• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.1
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• pp.51-60
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• 2010

Recently, a new type of polyolefin fiber having a good mechanical properties is being developed, and it is necessary to examine a possibility for the new fiber together to be used as a reinforcing fiber with other types of fiber or by itself. The objective of this study is to find flexural toughness and tensile strength of concrete reinforced with steel and polyolefin fibers. Four point beam tests were performed with 324 specimens following two standard tests methods: KS F 2566 and ASTM C 1399-02. From the test results, the effects of volume fraction of fibers, and aspect ratio of steel fiber on the toughness and tensile strength were investigated, and the optimal ratio of steel fiber to polyolefin fiber was suggested.

• Polymer(Korea)
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• v.29 no.4
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• pp.321-330
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• 2005

In 1990's the Korean polyolefin industry boomed up through the development of magnificient polymerization catalysts. To understand the general situation of polymerization catalyst R & D, the various experimental results had been summarized for the investigation of not only the supported Ziegler-Natta catalyst used presently in polyolefin industry but also the metallocene catalysts applied for the preparation of special grade of polyolefin. In addition, it had been shown that the new polymeric materials were prepared by new developed catalyst, and the polymer in-situ nanocomposites could be obtained with the application of catalyst heterogenization procedures.

• Korean Chemical Engineering Research
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• v.44 no.4
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• pp.329-339
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• 2006

The production of lower olefins from methanol becomes an attractive process because of the rapid increase in crude oil price. This paper reivews the conversion mechanisms of methanol to hydrocarbons over zeolite and SAPO molecular sieve catalysts to understand the formation steps of lower olefins from methanol. The feasibility of the conversion mechanisms such as the direct mechanism based on well-defined intermediates and the hydrocarbon pool mechanism involving hydrocarbon moieties as an active centers is discussed with reepect to the induction period, the selectivity for products and the deactivation phenomena of the methanol conversion. The literature appeered since 1999 for the structure of the hydrocarbon pool and its catalytic role in the methanol conversion are summariged, and the prospect for the methanol-to-olefins process is described.

• Korean Chemical Engineering Research
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• v.44 no.4
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• pp.345-349
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• 2006

Conversion of DME (dimethyl ether) or methanol to light olefins (ethylene, propylene, butenes) over SAPO-34 were systematically studied, where it was observed that DME was dehydrated to light olefins and partially converted to by-products such as CO and $CO_2$ at various reaction temperatures on the time-on-stream. SAPO-34 catalyst during the DTO (dimetyl ether-to-olefins) reaction was significantly deactivated compared with MTO (methanol-toolefins) reaction. By addition of water to the reaction feed, the yield to light olefins was not only increased, but the life time of the catalyst was also prolonged by the suppression of the coke formation by steam.

• Polymer Science and Technology
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• v.5 no.3
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• pp.236-253
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• 1994

양이온형 $d^0\;Cp_2M(R)(L)^+$ 착물과 무염기 $Cp_2M(R)^+$ 착물은 $Cp_2M(R)_2$화합물로부터 쉽게 합성할 수 있다. 이들 친전자성 착물에서는 여러가지 리간드 교환반응, 삽입반응, ${\beta}$-H 제거반응 및 ${\sigma}$-결합 복분해반응이 일어날 수 있다. 일반적으로 $Cp2M(R)(L)^+$ 착물은 불포화도와 전하가 크기때문에 중성의 $Cp_2M(R)(X)$나 $Cp_2M(R)_2$보다 반응성이 크며 $d^0\;{Cp_2}^*M(R)^+$ (M=제 3족과 란탄계) 착물과 여러가지 반응에서 유사한 거동을 보인다. $Cp_2MX_2$를 기초로하여 합성된 Ziegler-Natta 촉매에 의한 올레핀 중합에서 활성점이 $Cp_2M(R)^+$ 양이온이라는 여러가지 직접적인 증거가 발표되었다. 분리가능한 $Cp_2M(R)(L)^+$ 착물은 올레핀중합에서 높은 활성을 보이며, 유기합성의 관점에서 흥미있는 C-C 재조합반응과 같은 다른 여러가지 반응이 일어날 수 있는 기회를 제공한다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.3
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• pp.246-254
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• 2013

