• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1703-1711
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• 2000

Microstructural morphology of molded composites of thermotropic liquid crystalline polymer(LCP) and polyamide 6 (PA6) has been studied as a function of epoxy fraction. Injection-moulding of a thin composite plaque at a temperature below the melting point of the LCP fibrils by suing the extruded LCP/PA6 pellets produced multi-layered structures: 1) the surface skin layer with thickness of 65-120 ym exhibiting a transverse orientation, 2) the sub-skin layer with an orientation perpendicular to the surface skin, i.e. in the flow direction, 3) the core layer with arc-curved flow patterns. Similar microstructural orientations were observed in the respective layers for the composite plaques with different fractions of epoxy.

• The Korean Journal of Rheology
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• v.3 no.1
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• pp.68-75
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• 1991

상업적으로 많이 이용되는 폴리에틸렌테레프탈레이트(PET)에 액정중합체(LCP)인 열방성 폴리에스터를 첨가하여 유변학적 특성을 조사하고 전단속도와 혼합비에 따른 LCP domain의 형태 변화를 고찰하였다. 모체고분자 내 구형과 타원형을 이루는 LCP domain들 은 신장력에 의해 피브릴 구조의 변형되고 이 피브릴은 흐름방향으로 배향되어 용융체에 윤 활제와 같은 역할을 함으로써 용융점도의 감소를 보이는데 특히 높은 전단속도 영역에서 LCP가 30wt%까지 첨가될수록 큰 폭으로 감소하였다. 주사식 현미경(SEM)의 관찰로부터 LCP domain의 피브릴구조를 확인할 수 있었고 또한 LCP domain의 형태 변화가 용융점도 가 감소에 직접 관계됨을 확인할 수 있었다.

• The Korean Journal of Rheology
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• v.10 no.1
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• pp.50-56
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• 1998

폴리아릴레이트(PAr)와 열방성 액정고분자(LCP)블렌드의 상용성과 두 고분자 사이 의 에스터 교환반응을 시차 주사 열분석기 (DSC)와 Fourier transform 적외선 분광분석기 (FT-IR spectroscopy)로 연구하였다. DSC를 이용하여 PAr-LCP 블렌드의 유리전이온도 (Tg)를 관찰한 결과, 두 개의 Tg가 관찰되었다. 측정된 Tg 결과로부터 블렌드 각 상에 녹아 있는 두성분의 상거동을 조사했으며 그결과 LCP가 PAR-rich 상에 녹아 들어간 양이 PAr 이 LCP-rich 상에 녹아 들어간 양보다 더 많음을 알수 있었다. 이러한 결과는 두 고분자 사 이에 부분적으로 상용성이 있음을 의미한다. 액정고분자의 이방성을 고려하여 PAr-LCP 블 렌드의 고분자-고분자 상호작용계수($\chi$12)는 0.069~0.076의 값으로 계산되었다. 두 고분자사 이의 에스터 교환반응를 조사하기 위하여 DSC내에서 열처리한 결과, 열처리 후에 PAr과 LCp의 Tg는 열처리하기 전에 비해 더 큰폭으로 두 Tg의중간값으로 이동하였다. 열처리한 PAr-LCP 블렌드를 FT-IR spectroscopy로 분석한 결과, 순수한 PAr과 LCP에 없는 새로운 에스터기의 특성피이크가 발견되었다. 이와 같은 열분석과 FT-IR spectroscopy 연구 결과 로부터 주어진 열처리 조건에서 PAr과 LCP 사이에 에스터 교환반응이 일어났음을 확인할 수 있었다.

• The Korean Journal of Rheology
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• v.2 no.2
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• pp.56-65
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• 1990

열방성 액정고분자와 폴리카보네이트를 대상 수지로 하여 용융혼합기로 액정고분자 의 함량, 혼합속도 및 온도등의 변환에 따른 훈련 특성을 측정하고 고분자 혼합물의 혼련조 건과 유변학적 특성 모폴로지 사이의 관계를 조사하였다. 혼련 토크는 100rpm의 혼합속도 에서 극소값을 보이며 혼합기 내의 전단속도가 낮기 때문에 혼력에의해서는 LCP가 섬유상 으로 형성되지 못하고 구형의 입자로 존재함을 알수 있었다. 혼합물의 점도는 시험된 전단 속도 영역에서 순수한 고분자보다 현저히 낮으며 5wt%의 소량 첨가로도 5배의 점도 감소 효과를 보이고 LCP함량이 약 30wt%일 경우 점도 및 혼합에너지가 최소로 되었다. Capillary 레오미터의 실험결과 LCP/PC의 점도비가 1보다 작거나 같튼 전단장하에서 LCP 는 섬유상을 형성하였으며 높은 점도비의 경우 LCP의 변형이 어려워 구형의 입자로 존재하 였다. 또한 혼합물의 PC Tg 이동은 에스터르 교환 반응에 의한 부분적인 혼화성의 증가에 기인함을 알수 있었다.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.132-132
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• 2006

