• Macromolecular Research
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• v.17 no.8
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• pp.585-590
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• 2009

The cure behaviors, dielectric characteristics and fracture toughness of diglycidylether of bisphenol-A (DGEBA)/poly(ethylene terephthalate) (PET) blend system were investigated. The degree of conversion for the DGEBA/PET blend system was measured using Fourier transform infrared (FTIR) spectroscopy. The cure kinetics were investigated by measuring the cure activation energies ($E_a$) with dynamic differential scanning calorimetry (DSC). The dielectric characteristic was examined by dielectric analysis (DEA). The mechanical properties were investigated by measuring the critical stress intensity factor ($K_{IC}$), critical strain energy release rate ($G_{IC}$), and impact strength test. As a result, DGEBAIPET was successfully blended. The Ea of the blend system was increased with increasing PET content to a maximum at 10 phr PET. The dielectric constant was decreased with increasing PET content. The mechanical properties of the blend system were also superior to those of the neat DGEBA. These results were attributed to the increased cross-linking density of the blend system, resulting from the interaction between the epoxy group of DGEBA and the carboxyl group of PET.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.219-223
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• 2001

The on-line cure monitoring during the cure process of composite materials is important for better quality and productivity. The dielectric sensor for cure monitoring consists of base film and electrodes. Because the characteristic of dielectric sensor for the on-line cure monitoring is dependent on the base material, width and number of electrode, etc, the dielectric sensor should be standardized. And the selection of base film material of sensor is very important. In order to prevent the measuring errors generated from the increase of environmental temperature, the base film material should have stable dielectric constant with respect to environmental temperature. In this study, the newly developed dielectric sensor for cure monitoring was designed and the dissipation factor which is function of degree of cure was measured using the sensor. The relationship between the dissipation factor and degree of cure with respect to environmental temperature was investigated.

• Elastomers and Composites
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• v.53 no.3
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• pp.168-174
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• 2018

Natural rubber (NR) and bromo-isobutylene-isoprene rubber (BIIR) were compounded with other formulation chemicals through polymer blending via a mechanical mixing method. After rubber vulcanization by hot-press compression molding, the cure characteristics, mechanical properties, and ozone resistance of the NR/BIIR blends were measured. As the BIIR content increased, the maximum torque of the blends decreased, while the optimum cure time and scorch time tended to increase. Furthermore, the hardness of the blends increased with increasing BIIR content, reaching the maximum value at 75 wt% BIIR, and decreased with a further increase in the BIIR loading. The tensile strength and elongation at break decreased with an increase in the BIIR content, reaching the minimum value at 75 wt% BIIR, and increased with a further increase in the BIIR content. In the ozone resistance test, cracks were not generated when the BIIR content was more than 75 wt%.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.238-244
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• 2000

FBGs have been extensively used as strain sensors or temperature sensors in a variety of applications related to composites because of embedding ability, small size and multiplexing capability. We inspected embedding environments inside composites with optical fiber by microscope analysis and birefringence characteristics of FBG embedded into textile composite laminate by cure monitoring using a high power WSFL. The cure monitoring of the cases with the striped FBG and the recoated FBG provided comprehensive understandings about the birefringence effect induced by the transverse stress. And these results allowed to consider a recoating method as an important tool to relieve birefringence.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.244-249
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• 2001

In this paper, we present the simultaneous measurement of the fabricaition strain and temperature during and after cure of unsymmetric composite laminate uising fiber optic sensors. Fiber Bragg grating/extrinsic Fabry-Perot interferometric (FBG/EFPl) hybrid sensors are used to measure those measurands. The characteristic matrix of sensor is analytically derived and measurements can be done without sensor calibration. A wavelength-swept fiber laser is utilized as a light source. FBG/EFPI sensors are embedded in a graphite/epoxy unsymmetric cross-ply composite laminate at different direction and different location. We perform the real time measurement of fabrication strains and temperatures at two points of the composite laminate during cure process in an autoclave. Also, the thermal strains and temperatures of the fabricated laminate are measured in thermal chamber. Through these experiments, we can provide a basis for the efficient smart processing of composite and know the thermal behavior of unsymmetric cross-ply composite laminate.

