• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.06a
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• pp.105-116
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• 1999

• Journal of the Korean Magnetics Society
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• v.6 no.5
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• pp.310-316
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• 1996

In this study magnetic properties of anisotropic ferrite bonded magnets produced by extrusion molding with a variety of magnetic field, extrusion mold temperature and extrusion rate were investigated. X-ray diffraction study showed the alignment of magnetic powder was decreased by molten flow in extrusion mold. When the temperature of extrusion mold was $20^{\circ}C$, the degree of alignment as much as 82% could be achieved under the applied magnetic field of 4 kOe. The bonded magnets having the remanence of 2.2 kG was able to fabricated by extrusion molding when the packing density of Sr-ferrite powder was 50 vol%.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.06a
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• pp.5-15
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• 1997

It is the objective of this study that by conducting the serni-solid extrusion using A12024, the effect of various process variables on the quality of extruded product and extrusion force is understood. The results of experiment are compared with those of finite element simulation in order to verify the effectiveness of the developed FE-simulation code. In order to simulate densification in the deformation of serni-solid material, the semi-solid material is assumed to be composed of solid region as porous skeleton following compressible visco-plastic model and liquid region following Darcy's equation for the liquid flow saturated in the interstitial space. Then the flow and deformation of the semi-solid alloy are analyzed by coupling the deformation of the porous skeleton and the flow of the eutectic liquid. It is assumed that initial solid fraction is homogeneous. Yield and plastic potential function presented by Kuhn and constitutive model developed by Gunasekera are used for solid skeleton.

• Journal of Ocean Engineering and Technology
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• v.11 no.2
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• pp.18-27
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• 1997

Al 6061 alloy reinforced with 10 vol.% ${\delta}-Al_2O_3$ short fiber was fabricated by Rheo-compocasting and squwwze cating. Extrusion processings were performed at temperatures from 40$0^{\circ}C$ to 55$0^{\circ}C$ with various extrusion ratio for curved shape dies. In proportion to the increase of extrusion ratios and temperatures, ultimate tensile strength for extruded materials improved. SEM observation of fractured surfsce was capcble oof accounting for fracture mechanism and bounding state of fiber and matrix.

• The Korean Journal of Rheology
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• v.5 no.1
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• pp.23-33
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• 1993

저밀도폴리에틸렌과 나일론6의 블렌드가 용융압출기의 사용에 의해 제조되었다. 제 조된 비상용 블랜드의 유변학적, 형태학적 분석을 통하여 이들사이의 상관관계를 조사하였 다. 전단속도, 계면장력, 용융점도, 분산상의 농도들에 대한 분산상의 크기의 의존성을 평가 하였다. 한편 신장유동에 의한 모폴로지 변화를 조사하기 위하여 기제조된 블렌드를 사용하 여 용융방사를 하였다. 이러한 방식실험으로부터 본연구에 사용된 저밀도 폴리에틸렌과 나 일론6는 분산상과 연속상의 신장점도의 상대적 크기에 무관하게 피브릴화가 되어 방사 연신 비의 증가에 의해 매우 가는 분산된 피브릴을 얻을수 있었다.

• The Korean Journal of Rheology
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• v.1 no.1
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• pp.63-70
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• 1989

고밀도 폴리에틸렌과 폴리프로필렌을 용융혼합하여 블렌드를 만들었다. 압출물의 morphology 와 유변학적 성질을 측정하고 그 용융하고 섬유의 X-선 회절, 인장 성질, 복굴 절률등과 관련하여 고찰하였다. 파단면의 SEM 사진으로부터 폴리에티렌 성분비가 25%, 50% 에서는 폴리프로필렌이, 75%에서는 폴리에틸렌이 연속상을 이루며 분산상은 고르게 분포함을 알았다 점도와 용융탄성은 모두 폴리에틸렌이 폴리프로필렌보다 크며 블렌드에서 는 그중간에 위치 하였다. 폴리에틸렌의 함량의 증가에 따라 압풀물의 제 1법선 응력차는 증가하였고따라서 방사 섬유의 복굴절률도 증가하였으며 초기 탄성률도 증가하는 경향을 보 였으나 결정 배향도는 조성 의존성을 갖지 않는다. 두 고분자의 비상용성으로 인해 강도는 짓선성에서 벗어나는 거동을 나타내었다.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.214.2-215
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• 2003

