• Proceedings of the Korean Fiber Society Conference
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• 1998.10a
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• pp.203-206
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• 1998

열가소성 탄성체(Thermoplastic elastomers)의 일종인 polyurethane은 상온보다 높은 유리전이온도(T$_{g}$)를 갖는 hard segment(HS)와 낮은 T$_{g}$를 갖는 soft segment(SS)간의 열역학적 불친화성으로 인해 미세 상분리 구조를 갖는다. SS는 낮은 T$_{g}$로 인해 상온에서 rubbery한 성격을 나타내며 HS는 높은 T$_{g}$로 인해 물리적 가교 역할과 충진제 역할을 한다. Polyurethane은 중합당시의 조성이나 중합방법에 따라 다양한 내부구조를 갖으며 이런 내부구조의 변화에 따른 물리적 성질의 변화 역시 다양하다. (중략)

• Polymer(Korea)
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• v.25 no.1
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• pp.33-40
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• 2001

Fluorinated polyurethane elastomers were synthesized by two step polyaddition of a perfluorinated polyether diol(trade name of Fomblin $ZDOL^{\circledR}$) and diisocyanates such as 4,4'-diphenyl methane diisocyanate(MDI) and toluene 2,4-diisocyanate(TDI). In order to control the Fomblin moiety of the soft segment in the synthesized elastomers to 10~50%, polyether type polyols such as polypropylene glycol(PPG) and polytetramethylene glycol(PTMG) were mixed during the polymerization reaction. Ethylene diamine or 1,4-butane diol was used as chain extenders. The structure and average molecular weight of the produced polyurethanes were confirmed by using FT-IR, $^1H-NMR$, DSC, and GPC. The surface properties were analyzed by using X-ray photoelectron spectroscopy(XPS) and contact angle meter. From the results of the surface analysis it was concluded that the fluorine groups were localized on the surface rather than the inside of the polyurethane films.

• Proceedings of the Korean Fiber Society Conference
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• 1996.10a
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• pp.465-467
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• 1996

A series of thermoplastic polyurethane copolymers were prepared from polypropyleneglycol(PPG, MW 3000), 1,4-butanediol, Isophorone diisocyanate(IPDI) and dibutyltin dilaurate(BBT) as catalyst. Studies have been made on the effects of molar ratio of isocyanate /polyol/chain extender on the properties such as tensile and thermal properties. By varying the ration of hard to soft segments, TPU ranging from soft elastomeric polymer to relatively hard elastoplastics and be obtained. The storage modulus and glass transition temperature of TPU increased with increasing the hard segment content.

• Elastomers and Composites
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• v.54 no.4
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• pp.271-278
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• 2019

Polyurethane elastomers (PUEs) were synthesized using trans-1,4-bis(isocyanatomethyl) cyclohexane (1,4-H₆XDI), poly(oxytetramethylene) glycol, 1,4-butanediol (BD), and 1,1,1-trimethylol propane (TMP). To control the molecular aggregation state and mechanical properties of these PUEs, hard segment contents of 20 and 30 wt% and BD/TMP ratios of 10/0 and 8/2 were chosen. Differential scanning calorimetry and small-angle X-ray scattering measurements revealed that the degree of microphase separation increased with an increase in both hard segment content and BD ratio. The Young's modulus and strain at break of the 1,4-H₆XDI-based PUE were 6-20 MPa and 5-15, respectively. Incorporation of 20% TMP as a cross-linking agent into BD increased the melting temperature of the hard segment chains, that is, heat resistance, and decreased the Young's modulus. This could be due to the low density of the physical cross-linking network and the dispersion of hard segment chains in the soft segment matrix in the PUE in the presence of 20% TMP.

• Proceedings of the Korean Fiber Society Conference
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• 1995.10a
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• pp.80-81
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• 1995

• Elastomers and Composites
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• v.27 no.3
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• pp.161-173
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• 1992

A series of polyurethane block copolymers based on hydroxyterminated poly(dimethyl siloxane), poly(propylene glycol) and poly(tetramethylene glycol) soft segments of molecular weights 1,809, 2,000 and 2,000, respectively, were synthesized. The hard segments consisted of 4,4'-diphenylmethane diisocyanate and 1,4-butanediol as the chain extender. Samples with different molar ratios were prepared. We tried to synthesize poly(dimethyl siloxane)-based polyurethane(PDMS-PU) containing a hard block as major fraction and a soft block as minor fraction for preparing toughened rigid systems. After a study of the pure PDMS-PU, poly(propylene glycol)-based polyurethane(PPG-PU) and poly(tetramethylene glycol)-based polyurethane(PTMG-PU), (mixed polyol)-based block copolymers and blends between PDMS-PU, PPG-PU and PTMG-PU were prepared, and characterized by means of differential scanning calorimetry, tensile testing and scanning electron microscopy. In (mixed polyol)-based PU and in lower hard segment content blends, macro-phase separation was shown, but blends with higher hard segment contents showed significant reduction in amounts of phase separation.