Filler loading (fiber or particulate) usually increases the melt viscosity of polymers. In contrast, the addition of these fillers and fibrillation of thermotropic liquid crystalline polymer (LCP) jointly decreased the viscosity of polymer melts to lower than those of pure component polymers, filler-loaded or LCP-blended ones; and even decreased the viscosity with increasing filler loading. Termed as rheological hybrid effect, this phenomenon correlated well with the LCP fibrillation in these ternary systems. Research taking fillers of various shapes and sizes showed that the filler addition promoted the LCP fibrillation, depending upon thermodynamic and dynamic factors involved.

• Macromolecular Research
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• v.11 no.4
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• pp.224-230
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• 2003

The blends of polypropylene (PP) with glass filled thermotropic liquid crystalline polymer (LCP-g) have been prepared by melt mixing techniques at different blend ratios. The thermal, dynamic mechanical, crystalline and morphological characteristics of these blends were investigated. Higher percent crystallinity was observed for 10% level of LCP-g in the blend in comparison to that of other blend ratios. The thermal stability increased with LCP-g concentration in the blend with PP. The variation of storage modulus, stiffness and loss modulus as a function of blend ratios suggested the phase inversion at the 50% level of LCP-g in the blend. The scanning electron microscopy (SEM) photographs showed the creation of voids and destruction of the fiber structures during the dynamic mechanical measurements. Processing behavior of the blends depended on the fiber forming characteristics of LCP-g, which again varied with the molding temperatures.

• Composites Research
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• v.12 no.6
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• pp.53-64
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• 1999

Microstructural morphology and bending strengths of moulded composites of thermotropic liquid crystalline polymer(LCP) and polyamide 6 (PA6) have been studied as a function of epoxy fraction. Injection-moulding of a composite plaque at a temperature below the melting point of the LCP fibrils generated a multi-layered structure: the surface skin layer with thickness of $65\;-\;120{\mu\textrm{m}}$ exhibiting a transverse orientation; the sub-skin layer with an orientation in the flow direction; the core layer with arc-curved flow patterns. The plaques containing epoxy 4.8vol% exhibited superior bending strength and large fracture strain. With an increase of epoxy fraction equal to and beyond 4.8vol%, geometry of LCP domains was changed from fibrillar shape to lamella-like one, which caused a shear-mode fracture. An analysis of the bending strength of the composite plaques by using a symmetric layered model beam suggested that addition of epoxy component altered not only the microstructural geometry but also the elastic moduli and strengths of the respective layers.

• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.49-58
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• 1997

LCP/PA alloy was prepared by blending poly(${\varepsilon}-caprolactam$) (PA) with liquid crystal polyester, Vectra (LCP) having high elasticity and strength. The alloy prepared amorphous PA with more than 10 parts of thermotropic LCP had poor compatibility. To increase the compatibility of the alloy, compatibilizing agent, poly(glycinylmaleimide-co-methylmetacrylate)[poly(GMI-co-MMA)] copolymer was prepared by copolymerizing N-glycinylmaleimide(GMI) with methylmetacrylate(MMA). And then, it was blended with LCP and PA to produce LCP/PA alloy having an excellent compatibility. The compatibility characteristics of the alloy prepared from LCP and PA using the poly(GMI-co-MMA) was determined by measuring the thermal characteristics of glass transition temperature of nematic LCP, and rheological properties, and also high rate impact and flexual characteristics of the alloy were determined.

• Korean Journal of Materials Research
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• v.10 no.5
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• pp.350-353
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• 2000

Thermotropic liquid crystalline polymer(LCP) has been used for the alignment of ferroelectric liquid crystal (FLC) molecules and the surface morphology of the resulting polymeric thin film has been observed by atomic forced microscope. The uniform alignment of FLC molecules on the surface of thermotropic LCP thin film was obtained even though microgroove structures were not formed. The contrast ratio of sample cell was about 23:1 including two polarizers and a good memory capability due to the bistability of FLC was obtained. After AC field stabilization at 20V, the typical stripe-shaped patterns appeared.

• Proceedings of the Korean Fiber Society Conference
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• 1998.10a
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• pp.236-239
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• 1998

The in situ composites based on poly(ethylene 2,6-naphthalate) and thermotropic liquid crystalline polymer (LCP) have been an area of increasing interest and study, since LCP exhibits high chemical stabilities and excellent thermo mechanical properties such as high strength and modulus. In a binary, however, poor compatibility and interfacial adhesions between two phases frequently results in deteriorated mechanical properties. (omitted)