압출조리 공법에 의한 한국형 쌀 이유식 제조에서 아밀라제 첨가가 압출미분의 물성 변화에 미치는 영향을 알아보았다. 압출조리기의 스크류 회전수는 200rpm, 원료의 사입속도는 180g/min로 고정하여 작동하였다. 원료 쌀가루의 수분함량은 18, 23, 28%로 가수하였고 첨가된 아밀라제는 Bacillus licheniformis로부터 분리한 Termamyl 120LS(NOVO사), Bacillus amylolichuefaciens로부터 분리한 BAN 240L(NOVO사) 및 맥아분말이다. 아밀라제 첨가에 의해 압출미분의 수용성지수는 3배까지 증가했고, 환원당 생성량은 원료의 수분함량에 크게 영향을 받아 28% 수분함량에서 급격히 증가하여 수용성지수와는 다른 경향을 나타내었다. 겔 투과크로마토그래피에 의한 분자량적 구조 변화 측정 결과 아밀라제 첨가에 의해 고분자 획분이 상당히 감소했으며 상대적으로 저분자 획분이 증감함을 알 수 있었다. 아밀라제의 잔존환성은 아밀라제 종류에 따라 다르며 가장 내열성인 Termamyl 120LS의 경우 용융부위 온도 14$0^{\circ}C$에서 27%까지 감소하였다. 침전법에 의한 분산특성은 아밀라제 작용에 의해 수용성 물질이 증가함에 따라 침전층의 감소를 나타내었으나 처리온도가 14$0^{\circ}C$로 증가하면 침전층의 높이는 증가하였다. 겉보기 점도는 아밀라제 첨가에 의해 무처리 압출미분의 1/4~1/200로 감소하였다. 시판 이유식의 권장농도에서의 점도와 같은 점도 수준에 도달하기 위해서는 원료의 수분함량(18, 23, 28%), 아밀라제 종류 및 첨가량, 계량부위 온도에 따른 각 작동조건의 압출미분을 최고 1.8배의 양을 사용할 수 있었다. 이상에서 살펴본 바와 같이 원료 쌀가루에 첨가된 아밀라제가 압출조리기내를 통과하면서 쌀가루의 가수분해를 일으켜 환원당 등 수용성 물질이 증가하고 분산특성이 좋아지며 점도가 낮아지고 결국 이유식의 열량밀도를 증가시킬 수 있음을 확인할 수 있었다.

• Journal of Korea Foundry Society
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• v.26 no.5
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• pp.217-221
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• 2006

The main emphasis of this study was to utilize thixoextrusion process for improving extrudability of 7075, 7003 Al wrought alloys and AZ31 Mg wrought alloy. The results of thixbextrusion experiments about microstructures and extrusion pressures were compared with conventional hot extrusion results. The maximum extrusion pressure of thixoextrusion was greatly decreased compared with that of conventional hot extrusion. It was pointed out that the extrusion temperature dependence of the maximum extrusion pressure was large and the influence of extrusion temperature on the improvement of extrudability was remarkable in thixoextrusion. This will contribute to extrudability in terms of extrusion pressure, which in turn means that shorter process time is required and smaller extrusion machine can be applied for the same operation. The elongated grains to extrusion direction were generally observed during conventional hot extrusion, while the thixoextruded microstructures were isotropic.

• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.1036-1043
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• 1994

The silane crosslinking method was applied for the crosslinking of polyethylene (PE). Crosslinking of PE was performed by, first grafting vinyltrimethoxysilane(VTMOS) to the main chain of PE using an extruder at $200{\sim}210^{\circ}C$, followed by exposure to three different silane crosslinking conditions (1. immersed in $80^{\circ}C$ water, 2. at $80^{\circ}C$ air forced convection oven, 3. exposed to air at room temperature ). The thermal characteristic changes of PE resins with respect to the silane crosslinking conditions were studied by measuring the crystalline melting temperature, density and crosslinking reaction rate. Because silane crosslinking was carried out at solid state, crystalline melting temperature, crystallinity, crystal growth rate, crosslinking reaction rate and the change in the density of silane crosslinked PE were affected by crosslinking condition and the type of base resin. The properties of silane crosslinked PE were different from those of Peroxide crosslinked PE which was crosslinked at the molten state. It was found, from the result of DSC analysis, that silane crosslinked linear low density polyethylene(LLDPE) crosslinked at room temperature had no secondary melting peak because the crosslinking reaction proceeds slowly as the crystalline grows. After crystallization, the melting point of PE was lowered by crystalline interruption of crosslinked site.

• Korean Journal of Food Science and Technology
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• v.28 no.1
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• pp.169-178
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• 1996

Target parameters such as water solubility index (WSI), intrinsic viscosity (IV), water holding capacity (WHC), oil holding capacity (OHC), soluble dietary fiber (SDF) and microstructure were investigated on three different screw configurations during twin-screw extrusion of wheat bran. WSI of raw wheat bran (RWB) was 13.7%, while that of extrudates ranged $16.3{\sim}23.2%$ when extruded using screw configurations with 5 reverse screw elements (RSE). It was found that the moisture content of RWB greatly affected WSI of extrudates. IV of wheat bran extrudates increased from 10.6 ml/g of RWB to $37.86{\sim}44.37\;ml/g$ of extrudates extruded using 3, 4 and 5 RSE, whose trend was highly related to the moisture content of RWB and the extrusion pressure. Multiplication of IV and soluble solid (SS) content exhibited good correlation $(R^2=0.85)$ with specific mechanical energy (SME). The results suggested that SS and molecular size are an important factor governed by the SME in solubilization of wheat bran. WHC increased with increasing feed rate and moisture content, while OHC decreased. SDF increased from 2.68% of RWB to $4.32{\sim}6.48%$ of extruded wheat bran, indicating the significant breakdown of cell wall components. Microstructure of the extrudates showed the distinct patterns of degradation and solubilization of cell wall structure, depending on the moisture content of RWB.