• Design & Manufacturing
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• v.7 no.1
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• pp.60-63
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• 2013

Recently, Silicone that one of the thermo-sets is used to making optical products such as LED lenses because of excellent thermal properties. LED lenses are required to keep the precise dimensions, so they must be molded to have the minimum deformation. Thermo-sets have the expansion characteristic on the part of thermal property, it is important to optimize the cure condition so that the deformation of the part become minimum. In this study, to investigate the relationship between the shrinkage by the curing and expansion by the thermal properties of the resin, reactive injection experiment was performed by setting the variables such as mold setting temperature, cure time. As a result, it was confirmed that there was a interval while the thermal properties were transferred to more active during the cure process. It is expected to help in determining the reactive injection molding conditions of the thermo-set parts as well as LED lens in order to reduce the amount of deformation.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.34-37
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• 2000

The effect of novel N-crotyl-N,N-dimethyl-4-methylanilinium hexafluroantimonate (CMH) curing agent on cure behavior and thermal properties of DGEBA epoxy cationic system was investigated. From DSC measurements of DGEBA/CMH system, it was shown that this system exhibits an excellent thermal latent characteristic in a given temperature and reveals complex cure behavior as indicated by multiple exotherms. The conversion and conversion rate of DGEBA/CMH system increased with increasing the concentration of initiator due to high activity of CMH. Viscoelastic properties during gel formation of DGEBA with CMH were investigated by rheological techniques under isothermal condition. The gel time obtained from the modulus crossover. point t(G')=G", was affected by high curing temperature and concentration of CMH, resulting in high degree of network formation in cationic polymerization. The thermal stabilities were discussed in terms of the activation energy for decomposition and thermal factors determined from TGA measurements.ents.

• Polymer(Korea)
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• v.24 no.1
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• pp.105-112
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• 2000

Using a commercial epoxy/carbon fiber composite prepreg (DMS 2224) as a model system, the cure kinetics of vitrifying thermoset system were analyzed by isothermal and dynamic-heating experiments. Focusing on the processing condition of high performance composite systems, a phenomenological kinetic model was developed by using differential scanning calorimetry (DSC) and reaction kinetics theories. The model system exhibited a limited degree of cure as a function of isothermal temperature seemingly due to the diffusion-controlled reaction rates. The diffusion-controlled cure reaction was incorporated in the development of the kinetic model, and the model parameters were determined from isothermal experiments. The first order reaction was confirmed from the characteristic shape of isothermal cure thermograms, and the activation energy wes 78.43 kJ/mol. Finally, the proposed model was used to predict a complex autoclave thermal condition, which was composed of several isothermal and dynamic-heating stages.

• Macromolecular Research
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• v.12 no.3
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• pp.282-289
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• 2004

We have extensively characterized the fluorescence behavior of unsaturated polyester (UP) resin in the absence and presence of a 1,3-bis-(l-pyrenyl)propane (BPP) fluorescent probe at various dynamic and isothermal cure histories by means of a steady-state fluorescence technique using a front-face illumination equipment. In addition, we explored the effect of the fluorescence intensity on the relaxation of the fluorescent probe in the UP resin by resting the dynamically and isothermally cured resin at ambient temperature and pressure for 24 h. The monomer fluorescence intensity, which has two characteristic peaks at 376 and 396nm, changed noticeably depending on the cure temperature and time and provided important information with respect to the molecular and photophysical responses upon curing. The result of the fluorescence study indicates that the increased local viscosity and restricted molecular mobility of the UP resin surrounding the BPP probe after curing are both responsible for the enhancement of the monomer fluorescence intensity. Our results also demonstrate that once the BPP probe has enough time to rearrange and become isolated prior to fluorescence, a sufficient amount of fluorescence is emitted. Therefore, we note that the fluorescence behavior of this UP resin system is influenced strongly by the relaxation process of the fluorescent probe in the resin as well as process used to cure the resin.

• Carbon letters
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• v.27
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• pp.72-80
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• 2018

In the present work, a comparative study of the mechanical behavior of two series of elastomeric composites, based on carboxylated styrene butadiene rubber (X-SBR) and reinforced with rice bran carbon (RBC) and graphite, is reported. Hybrid composites of X-SBR filled with RBC-graphite were also investigated in terms of the cure characteristics, hardness, tensile properties, abrasion resistance, and swelling. It was observed that the cure times decreased with the incorporation of a carbon filler whereas the torque difference, tensile strength, tensile modulus, hardness, and swelling resistance increased compared to the neat X-SBR revealing a favorable characteristic of crosslinking. Dynamic rheological analysis showed that the G' values of the composites, upon the addition of RBC-graphite, were changed to some extent. This demonstrates that the presence of a strongly developed network of fillers will ensure a reinforcing characteristic in a polymer matrix.