethane, acryl and epoxy latex were separately mixed with ethylene -vinylacetate emulsion(EVA) in the range of $0{\sim}50wt%$. For the mixtures, the various physical properties such as defoamerability, mechanical property, and water resistance were experimentally examined. The excellent defoamer was BYK-021 and the appropriate use of it was 0.3 phr for the total components. The shrinkage of compounds was influenced by the compatability of resins and the formation of voids. The mechanical properties was related to the cohesive force of resin particles, the coagulation of cement particles and the co-bonding of resin particles with cement particles. Mixing latex separately showed better properties then non-mixing in the shrinkage ratio, flexural strength, adhesive strength, and impact strength. The water resistance of composites mixed with cement was worse than that of EVA resin.

• Journal of the Korea Furniture Society
• /
• v.10 no.1
• /
• pp.51-56
• /
• 1999

This research was carried out to investigate the Hanji sludge(black color)-wood fiber and wood particle composited applied by waste sludges arising from the making process of Hanji (Korea paper). In experimental design, four levels of the mixed ratio of Hanji sludge to wood fiber or wood particle(10:90, 20:80, 30:70 and 40:60), three kinds of the resin(PMDI, urea and phenol resin)and three kinds of the specific gravity(0.6, 0.75 and 0.9) were designed to determine the tensile strength of Hanji sludge-wood fiber and wood particle composites. From the results and discussion, it may be concluded as follows: In Hanji sludge-wood fiber and wood particle composites, tensile strengths showed decreasing tendency absolutely by increasing Hanji sludge additive, but clearly increase with the increase of specific gravity. In Hanji sludge-wood fiber composites, there were no differences between PMDI and urea resin-bonded composites, but phenol resin-boned composites were made possibly until the addition of 30% Hanji sludge. On the other hand, Hnji sludge-wood particle composites(SpGr=0.6) have very low tensile strength values. But they were made favorably until the addition of 20% Hanji sludge in Hanji sludge-wood particle composites(SpGr=0.9).

• Korean Journal of Materials Research
• /
• v.30 no.1
• /
• pp.22-30
• /
• 2020

Small fishing vessels are manufactured using FRP. Various studies have been conducted to increase the strength of the composite material by mixing alumina powder with resin. Tensile tests and flexural strength tests are conducted to examine the effect of alumina powder on the strength of GFRP. In the current study, resin/alumina composites at different alumina contents (i.e., 0, 1, 5, and 10 vol%) have been prepared. The physical and mechanical properties of the prepared composites have been investigated. From the results, the tensile strength of the specimen with alumina powder mixed in at 10% shows the highest value of 155.66 MPa. The tensile strength of the specimen mixed with alumina powder increases with the amount of alumina powder impregnated. In the flexural strength test, the flexural strength of neat resin without alumina powder has a highest value of 257.7 MPa. The flexural modulus of ALMix-5 has a highest value of 12.06 GPa. Barcol hardness of ALMix-10 has a highest value of 51. We show that alumina powder leads to decreasing cracks on the surface and decreasing length area of delamination.

• Restorative Dentistry and Endodontics
• /
• v.20 no.1
• /
• pp.97-112
• /
• 1995

The purpose of this study was to evaluate the effect of wetting condition made by drying time on bonding of resin cement to dentin. Freshly extracted bovine teeth were grinded to expose flat dentin surfaces. After the exposed dentin surfaces were treated with pretreatment agents and water rinse, each wetting condition of dentin surfaces was made according to drying times and methods including slight blow bry for I-second by air syringe, blow dry for 20-second by air syringe, and 12-hour dry in desiccator respectively. and then, previously made composite resin specimens were bonded onto each conditioned dentin surface of the specimen using Panavia-21(Kuraray Co.), Bistite(Tokuso Co.), and Choice(use with All bond-2, Bisco Inc.) resin cement according as manufacturer's instruction. Bonded specimens were stored in $37^{\circ}C$ distilled water for 24 hours, then the tensile bond strength was measured, cohesive failure rate was calculated, and fractured dentin surfaces and acrylic rod sides were examined under scanning electron microscope. The result were as follows ; In the group of bonding with Panavia-21 resin cement, higher tensile bond strength was seen in 12-hour dry group than in I-second and 20-second dry group(p<0.01). In the group of bonding with Bistite resin cement, higher tensile bond strength was seen in 1-second dry group than in 20-second and 12-hour dry group(p<0.01). In the group of bonding with Choice resin cement, no significant differences of bond strength under given drying time were seen. Cohesive failure rates derived from the groups of bonding with Panavia-21 and Choice resin cement were increased with the increase of tensile bond strength in each drying time. On SEM examination of fractured surface, adhesive failure mode with fractured resin tags was mostly seen in wet condition with I-second drying time in the group of bonding with Panavia-21 resin cement, mixed failure mode with shortened and fractured resin tag was seen in the group of bonding with Bistite resin cement, and regardless of drying time, and cohesive-adhesive mixed failure mode with fracture of 'Hollow' typed resin tags was mainly seen in the group of bonding with Choice resin cement.

