• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.466-469
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• 2002

Polyurethane(PU)은 segmented 블록공중합체로써 상온보다 높은 유리전이온도(glass transition temperature, Tg)를 갖는 hard segment(H.S)와 상온보다 낮은 Tg를 갖는 soft segment (S.S)로 구성되어 있다. 이들 두 segment간의 열역학적 불친화성으로 인해 미세 상분리 구조를 갖는다$^1$. 그 결과 hard segment-rich hard domain과 soft segment-rich soft matrix의 구조를 이룬다. 이중 hard domain(HD)은 상온에서 glassy한 성격을 띄므로 물리적 가교점과 충진제의 역할을 하며 soft domain(SD)은 rubbery한 성질을 가지므로 polurethane에 탄성을 부여하는 역할을 한다. (중략)

• Proceedings of the Korean Fiber Society Conference
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• 2003.10b
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• pp.195-196
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• 2003

Polyurethane(PU)은 물리적 화학적 성질이 매우 다른 두 segment(hard/soft)로 이루어진 block copolymer로서 상온에서 미세상분리된 구조를 가진다. 이런 미세 상분리 구조는 PU의 물리적 성질을 결정하는 가장 중요한 요소이며, hard segment(H/S)의 화학적 구조에 따른 PU사슬의 강직성은 H/S의 packing및 상분리도에 큰 영향을 미친다. 본 연구에서는 H/S의 화학적 구조를 변화시켜 사슬의 강직성이 서로 다른 다양한 PU을 합성하였으며 Synchrotron SAXS와 FTIR-dichioism을 이용하여 PU 사슬의 강직성에 따른 거시적인 domain의 변형거동과 미시적인 사슬의 변형거동을 관찰 하였다. (중략)

• Proceedings of the Korean Fiber Society Conference
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• 1998.04a
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• pp.5-8
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• 1998

Polyurethane elastomers are segmented cocoplymer with an [HS]n-type structure. Typically, these materials are two-phase systems, prepared from relatively polar and stiff component called the hard segment(H) and relatively flexible component known as the soft segment(S). Diisocyanate and chain extender together form the hard segment, which is dispersed within a matrix of the soft segment, composed of the macrodiolos.(omitted)

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.1
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• pp.119-124
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• 2001

Dimethyl terephthalate (DMT). 1.4-butanediol (1.4-BD) and poly (tetramethylene ether) glycol (PTMG) in the molecular weight of 2000 (g/mol) were used to synthesize poly(ether-b-ester) thermoplastic elastomers (TPEEs). The final copolymers were annealed to improve thermal stability at elevated temperatures and mechanical properties. This study showed that as the proportion of soft segment increases melting temperature and degree of crystallinity of TPEEs decrease constantly. In case of mechanical properties like flexural strength and flexural elastic modulus. $35-PTMG^{2000}$ indicates the highest values due to more efficient physical interlock.

• Polymer(Korea)
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• v.24 no.2
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• pp.149-158
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• 2000

Oil-absorptive expanded polyurethane (EPU) was prepared with a lypophilic polyol, polypropyleneglycol (PPG) as the soft segment, and toluenediisocyanate (TDI) and $H_2O$ as the hard segment. PPGs haying various average molecular weights ((equation omitted) : 1000, 2000, 3000) were employed to investigate that the soft segment content was consequent on the oil-absorptivity and the mechanical properties of the EPUs. As (equation omitted) of PPG was decreased from 3000 to 1000, the oil-absorptivity and the tensile strength of the EPUs increased from 1460 to 3010% and from 0.26 to 0.55 $kg_{f}$ /$cm^2$ respectively. As the hard segment content ratio, ${\gamma}$ ([NCO]/[OH]) was increased from 1.0 to 1.2, the tensile strength of the EPUs increased from 0.56 to 0.95 $kg_{f}$ /$cm^2$, due to the formation of allophanate and/or biuret bondings. However, as the surfactant (S-A) content was increased from 1.0 to 2.5 pbw, the oil-absorptivity was decreased from 3634 to 3312%, due to the formation of closed cell structures.

• 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.

• 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.

• 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.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.237-242
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• 2020

This paper deals with relative position estimation using a Kalman filter (KF) based on inertial sensors that have been widely used in various biomechanics-related outdoor applications. In previous studies, the relative position is determined using relative orientation and predetermined segment-to-joint (S2J) vectors, which are assumed to be constant. However, because body segments are influenced by soft tissue artifacts (STAs), including the deformation and sliding of the skin over the underlying bone structures, they are not constant, resulting in significant errors during relative position estimation. In this study, relative position estimation was performed using a KF, where the S2J vectors were adopted as time-varying states. The joint constraint and the variations of the S2J vectors were used to develop a measurement model of the proposed KF. Accordingly, the covariance matrix corresponding to the variations of the S2J vectors continuously changed within the ranges of the STA-causing flexion angles. The experimental results of the knee flexion tests showed that the proposed KF decreased the estimation errors in the longitudinal and lateral directions by 8.86 and 17.89 mm, respectively, compared with a conventional approach based on the application of constant S2J vectors.

• Fibers and Polymers
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• v.4 no.3
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• pp.114-118
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• 2003

The prepolymer and the final polyurethane (PU) block copolymer were synthesized by reacting 4,4-methylene bis(phenylisocyanate) with poly(tetramethylene glycol) and the prepolymer with 1,4-butanediol as a chain extender, respectively, to investigate the relation between phase separation and it's resulting properties. According to FT-IR data, the phase separation of hard and soft segments in the prepolymer and the PU block copolymer grew bigger by increasing the hard segment content, and the PU showed more dominant phase separation than the prepolymer. The heat of fusion due to soft segments decreased in both the prepolymer and the PU by increasing the hard segment content, whereas the heat of fusion due to hard segments increased in the PU did not appear in the prepolymers. The breaking stress and modulus of the prepolymer increased by increasing the hard segment content, and the elongation at break decreased gradually, and the PU showed the highest breaking stress and modulus at 58% hard segment content. However, the best shape recovery of the PU was obtained at 47% hard segment content due to the existence of proper interaction among the hard segments for shape memory effect. Consequently, the mechanical properties and shape memory effect of the PU were influenced by the degree of phase separation, depending on the incorporation of chain extender as well as the hard segment content.