• Polymer(Korea)
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• v.36 no.4
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• pp.407-412
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• 2012

The characteristics of nylon6/ionomer semi interpenetrating networks (IPN) as a molded-in-color (MIC) compound had been studied, and comparison was made with nylon6/ionomer blends. Nylon6/ionomer semi IPN shows better homogeneity in phase morphology than nylon6/ionomer blend, and it caused better anti-scratching performance than the blend. This semi IPN structure resulted in lowered crystallization rate, increased melt viscosity and less temperature dependency of viscosity. As a result, we may expect the enhancement of melt processing characteristics in an injection molding process using nylon6/ionomer semi IPN as a MIC compound.

• Elastomers and Composites
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• v.49 no.3
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• pp.199-203
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• 2014

Terpolymer syrups were photopolymerized from 2-ethylhexyl acrylate, 2-hydroxylethyl acrylate and isobornyl acrylate to prepare acrylic pressure sensitive adhesives (PSAs). After polymerization, various crosslinkers as 1,6-hexanediol diacrylate (HDDA), poly (ethylene glycol) diacrylate (PEGDA, Mn = 250, 575, and 700) were added and then UV-irradiated to prepare the semi-IPN type PSAs. Their adhesion performance and storage modulus (G') were strongly dependent on their chemical structure and molecular weight of the crosslinkers. Optical properties such as transmittance (> 92.5 %), haze (< 1.0 %) and color-difference (< 0.3) of PSAs samples were not affected by crosslinker types used in this study.

• Polymer(Korea)
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• v.34 no.3
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• pp.220-225
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• 2010

The optical properties and dimensional stability of polyethersulfone(PES) retardation film have been studied as function of chain orientation and the temperature applied to PES retardation film. It was confirmed that the appropriate retardation values of $R_e$ and $R_{th}$ for the retardation film application were able to obtain by the chain orientation and these values could be controlled by the chain relaxation through the thermal annealing process. It was found that unstable $R_e$ and $R_{th}$ values were shown by the repeated cooling and heating applied to the retardation films but this could be stabilized by means of the annealing process after stretching of PES film. The dimensional shrinkage due to the chain orientation was found as temperature increase and the intrinsic thermal expansion of PES appeared after shrinking. The shrinkage of PES films affected by the chain orientation and thermal annealing dramatically but the effect on the coefficient of thermal expansion was found to be negligible.

• Polymer(Korea)
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• v.36 no.3
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• pp.393-400
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• 2012

The characteristics of indium tin oxide (ITO) thin film deposited on polyethersulfone (PES) film by low temperature E beam has been studied for the flexible photovoltaic devices. It was found that the substrate temperature in the deposition process affected the crystallization behavior of ITO during the post low temperature annealing process. Higher substrate temperature resulted in the increase of crystallinity of annealed ITO. Consequently, the lowering of sheet resistivity and better transmittance were obtained. Crystallization of ITO during the annealing process was facilitated by using oxygen gas in the deposition process and resulted in the enhancement on sheet resistivity and transmittance of ITO. The surface roughness of PES film prohibited the crystallization of ITO during the annealing process and it caused the increase of sheet resistivity and the decrease of transmittance of ITO.

• Polymer(Korea)
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• v.35 no.2
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• pp.183-188
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• 2011

Pentaerytritol triacrylate (PETA) was synthesized by a condensation reaction between pentaerytritol and acrylic acid. The highest yield of PETA was obtained when heptane was used as a solvent under the 1:4 mole ratio of pentaerytritol and acrylic acid. The 6-functional urethane acrylates(UA) were also synthesized by a condensation reaction between PETA and diisocyanate. Cured films were prepared from the mixtures of UA oligomer, reactive diluents and UV initiator to investigate their physical properties. The thermal stability of the aliphatic urethane acrylate was better than that of the aromatic urethane acrylate. The UA-2 showed good hardness and scratch resistance properties while the UA-l with a high degree of curing density exhibited a better chemical resistance. All the UA oligomers showed fairly good adhesion strengths but the other physical properties of UA-3 were poor due to its low curing density.

• Polymer(Korea)
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• v.35 no.2
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• pp.146-151
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• 2011

The physical properties of poly (ethylene 2,6-naphthalate) (PEN) copolymers were studied. PEN copolymers were synthesized successfully from the mixtures of ethylene glycol(EG), 1,3-propanediol (PD) and l,4-butanediol (BD) with 2,6-dimethyl naphthalene dicarboxylate. The results indicated that PEN copolymers showed an amorphous state when the content of BD(PD) in applied EG/BD(EG/PD) mixtures was less than 40% during the polycondensation. As a result, the lowering of thermal properties, orientation, and mechanical properties was found, however, the dimensional stability was improved. This is a promising result to apply the synthesized PEN copolymers as flexibles substrates.

• Polymer(Korea)
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• v.38 no.5
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• pp.650-655
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• 2014

The degradation characteristics of perfluoropolyether (PFPE) derivatives currently being used as computer hard disk lubricants have been investigated. Especially, we considered the effects of end group on degradation behavior of PFPE derivatives. It was found that the degradation of PFPE derivatives in the presence of $Al_2O_3$ involves two degradation mechanisms such as thermal degradation and Lewis acid disproportionation by $AlF_3$ which was mainly formed by oxide-to-halide reaction between $Al_2O_3$ and the degraded PFPE. The end groups were strongly related to Lewis acid disproportionation of PFPE derivatives, and it is due to the difference of electron donating ability in the each end groups. Even if PFPE derivatives have same repeating unit in the main chain, Lewis acid disproportionation was prohibited by higher electron donating ability by the end group which caused the high electron density at the acetal group in the repeating unit.

• 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.33 no.4
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• pp.371-376
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• 2009

The 1,3-propane diol has been introduced as a co-monomer with ethylene glycol to polymerize the poly(ethylene/propylene naphthalate) in order to improve the dimensional stability of poly(ethylene naphthalate) for a possible flexible substrate material. Based on $^1H$-NMR results, it was found that poly (ethylene/propylene naphthalate) has been synthesised successfully. Introducing 1,3-propane diol resulted in the amorphous state in polyester as well as lowering of glass transition and thermal degradation temperature. Coexisting relatively longer propylene segment compared with ethylene in synthesized polyester caused less orientation behavior and reducing thermal expansion coefficient. This is a promising result for poly (ethylene/propylene naphthalate) to apply a flexible substrate.

• 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.