• Journal of the Korean Ceramic Society
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• v.40 no.7
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• pp.625-631
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• 2003

Recent work at USC has focused on strategies to enhance the toughness and overall mechanical performance of polymer foams for use in lightweight sandwich structures. Both mechanical and chemical approaches have been employed with reasonable success. Fiber reinforcement, though difficult from a processing perspective, can lead to substantial enhancements in toughness and strength, while reducing friability. Chemical modifications are also challenging from a processing perspective, but can produce similar enhancements in performance. Efforts to enhance performance of phenolic foam and PVC foam through fiber reinforcement and chemical modification are described, along with the resulting enhancements in performance.

• Textile Coloration and Finishing
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• v.20 no.4
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• pp.21-30
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• 2008

To understand the complex hydrogen bonding structure, several phenolic derivatives and benzoxazine model compounds are synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR). The estimation of molar extinction coefficients for various types of hydrogen bonding species is systematically carried out by the curve-resolving of FT-IR spectra. The distribution of hydrogen bonding species in benzoxazine model dimers is quantitatively analyzed. It is revealed that benzoxazine dimers and BA-a polybenzoxazine are mainly composed of intramolecular interaction rather than intermolecular interaction.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.756-761
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• 1999

• Journal of the Korean Ceramic Society
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• v.52 no.4
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• pp.284-289
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• 2015

This study examined carbon layer coating on silicon carbide (SiC) fibers by utilizing solid-state and wet chemistry routes to confer toughness to the fiber-reinforced ceramic matrix composites, as an alternative to the conventional pyrolytic carbon (PyC) interphase layer. Electrophoretic deposition (EPD) of carbon black nanoparticles using both AC and DC current sources, and the vacuum infiltration of phenolic resin followed by pyrolysis were tested. Because of the use of a liquid phase, the vacuum infiltration resulted in more uniform and denser carbon coating than the EPD routes with solid carbon black particles. Thereafter, vacuum infiltration with controlled variation in phenolic resin concentration, as well as the iterations of infiltration steps, was improvised to produce a homogeneous carbon coating having a thickness of several hundred nanometers on the SiC fiber. Conclusively, it was demonstrated that the carbon coating on the SiC fiber could be achieved using a simpler method than the conventional chemical vapor deposition technique.

• Carbon letters
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• v.16 no.1
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• pp.25-33
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• 2015

The prime objective of this research was to study the influence of hot-pressing pressure and matrix-to-reinforcement ratio on the densification of short-carbon-fiber-reinforced, randomly oriented carbon/carbon-composite. Secondary objectives included determination of the physical and mechanical properties of the resulting composite. The 'hybrid carbon-fiber-reinforced mesophase-pitch-derived carbon-matrix' composite was fabricated by hot pressing. During hot pressing, pressure was varied from 5 to 20 MPa, and reinforcement wt% from 30 to 70. Densification of all the compacts was carried at low impregnation pressure with phenolic resin. The effect of the impregnation cycles was determined using measurements of microstructure and density. The results showed that effective densification strongly depended on the hot-pressing pressure and reinforcement wt%. Furthermore, results showed that compacts processed at lower hot-pressing pressure, and at higher reinforcement wt%, gained density gradually during three densification cycles and showed the symptoms of further gains with additional densification cycles. In contrast, samples that were hot-pressed at moderate pressure and at moderate reinforcement wt%, achieved maximum density within three densification cycles. Furthermore, examination of microstructure revealed the formation of cracks in samples processed at lower pressure and with low reinforcement wt%.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.549-555
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• 2012

Silicon carbide(SiC) exhibits many unique properties, such as high strength, corrosion resistance, and high temperature stability. In this study, a SiC-fiber web was prepared from polycarbosilane(PCS) solution by employing the electrospinning process. Then, the SiC-fiber web was pyrolyzed at $1800^{\circ}C$ in argon atmosphere after it was subjected to a thermal curing. The SiC-fiber web (ground web)/phenolic resin (resol) composite was fabricated by hot pressing after mixing the SiC-fiber web and the phenolic resin. The SiC-fiber web composition was controlled by changing the fraction of filler (filler/binder = 9:1, 8:2, 7:3, 6:4, 5:5). Thermal conductivity measurement indicates that at the filler content of 60%, the thermal conductivity was highest, at 6.6 W/mK, due to the resulting structure formed by the filler and binder being closed-packed. Finally, the microstructure of the composites of SiC-fiber web/resin was investigated by FE-SEM, EDS, and XRD.

• Composites Research
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• v.25 no.3
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• pp.76-81
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• 2012

Atmospheric pressure plasma treatment on carbon nanotube (CNT) surfaces was performed to modify reinforcement effect and interfacial adhesion of carbon fiber reinforced CNT-phenolic composites. The surface changes occurring on CNT treated with plasma were analyzed by using Fourier transform infrared spectroscope (FT-IR). The significant improvement of wettability on CNT was confirmed by static contact angle test after plasma treatment. Such plasma treatment resulted in a decrease in the advancing contact angle from $118^{\circ}$ to $60^{\circ}$. The interfacial adhesion between carbon fiber and CNT-phenolic composites increased by plasma treatment based on apparent modulus test results during quasi-static tensile strength. Furthermore, the proposed database offers valuable knowledge for evaluating interfacial shear strength (IFSS).

• Composites Research
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• v.33 no.6
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• pp.329-335
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• 2020

In this study, the thermo-rheological behaivors of petroleum pitches with different softening points were studied, and a B-stage phenolic resins/petroleum pitches blends were prepared by adding petroleum pitches to the phenolic resins. As a result, the petroleum pitch with different softening points decreased the fluidity of the petroleum pitch as the Quinoline insoluble (QI) content increased and showed the viscous properties of the solid. In addition, the effect of adding petroleum pitches having different softening points on the thermo-rheological properties of phenolic resins was investigated. When petroleum pitch with a high softening point was added, the fluidity of the phenolic resin was reduced, and the hardening behavior was fast. It was possible to control the curing rate and curing behavior of the phenolic resin by adding petroleum pitches of different softening points. Among them, the phenolic resin mixture to which P-Pitch 2 was added has a higher fluidity than other blends under the same curing temperature condition.

• Food Science and Preservation
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• v.18 no.1
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• pp.13-17
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• 2011

The proximate composition, and the levels of total phenols, phenolic acids, and DPPH radical scavenging activity in Cheongdobansi persimmon fruits assayed during development (from July to October), were investigated. All of moisture, crude protein and crude fiber contents decreased as picking time was delayed, however, crude fat content rose. Crude fiber content increased after September. Total phenol content tended to fall during development. The principal phenolic acids were chlorogenic acid, caffeic acid, p-coumaric acid and salicylic acid; the level of each phenolic acid tended to decrease during development. DPPH radical scavenging activity fell as picking time was delayed. Thus, harvest time influenced the levels of chemical components and the antioxidative properties of persimmon fruit. It follows that unripe fruit may be utilized as a raw material yielding many useful products.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.130-133
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• 2005

An experimental and theoretical study was carried out to estimate the foaming characteristics in the pultrusion process of phenolic foam composite. For the experimental study, a lab-scale pultrusion apparatus was constructed. Methylene chloride(CH2Cl2) was used as a physical blowing agent, glass fiber roving was used as reinforcement and the polymer used was a resol type phenolic resin. Pultruded products were observed to count bubble size by a SEM(Scanning Electron Microscopy). For the theoretical study, a model for bubble growth in a gradually hardening resin was considered and solved for a few foaming conditions.