• Journal of the Korean Applied Science and Technology
• /
• v.16 no.2
• /
• pp.171-177
• /
• 1999

The objectives of this study is to investigate the optimum reaction conditions and to identify the product formula in the synthesis of a silicone/acrylic resin that curing in moisture at room temperature. By the addition polymerization of monomers, n-butyl acrylate, methyl methacrylate, n-butyl methacrylate, and 3-methacryloxypropyltrimethoxysilane. a quarter polymer was obtained. Among various initiators investigated in this study, 2.2'-azobisisobutyronitrille was found to be the most suitable initiator. The optimum reaction conditions found in this study are 70 wt% of initial solvent amount, 120 minutes of dropping time, 3 times of initiator addition, $82{\sim}105^{\circ}C$ of reaction temperature, and 8 hrs of reaction time. Also, number average molecular weight of $11700{\sim}33100$ and molecular weight distribution of $1.81{\sim}3.44$ were obtained.

• Restorative Dentistry and Endodontics
• /
• v.24 no.1
• /
• pp.26-39
• /
• 1999

Bis-GMA, the representative monomer of bonding resin, contributes to the rigidity of bonding layer. Hydrophilic monomer contributes to the permeability into dentin substrates while weaken the bonding layer due to its small molecular weight. The degree of conversion also contributes to the ultimate strength of the bonding layer. This study was performed for the correlation analysis of monomer ratio and dentin bonding strength via degree of conversion. 7 experimental bonding resins were prepared with Bis-GMA, ratio from 20% to 80% by 10% increment, and hydrophilic HEMA monomer. Their degree of conversion and shear bond strength to dentin were compared with Scotchbond Multi-Purpose adhesive, and the fractured surfaces were examined microscopically. The results were as follows; 1. The degree of conversion increased when, the ratio of Bis-GMA increased from 20% to 70%, whereas it decreased when the ratio of Bis-GMA was 80%. 2. Shear bond strengths of the experimental bonding resins of 80%, 70%, 60% ratio of Bis-GMA were significantly higher than those of the experimental bonding resin of 50% ratio of Bis-GMA and Scotchbond Multi-Purpose adhesive. Lower shear bond strengths were obtained with the experimental bonding resins of 40%, 30%, 20% ratio of Bis-GMA (p<0.05). 3. Adhesive fractures were associated with the bonding resins of the lower bond strength, while cohesive fractures within the bonding resin layer were associated with the bonding resins of higher bond strength. Bonding resins with shear bond strength higher than 18MPa showed some cohesive fractures within the composite resin or within the dentin. 4. Correlations between Bis-GMA ratio and the degree of conversion (r=0.826), between Bis-GMA ratio and shear bond strength (r=0.853), and between the degree of conversion and shear bond strength (r=0.786) were significant (p<0.05).

• Polymer(Korea)
• /
• v.25 no.2
• /
• pp.246-253
• /
• 2001

Amino terminated PES-CTBN-PES triblock copolymer was synthesized from PES oligomer and commercial CTBN rubber (CTBN1300$\times$13), and molecular weight of the copolymer was controlled to be 15000 g/mole. The copolymer was utilized to toughen diglycidyl ether of bisphenol-A (DGEBA) epoxy resin which was cured with 4,4'-diaminodi-phenylsulfone (DDS) and subjected to the measurement of thermal properties, fracture toughness ( $K_{IC}$), flexural properties and solvent resistance. The properties were compared with those from the samples modified by CTBN/PES blends. The maximum loading of copolymer into the epoxy resin was 40 wt% without utilizing solvent, at which $K_{IC}$ fracture toughness of 2.21 MPa${\cdot}m^{0.5}$ was obtained without sacrificing flexural properties and chemical resistance. However, the epoxy resin modified with PES/CTBN blend exhibited much lower $K_{IC}$ and flexural properties compared to the epoxy resins toughened by PES-CTBN-PES copolymers.

• Tribology and Lubricants
• /
• v.14 no.4
• /
• pp.72-78
• /
• 1998

In this work, the effects of binder materials on the tribological behavior were experimentally evaluated for air curable MoS$_2$bonded film lubricants. The binders tested were basically alkyd and acryl based resins, and also were modified by nitro-cellulose in various weight percentages. Effects on the binder ratio to solid lubricants and the molecular weight of binders were also investigated in all aspects of the tribological behavior. For the tests, LFW-1 and Falex tester were used to measure mainly the endurance life and load carrying capacity of bonded lubricants. Results showed that lubricants of methacrylic resin has the better performance than those of other resins, and also the properties of lubricants both of alkyd and acrylic resins could be improved by modification with nitro-cellulose. It was also shown that the optimum ratio of nitro-cellulose related closely to the binder material and the testing machine.

• Korean Chemical Engineering Research
• /
• v.58 no.4
• /
• pp.618-623
• /
• 2020

Spherical phenolic resin beads were synthesized by suspension polymerization at 98 ℃ from phenol, ortho-cresol, formaldehyde, with triethylamine as a basic catalyst, and spherical phenol-cresol copolymer resin beads with relatively low crosslinking density as well. Phenol reacts with formaldehyde at two ortho- and one para- positions to form a crosslinked structure, but ortho-cresol instead of phenol reduces the crosslinking density during copolymerization due to the methyl group at a ortho- position. As a result, spherical phenol-cresol copolymer beads showed more shrinkage with decreasing apparent density compared to the spherical phenol beads when carbonized at 700 ℃ under nitrogen. As the molecular weight of the cresol oligomer increases, the pore radius of the carbonized copolymer beads decreases, which is consistent with the density and shrinkage results. It was confirmed that the characteristics such as density decrease, shrinkage, yield and so on during carbonization can be controlled by controlling the degree of crosslinking of the spherical phenolic resin particles with cresol.

