• Polymer(Korea)
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• v.37 no.5
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• pp.656-662
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• 2013

The flexible patterned cover film was made by a simple solution coating process using polymethyl methacrylate (PMMA) solution with glass beads. The effect of patterned cover film on the efficiency of solar cell has been investigated. It was found that the relative solar cell efficiency increased up to 3.4% with the incident light angle between $0-90^{\circ}$ by the sphere shape of glass bead coated on the film surface. This was understood that the loss of transmittance and scattering due to the light directional dependency on solar cell were minimized because the light entered glass beads normal to its surface regardless of incident light angle. The maximum relative solar cell efficiency was achieved when glass bead shape on the film is hemisphere and the relative efficiency increased with increasing the amount of glass bead on the film surface. However, too much glass beads on the film surface resulted in the lower relative solar cell efficiency due to the lowering of transmittance as well as the occurring of light interference.

• Polymer(Korea)
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• v.38 no.6
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• pp.801-808
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• 2014

Ion diffusion and chemical binding to acrylic polymer were investigated in a solid film. The composition of acrylic monomers containing amino group and carboxylic acid was adjusted for rapid ion migration in the film. p-Methylred (PMR) and phenolphthalein derivatives were optically sensitive to the concentration of proton and hydroxyl anion, respectively and verified the ion migration through the film layers. A rapid proton migration was observed in the film of a high amino content. On the other hand, $OH^-$ migration occurred rapidly in a high content of carboxylic acid group. The proton migration occurred through the internal layer as well as surface layer of a film and was reversible during 50 repetition examination. Copper(II) ion migration was examined with a Rhodamine-containing polymer film. The light absorption and emission spectra of a Rhodamine-Cu complex showed the key contribution of carboxylic acid group to the Cu(II) migration in a film.

• 발명특허
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• v.29 no.3 s.333
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• pp.55-58
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• 2004

• Polymer Science and Technology
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• v.3 no.3
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• pp.185-206
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• 1992

• Polymer Science and Technology
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• v.20 no.1
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• pp.16-29
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• 2009

• Composites Research
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• v.18 no.6
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• pp.26-33
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• 2005

The mechanical properties of composite materials may severely degrade in the presence of damage. Especially, the high-velocity impact such as bird strike, a hailstorm, and a small piece of tire or stone during high taxing, can cause considerable damage to the structures and sub-system in spite of a very small mass. However, it is not easy to detect the damage in composite plates using a single technique or any conventional methods. In this paper, the PVDF(polyvinylidene fluoride) film sensors were used for monitoring high-velocity impact damage initiation and propagation in composite laminates. The WT(wavelet transform) and STFT(short time Fourier transform) are used to decompose the sensor signals. A ultrasonic C-scan and a digital microscope are also used to examine the extent of the damage in each case. This research shows how various sensing techniques, PVDF sensor in particular, can be used to characterize high-velocity impact damage in advanced composite.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.445-450
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• 2011

We studied the adhesion characteristics of polymer films (PC, PET, EVA) treated by atmospheric pressure plasma. The process parameters were the frequency, gas flow, and treatment time; we studied the effects of these parameters on the adhesion characteristics of the polymer materials. We used de-ionized water and diiodomethane as the polar and nonpolar solvents, respectively, for measuring the contact angles, and subsequently calculated the surface free energy of each polymer film. The adhesion characteristics were studied by carrying out a $180^{\circ}$ peel-off test. The polymer films treated with plasma developed a hydrophilic surface, which led to increased surface free energy and improved adhesion properties. From the results for contact angle, surface free energy, and adhesion strength, we obtained the optimal plasma-treatment conditions.

• Polymer(Korea)
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• v.25 no.2
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• pp.293-301
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• 2001

Electrically conductive carbon fiber/high density polyethylene (CF/HDPE) composite films were fabricated by new method, so called electron-ion technology (EIT) and the effects of CF epoxy sizing on the volumetric resistivity. tensile strength and interphase properties of the films were investigated. While epoxy sizing increased conductivity of composite films resulting from enhanced tunneling effect it reduced interphase adhesion between CF and HDPE because polar epoxy sizing and nonpolar HDPE are incompatible. Consequently epoxy sized CF(CF(S)) caused significant reduction in the volumetric resisitivity and tensile strength of composite films when compared with unsized CF(CF(U)). Epoxy sizing reduced nucleating efficiency of CF(S), therefore CF(S)/HDPE composite films showed nonuniform transcrystalline layer when compared with CF(U)/HDPE composite films.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1064-1067
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• 2012

Recently, there is a growing interest in vegetable oils, cheap and abundant renewable natural resources. Vegetable oils can be used as raw materials for ecofriendly biodegradable polymer materials. In this study, poly(${\beta}$-amino esters) were synthesized by polymerization reaction of acrylated epoxidized soybean oil (AESO) and 2-aminoethanol. Various polymer films were prepared by changing the molar ratio of AESO to 2-aminoethanol. The formation of C-N bonds in poly(${\beta}$-amino ester) was confirmed using FT-IR. Gel contents higher than 98% confirmed the synthesis of crosslinked polymer networks. Tensile strengths and elongation at breaks of polymer films ranged from 0.3 to 1.3 MPa and 32 to 55%, respectively. Polymer films degraded 2 to 7% of the initial weight in 35 days in phosphate buffer solution (pH 7.2) containing lipase enzyme.

• Polymer(Korea)
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• v.31 no.4
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• pp.308-314
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• 2007

A composite film of polyurethane(PU)-graft-poly(acrylic acid) (PAAc)/polyaniline (PU-g-AAc/PANI) was successfully fabricated for the purpose of adding conductivity on the surface of a general purpose polymer and improving adhesive property between the general purpose polymer and conducting polymer layer. The results from ATR-FTIR and XPS analyses also supported the successful synthesis of the composite film by showing characteristic peaks for every step. A low surface resistivity of $2{\times}10^3\;ohm/sq$ proved the surface conductivity of synthesized PU-g-AAc/PANI film and the surface resistance decreased with increasing the amount of grafted AAc, which acted as a dopant for PANI film.