• Composites Research
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• v.31 no.1
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• pp.30-36
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• 2018

The curing behavior of glass fiber reinforced epoxy prepregs based on Bisphenol-A (BPA) was studied by differential scanning calorimetry (DSC). The total heat of reaction(${\Delta}H_{total}=280.3J/g$) was determined based on the results of the dynamic heating scanning experiments. Isothermal experiments were carried out at $110{\sim}130^{\circ}C$, and it was observed that the maximum conversion and the maximum reaction rate were increased as temperature increased. Also Kamal equation was applied to analyze autocatalytic reaction of epoxy prepregs. The higher temperatures, the greater reaction rate constants ($k_1$, $k_2$). Theoretical values were calculated by these reaction rate constants and compared with experimental values. And it was confirmed that they were in reasonable agreement. At the beginning of the reaction, the experimental data and theoretical prediction were shown the same tendency, but at the end of reaction, the experimental data were smaller than theoretical predicted values due to reaction rates controlled by diffusion.

• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.652-660
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• 2008

For the recycling of rapid-chilled steel slag, the mechanical strengths and physical properties of EVA-polymer modified mortars with the various replacement ratios of rapid-chilled steel slag were investigated. Twenty five specimens of polymer modified mortars were prepared with the five different amounts of EVA-polymer modifier (0, 5, 10, 15, 20 wt%) and rapid-chilled steel slag (0, 25, 50, 75, 100 wt%). For the investigation of the characteristics of polymer modified mortars, the measurements such as water-cement ratio, unit volume weight, air content for fresh mortar and compressive strength, flexural strength, water absorption, hot water resistance, porosity and SEM investigation for curing specimens were conducted. As a results, with an increase in the replacement ratio of rapid-chilled steel slag, water-cement ratios decreased but unit volume weight increased remarkably. With increasing EVA-polymer modifier and the replacement ratio of rapid-chilled steel slag, percent of water absorption decreased but compressive and flexural strengths increased remarkably. By the hot water resistance test, mechanical strengths decreased but total pore volume and porosity increased remarkably. In the SEM observation, the components of specimen were shown to stick to each other in the form of co-matrix phase before hot water resistance test, but polymer modifier of co-matrix phase was decomposed or deteriorated after hot water resistance test.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.119-125
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• 2020

Research on high-attenuation concrete for the vibration reduction performance by mixing epoxy-based synthetic resins and aggregates is actively being conducted. The curing time of high-attenuation concrete is very short because water is not used, and the physical and dynamic properties are very excellent. therefore, it is expected to be widely used in building structures requiring reduction of interior-floor noise and vibration. Furthermore, A way to expand the applicability of the high-damping concrete mixed with polymer in the field of reinforcement material have been variously studied. In order to replace polymer concrete with ordirnary concrete and existing anti-vibration reinforcement material, it is necessary to review overall vibration reduction performance considering physical properties, dynamic properties, productivity and field applicability. In this study, the physical and dynamic properties of polymer concrete by epoxy mixing ratio compared with ordirnary concrete. As a result, the elastic modulus was similar. On the other hand, polymer concrete for the compressive, tensile, and flexural strengths was quite more excellent. In particular, the measured tensile strength of polymer concrete was 4-10 times higher than that of ordirnary concrete. it was a big difference, and the frequency response function and damping ratio was studied through modal test and finite element analysis model. The dynamic stiffness of polymer concrete was 20% greater than that of ordirnary concrete, and the damping ratio of polymer concrete was approximately 3 times more than that of ordirnary concrete.

• Polymer(Korea)
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• v.35 no.2
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• pp.136-140
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• 2011

The plasma resistances of nitrile curable perfluoro elastomer (NT PFE) and peroxide curable PFE (PO PFE) after exposing to $NF_3$ and $O_2$ remote plasmas were investigated by analyzing weight loss and morphology of O-ring made of PFE. The compounds were designed following the typical formulations of O-ring/seal which were applied in semiconductor and LCD production site. They were blended by an open roll mill, and then, O-ring was finally made by hot press molding and oven curing. The weight loss was calculated and morphology was observed for each atmosphere and temperature by a digital weighing machine and SEM. As results, it was confirmed the weight loss and related morphology were meaningfully different according to the cure type of PFE, filler system, and the species of remote plasma.

• Polymer(Korea)
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• v.37 no.1
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• pp.121-126
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• 2013

UV-curable high refractive index di-functional epoxy acrylate, 4,4'-thiodibenzenethiol diglycidyl ether diacrylate, was synthesized from acrylic acid and 4,4'-thiodibenzenethiol diglycidyl ether that was obtained by reacting 4,4'-thiodibenzenethiol and epichlorohydrin using a direct method (Taffy process). Its chemical structure was identified by $^1H$ NMR and FTIR. After its dilution with a reactive diluent, 2-phenoxythiol ethyl acrylate as 5, 10, 15, 20, and 30 wt% content, the relationship between their viscosity and refractive index was investigated. Their degree of cure decreased with increasing the amount of reactive diluent, and the refractive index of UV-cured film increased with increasing the degree of cure.