• Journal of the Korean Wood Science and Technology
• /
• v.36 no.5
• /
• pp.42-48
• /
• 2008

This study was conducted to discuss the effects of hardener and extender contents on peak temperature, reaction enthalpy (${\Delta}H$), gelation time, viscosity change, and pH value in three types of UMF (urea-melamine- formaldehyde) resin with the help of perpHecT LogR meter, differential scanning calorimetry (DSC), and advanced rheometric expansion system (ARES), The results indicated that the pH value of Control A steeply decreased to 5,2 in the early stage but relatively remained constant thereafter as in Synthesis 1 and Synthesis 2, The peak temperature and time decreased as well, whereas ${\Delta}H$ and viscosity increased with the increase of hardener content. On the other hand, ${\Delta}H$ was not changed up to the extender content of 5% and then decreased with its further addition, And the pH value and peak temperature showed no change with the increase of extender content at the hardener content of 5% in three types of UMF resin, The effect of hardener content in this experiment, however, appeared more conspicuous in Control A than in the other two types of Synthesis 1 and Synthesis 2, These results might be caused by higher molecular weight with longer chains of methylene ($-CH_2-$) and methylene ($-CH_2-O-CH_2-$) ether bridges or much more branched chains in Control A.

• Journal of dental hygiene science
• /
• v.10 no.6
• /
• pp.445-450
• /
• 2010

The aim of this study was to evaluate the effect according to the fiber type and combination on the reinforcement of heat-polymerized denture base resin. The heat-polymerized resin(Vertex RS, Dentimax, Netherlands) was used in this study. Glass fiber(GL; ER 270FW, Hankuk Fiber Glass, Korea), polyaromatic polyamide fiber(PA; aramid; Kevlar-49, Dupont, U.S.A.) and ultra high molecular weight polyethylene fiber(PE, polyethylene; P.E, Dong Yang Rope, Korea) were used to reinforce the denture base resin specimens. The final size of test specimen was $64mm{\times}10mm{\times}3.3mm$. The specimens of each group were stored in distilled water at $37^{\circ}C$ for 50 hours before measurement. The flexural strength and flexural modulus were measured by an universal testing machine(Z020, Zwick, Germany) at a crosshead speed of 5 mm/min in a three-point bending mode. In this study, all fibers showed reinforcing effects on denture base resin(p<0.05). In terms of flexural strength and flexural modulus, glass fiber 5.3 vol.% showed most effective reinforcing effect on heat polymerized denture base resin. For flexural modulus, PA/GL was the highest in denture base resin specimen for hybrid FRC using two combination (p<0.05). Glass fiber 5.3 vol.% and PA/GL are considered to be applied effectively in reinforcing the heat polymerized denture base resin.

• Macromolecular Research
• /
• v.11 no.6
• /
• pp.444-450
• /
• 2003

Hydrophobically End-capped polyethylene oxide Urethane Resin(HEUR)-associating polymers, HEUR 35(8), HEUR 35(12), and HEUR 35(18), comprise a polyethylene oxide (PEO) having a molecular weight of 35,000 that is end capped with two C$\_$8/H$\_$17/, C$\_$12/H$\_$25/, and C$\_$18/H$\_$37/ alkyl chains, respectively. These associating polymers were synthesized by condensation reactions with polyethylene oxides and alkyl isocyanates. The self-diffusion coefficients of HEUR-associating polymers were measured in aqueous solution by pulsed-gradient spin-echo (PGSE) nuclear magnetic resonance (NMR) spectroscopy. All polymers underwent a decrease in their mean diffusion coefficients as the concentration was increased. However, the dispersion of the diffusion coefficients, ${\beta}$, about the mean fluctuated with changes in concentration. The large dispersion at low concentrations of HEUR 35(8) and HEUR 35(12) is related to the interaction between hydrophobic end groups, and the large dispersion at high concentrations of HEUR 35(18) is correlated with transient network formation. These results are valuable for predicting the associating mechanism of the large aggregates before and after their critical micelle concentration.

• Polymer(Korea)
• /
• v.35 no.3
• /
• pp.196-202
• /
• 2011

The cure kinetics of a bisphenol A epoxy resin and polyoxypropylene diamine curing agent system are investigated in both dynamic and isothermal conditions by differential scanning calorimetry (DSC). In dynamic experiments, the shift of exothermic peaks obtained at different heating rates is used to obtain activation energy of overall cure reaction based on the methods of Ozawa and Kissinger. Isothermal DSC data at different temperatures are fitted to an autocatalytic Kamal kinetic model. The kinetic model is in a good agreement with the experimental data in the initial stage of cure. A diffusion effect is incorporated to describe the later stage of cure, predicting the cure kinetics over the whole range of curing process. Also, dynamic mechanical analysis is performed to evaluate the storage modulus and average molecular weight between crosslinkages.

• Journal of the Korea Convergence Society
• /
• v.9 no.12
• /
• pp.99-106
• /
• 2018

The modifier proposed in this research is for enhancing the affinity of the glass component with the high polymer resin and the molecular weight. The particle packing, tensile strength and shielding performance of the shielding sheet made of the tungsten oxide were evaluated. The best effect can be obtained when 20% of the modifier PMMA used to improve the shielding performance and maintain the affinity and strength with the sealant is mixed. The fusion of the materials presented in this study and the mass production of the shielding sheet through the modifier are possible and will contribute to the production of lightweight shielding sheets in the future.