This study is purposed to verify the safety of the floor of the children's playground using polyolefin foam waste and rubber paving. The critical fall height, walking suitability, long term physical fatigue expectation and slipperiness were tested. Polyolefin foam wastes in thickness of 30mm, 50mm and 70mm were prepared with paving the rubber paving materials in 12mm and 15mm thickness respectively. The test on the critical fall height was carried out according to KS G 5758:2009. The floor hardness test equipment (O-Y HMA) was used for the test on hardness of the floor from a viewpoint of walking suitability and fatigue. A portable slipperiness tester (ONO PPSM) was used for slipperiness test. It was revealed from the test that the floor made of the polyolefin foam waste and rubber paving were considerably safe from a viewpoint of impact absorption. With regards to the hardness of the floor, it was shown the excellent performance in the aspects of walking and fatigue for male. But it was not suitable with walking on the shoes(middle heels) for female. And they will be very fatigue if they were in a long time walking or standing. As far as the slipperiness is concerned, it was shown that it was comparatively safe for the ordinary motions even though the surface was wet.

• Polymer(Korea)
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• v.24 no.5
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• pp.646-655
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• 2000

Polymerizations of higher $\alpha$-olefins were carried out in toluene by using highly isospecific catalyst, rac-(EBI)M(NMe$_2$)$_2$ (EBI=1,2-ethylenebis-(1-indenyl); M=Zr(rac-1); M=Hf(rac-2)) In the presence of Al(i-Bu)$_3$/[Ph$_3$C][B($C_{6}F_{5}$)$_4$]. The polymerization of high $\alpha$-olefin showed high activity and similar polymerization behavior. The polymerization activity was affected by both monomer size and lateral size of polymer chain. The conversion of monomer to polymer decreases with the increased lateral size in the order of 1-pentene>1-hexene>1-octene>1-decene. The same dependences of melting behavior and intrinsic viscosity of polyolefin on lateral size were observed according to the results obtained by differential scanning calorimetry and intrinsic viscosity. All poly($\alpha$-olefin)s showed very high isotacticity (triad) and the isotacticity increases in the order of poly(1-pentene)$^1H$ NMR and Raman spectra analysis showed that chain transfer to cocatalyst, which generates saturated methyl groups, Is a main chain termination. The $\beta$-hydride eliminations, which generate unsaturated vinylidene, tri-substituted, and vinylene end group. are found to be minor chain terminations.

• Membrane Journal
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• v.25 no.6
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• pp.496-502
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• 2015

Facilitated transport is one of the possible solutions to simultaneously improve permeability and selectivity, which is challenging in conventional polymer-based membranes. Olefin/paraffin separation using facilitated transport membrane has received much attention as an alternative solution to the conventional distillation process. Herein, we report olefin separation composite membranes based on the polymer blends containing $AgBF_4/Al(NO_3)_3$ mixed salts. Free radical polymerization process was used to synthesize an amphiphilic graft copolymer of poly(dimethyl siloxane)-graft- poly(ethylene glycol) methyl ether methacrylate (PDMS-g-POEM). In addition, poly(ethylene oxide) (PEO) was introduced to the PDMS-g-POEM graft copolymer to form polymer blends with various ratios. The propylene/propane mixed-gas selectivity and permeance reached up to 5.6 and 10.05 GPU, respectively, when the PEO loading was 70 wt% in polymer blend. The improvement of olefin separation performance was attributed to the olefin facilitating silver ions as well as the highly permeable blend matrix. The stabilization of silver ions in the composite membrane was achieved through the introduction of $Al(NO_3)_3$ which suppressed the reduction of silver ions to silver particles.

• Polymer Science and Technology
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• v.12 no.3
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• pp.344-350
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• 2001

• Proceedings of the Membrane Society of Korea Conference
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• 2003.05a
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• pp.7-13
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• 2003