• Polymer(Korea)
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• v.35 no.4
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• pp.342-349
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• 2011

The effect of the amount of vinyltriethoxysilane (VTEOS) in precipitated silica filled silicone rubbers was extensively investigated in terms of the change of mechanical properties, heat resistance, oil resistance, compression set, resilience, and curing characteristics. As the content of VTEOS increased from 0 to 2.0 phr, the hardness of the silicone rubber increased, however, tensile strength, elongation at break, and tear strength decreased. From heat resistance test, the change of mechanical properties was pronounced for silicone rubber treated with more VTOES. The best heat resistance was achieved at 2.0 phr VTOES. In addition, oil resistance was proportionally improved with VTEOS content. From oil resistance test. it was found that the decrease in hardness and maximum elongation was reduced for VTEOS-added systems. Finally, resilience, compression set, degree of cure and crosslink density were significantly enhanced with the amount of VTEOS.

• Clean Technology
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• v.16 no.4
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• pp.245-253
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• 2010

Optimum conditions for UV-radiated photopolymerization of unsaturated polyester that could be used as protecting layer of large diameter pipe were investigated in this paper. UV photopolymerization method was selected to solve the problems, arising when thermal polymerization by organic peroxide was used, such as the instability of peroxide initiator, the evolution of volatile organic compound, and thermal deformation of product. Two of the photo-initiators (Irgacure 819 and Darocure 1173) well known for its penetrating ability deep into the polymer layer were selected, and the optimum conditions for photopolymerization (1.5 phr initiator content, 1:1.2 initiator ratio, Ga lamp for UV source) were found from the thermal and mechanical test results of the resultant UP polymers. In addition, composite materials containing UP polymer and glass fiber were tested for hardness, impact strength, and flexural strength to find that the impact strength of composite significantly improved.

• Journal of Adhesion and Interface
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• v.7 no.1
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• pp.16-22
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• 2006

In this work, the effect of cure temperature and time on the thermal stability and the exothermic cure reaction peak of a waterborne resol-type phenol-formaldehyde resin, which may be used for preparing phenolic sheet molding compounds (SMC), has been investigated using a thermogravimetric analyzer and a differential scanning calorimeter. The weight loss of waterborne phenol-formaldehyde resin was mainly occurred at three temperature stages: near $200^{\circ}C,\;400^{\circ}C$, and $500^{\circ}C$. The carbon yield at $750^{\circ}C$ for the cured resin was about 62%~65%. Their thermal stability increased with increasing cure temperature and time. Upon cure, the exothermic reaction was taken placed in the range of $120^{\circ}C{\sim}190^{\circ}C$ and the maximum peak was found in between $165^{\circ}C$ and $170^{\circ}C$. The shape and the maximum of the exothermic curves depended on the given cure temperature and time. To remove $H_2O$ and volatile components, the uncured resin needed a heat-treatment at $100^{\circ}C$ for 60 min at least prior to cure or molding. Curing at $130^{\circ}C$ for 120 min made the exothermic peak of waterborne phenol-formaldehyde resin completely disappeared. And, post-curing at $180^{\circ}C$ for 60 min further improved the thermal stability of the cured resin.

• Journal of the Korean Chemical Society
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• v.10 no.4
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• pp.166-174
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• 1966

The multistep mechanism of photosensitized curing reaction cinnamoylated photosensitive polymer is proposed from the energy level diagram of cinnamic acid and sensitizer, and from the fact that excess of sensitizer brings the sensitivity to a limiting value etc. Various factors which have effects on the ability of sensitizer are also discussed. The mechanism involves following steps: activation to the first excited singlet states of cinnamoyl group(C) and sensitizer(S) by their absorption of photon, their intersystem crossing to the lowest triplet state, bimolecular internal quenching by formation of excimer of sensitizer, triplet excitation energy transfer and intermolecular addition between cinnamoyl group in ground state and that in triplet state. The rate equation derived from this mechanism is $-\frac{d[C]}{dt} = \frac{K_1[C]}{K_2 + [C]}[\frac{I^c_{abs}}{K_3 + [S]} + \frac{K_4[C]}{(K_5 + [C])(K_6 + [S])}(I^s_{abs} + \frac{K_7I^c_{abs}[S]}{K_8 + [S]})]$ where $I^c_{abs}\;and\;I^s_{abs}$: the rates of absorption of photon by cinnamoyl group and sensitizer $K_n$: Constants. It is proved with the cinnamate of poly(glyceryl phthalate)(PGC) in the absence of sensitizer using the infrared analytical method and successfully applied for the experimental data reported on the effects of the degree of cinnamoyl esterification and the concentration of sensitizer upon the sensitivity.

• Polymer(Korea)
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• v.28 no.5
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• pp.426-432
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• 2004

To reduce volumetric shrinkage of the commercially available polymeric dental composite during curing reaction, (2,2-bis [4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane) (bis -GMA) derivatives, i.e., (2,2-bis[3-methyl, 4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propan) (DMBis-GMA) and (2,2-his [3,5-dimethyl ,4- (2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane) (TMBis-GMA) were synthesized and then new dental composite resin composed of Bis-GMA derivatives, diluent, spiro orthocarbonate (SOC), and inorganic filler was produced. Among the Bis-GMA derivative/Bis-GMA derivative/diluent mixtures, Bis-GMA/ TMBis-GMA/TEGDMA mixture exhibited the lowest volumetric shrinkage. Volumetric shrinkage of this mixture was further reduced by adding SOC. Volumtric shrinkage of dental composite prepared from commercially available resin monomer mixture was $2.5\%$, while that prepared from resin monomer mixture having minimum volumetric shrinkage was reduced to $0.7\%$. Mechanical strength of this dental composite was nearly the same with that of commercial products but the time required for the curing reaction was retarded.