• Journal of the Korean Wood Science and Technology
• /
• v.26 no.1
• /
• pp.97-105
• /
• 1998

This study examined the combined using effects of urea-formaldehyde (UF) resin and emulsifiable methylene diphyenyl diisocyanate (EMDI) resin to overcome performance limit of three-layer particleboards commonly made by UF resin. Two adhesive adding methods were applied with three types of resin combination system to each layer of particleboards. The one was simultaneously spreading method with emulsified compound resin (UF and EMDI) while the other was separately spreading method with unemulsified EMDI resin after UF resin spreading. The performance of particleboards bonded with 2% EMDI resin to the inner layers(IL) were similar to that of controls bonded with 8% UF resin. In the case of the emulsified compound resin application to the all layers of particleboards, there were marked reinforcing effects of EMDI resin, although a small amount of EMDI resin was mixed with UF resin. Especially bending MOR after 24 hours cold water-immersion and thickness swelling after 2 hours hot water-immersion of compound resin-bonded particleboards were remarkably different from those of pure UF resin-bonded particleboards. It was found that separately spreading method with unemulsified EMDI resin was more effective than simultaneously spreading method with emulsified compound resin to sustain the internal bond strength of particleboards after 24 hours cold water-immersion. In the resin combination systems to outer layers/inner layers of particleboards, water resistance and strength properties were superior in order of UF+EMDI/UF+EMDI > UF/UF+EMDI > UF/UF. And water resistance of particleboards was greatly dependent upon EMDI resin level in any adhesive adding method.

• The Journal of Advanced Prosthodontics
• /
• v.9 no.5
• /
• pp.364-370
• /
• 2017

PURPOSE. To explore the influence of different surface conditionings on surface changes and the influence of surface treatments and aging on the bond strengths of composites to non-aged and aged resin nanoceramics. MATERIALS AND METHODS. Rectangular-shaped non-aged and aged (5000 thermocycles) resin nanoceramic specimens (Lava Ultimate) (n=63, each) were divided into 3 groups according to surface treatments (untreated, air abrasion, or silica coating) (n=21). The surface roughness was measured and scanning electron microscopy was used to examine one specimen from each group. Afterwards, the specimens were repaired with a composite resin (Filtek Z550) and half were sent for aging (5000 thermocycles, n=10, each). Shear bond strengths and failure types were evaluated. Roughness and bond strength were investigated by two- and three-way analysis of variance, respectively. The correlation between the roughness and bond strength was investigated by Pearson's correlation test. RESULTS. Surface-treated samples had higher roughness compared with the untreated specimens (P=.000). For the non-aged resin nanoceramic groups, aging was a significant factor for bond strength; for the aged resin nanoceramic groups, surface treatment and aging were significant factors. The failures were mostly adhesive after thermal cycling, except in the non-aged untreated group and the aged air-abraded group, which had mostly mixed failures. Roughness and bond strength were positively correlated (P=.003). CONCLUSION. Surface treatment is not required for the repair of non-aged resin nanoceramic; for the repair of aged resin nanoceramic restorations, air abrasion is recommended.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2005.11b
• /
• pp.214-221
• /
• 2005

Spent ion-exchanged resin generated from various purification systems in CANDU reactor is causing concern due to a limited storage capacity and safe disposal. As a suggestion for a proper treatment technology for the spent ion-exchanged resin containing a high activity of C­14 radionuclide which would be classified as Class A and C wastes, a fundamental study for the development of C-14 removal technology from a spent resin was performed. The adsorption characteristics of the inactive $HCO_3^-$ ion and other ions in a stripping solution on IRN-150 mixed resin was evaluated and the removal technology of the $HCO_3^-$ ion adsorbed on IRN-150 by an alkaline stripping method was proposed.

• Proceedings of the Korean Fiber Society Conference
• /
• 1986.06a
• /
• pp.35-35
• /
• 1986