• The korean journal of orthodontics
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• v.28 no.6 s.71
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• pp.975-979
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• 1998

Our Goal of modified segmental osteotomy on maxilla accompanied by mandibular anterior subapical osteotomy was to get the best results from patients of bi-alveolar or bi-maxillary protrusion. In this study, cephalometric and photo (en face, profile) analysis have been compared to define the soft tissue change after surgery. Lip protrusion was efficiently reduced and nasolabial angle was much obtused. Although nose was a little widened, it was quite acceptable. Blood circulation on osteotomized segment was well maintained. This relatively simple methods could be successfully applied to many patients.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.23-26
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• 1999

Urethane block copolymers, containing soft segments such as polydimethylsiloxane (PDMS), polytertramethylene glycol(PTMG) and PEO-PPO-PEO (Poloxamer) block copolymer, were synthesized and examined for th vapor- phase separation of toluene from nitrogen stream by using vapor permeation equipment. Generally permeabilities of PTMG and PDMS based urethane membranes were higher than those of Poloxamer based urethane membranes. Organic vapor permeability in the PDMS and PTMG soft segment urethane membranes were greater than those measured in the Poloxamer films, due to more polymer swelling. The membranes performed best with toluene, with toluene/dry N2 seletivities ranging from 120~200 and permeablilities as high as 23$\times$10-9 mol/m2sPa for saturated toluene feeds at 23$^{\circ}C$.

• Polymer(Korea)
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• v.36 no.4
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• pp.513-518
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• 2012

Polyamide 12 (PA12) oligomers (oPA1) were prepared by dispersion polymerization of ${\omega}$-amino carboxylic acid and dibasic acid in a dispersion medium, thermally stable hydrocarbon liquid paraffin, YK-D130 (a step polymerization). The molecular weight and various properties of other oligomeric PAs (oPA2) obtained by bulk polymerization without the medium were compared with those of oPA1s. The oPA1s showed lighter white color and narrower molecular weight distribution than oPA2s at the same molecular weight. Moreover elastomeric poly(ether-block-amide) (PEBA)s were synthesized with oPA1 and oPA2 as hard segments and poly(tetramethylene glycol) (PTMG) as a soft segment. The molecular weight distribution, and mechanical property of the PEBA originated from the both oligomeric PAs were characterized.

• Journal of Korean Neurosurgical Society
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• v.60 no.1
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• pp.30-39
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• 2017

Objective : To compare the clinical outcomes and biomechanical effects of total disc replacement (TDR) and posterior cervical foraminotomy (PCF) and to propose relative inclusion criteria. Methods : Thirty-five patients who underwent surgery between 2006 and 2008 were included. All patients had single-level disease and only radiculopathy. The overall sagittal balance and angle and height of a functional segmental unit (FSU; upper and lower vertebral body of the operative lesion) were assessed by preoperative and follow-up radiographs. C2-7 range of motion (ROM), FSU, and the adjacent segment were also checked. Results : The clinical outcome of TDR (group A) was tended to be superior to that of PCF (group B) without statistical significance. In the group A, preoperative and postoperative upper adjacent segment level motion values were $8.6{\pm}2.3$ and $8.4{\pm}2.0$, and lower level motion values were $8.4{\pm}2.2$ and $8.3{\pm}1.9$. Preoperative and postoperative FSU heights were $37.0{\pm}2.1$ and $37.1{\pm}1.8$. In the group B, upper level adjacent segment motion values were $8.1{\pm}2.6$ and $8.2{\pm}2.8$, and lower level motion values were $6.5{\pm}3.3$ and $6.3{\pm}3.1$. FSU heights were $37.1{\pm}2.0$ and $36.2{\pm}1.8$. The postoperative FSU motion and height changes were significant (p<0.05). The patient's satisfaction rates for surgery were 88.2% in group A and 88.8% in group B. Conclusion : TDR and PCF have favorable outcomes in patients with unilateral soft disc herniation. However, patients have different biomechanical backgrounds, so the patient's biomechanical characteristics and economic status should be understood and treated using the optimal procedure.