• Polymer(Korea)
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• v.39 no.1
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• pp.180-184
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• 2015

PP-grafted GO was prepared by the reaction of graphene oxide (GO) containing 2-bromoisobuyryl groups and polypropylene (PP) having hydroxyl groups (PP-OH) via a "grafting-to" method. GO-Br was synthesized by the reaction of GO and 2-bromoisobutyryl bromide under a basic condition. PP-MAH was reacted with ethanolamine to produce PP-OH. The melting temperature of PP-grafted GO was shifted to the higher temperature than that of PP-OH. Also, the thermal stability of PP-grafted GO was increased as compared to PP-OH and GO. These results demonstrated that the grafted coating polymer PP was effective for enhancing the thermal stability of GO. The higher surface roughness of PP-grafted GO was resulted from the chemical attachment of PP on the surface of GO. The characterization of PP-grafted GO was conducted from Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscope (SEM).

• The Journal of the Korea Contents Association
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• v.13 no.2
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• pp.71-80
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• 2013

This study addressed status of PP(Program Provider) market, particularly focusing on independent PP. This research selected 14 independent channels and did in depth interviews for them. This study analyzed 14 channels in terms of management, production, and contents. The result showed that independent channels were in inferior condition than MPP(multiple PP) on all the aspects of management, production and content. The management structure of the PP were very vulnerable, production environment was not good. The PP were placed in a difficult environment in terms of production and purchases of content, therefore focused on distribution rather than production. This unbalance on the PP market resulted in negative effect on Korea's contents industry as well as PP industry. Therefore, this study suggested policy and regulatory reforms are needed to improve inferior status of independent PP.

• Elastomers and Composites
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• v.49 no.3
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• pp.225-231
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• 2014

In this study, we used polypropylene grafted with itaconic acid (PP-g-IA) as a compatibilizer to prevent phase separation phenomenon which occurs upon blending polypropylene (PP) and ethylene-vinyl alcohol copolymer (EVOH). A compatibilizer was prepared using graft copolymerization of itaconic acid (IA) onto PP where input ratio of IA was 1, 2, 5, and 10 wt.%. To confirm the structure of PP-g-IA and the graft ratio of IA onto PP, we used $^1H$ NMR and FT-IR. We tested the compatibilizer which has highest graft ratio of 1% in immiscible PP/EVOH blends. The morphologies of PP/PP-g-IA/EVOH blends were analyzed by SEM. Thermal and mechanical properties of the blends were analyzed by DSC and UTM. PP-g-IA enhanced the interfacial adhesion of PP and EVOH copolymer.

• Polymer(Korea)
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• v.38 no.5
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• pp.566-572
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• 2014

Maleic anhydride (MAH) grafted polypropylenes (PP) (MAH-g-PP) were prepared by changing MAH content and styrene monomer (SM)/MAH mole ratio with different type PP, using a twin screw extruder. The types of PP were isotatic PP (iPP), block PP (bPP), and random PP (rPP) and dicumyl peroxide (DCP) was used as an initiator. The graft degree of MAH was confirmed by the existence of carbonyl group (C=O) stretching peak at $3100cm^{-1}$ of FTIR spectrum. Thermal properties of MAH-g-PP and PP/MAH-g-PP/pulp composites were investigated by DSC and TGA. There was no district change in thermal properties of PP/MAH-g-PP/pulp composites. Based on tensile properties and SEM pictures for fractured surface of PP/MAH-g-PP/pulp composites, MAH-g-rPP was the best as the compatibilizer and optimum formulation was MAH content of 1.0 wt%, SM/MAH mole ratio of 1.0, and melt index (MI) of 25 g/10 min. The rheological properties of the composites were investigated by a dynamic rheometer. The complex viscosity, shear thinning effect, and water uptake incresed with pulp content.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1125-1129
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• 2008

Polypropylene (PP)/corn starch master batch(starch-MB) blends with different PP compositions of 90, 80, 70, and 60 wt% were prepared by melt compounding at $200^{\circ}C$, using lab scale Brabender mixer. The chemical structures, thermal properties and non-isothermal crystallization behavior of the PP/starch-MB blends were investigated by FT-infrared spectrometry (FT-IR), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). The fabrication of the PP/starch-MB blend was confirmed by the existence of hydroxy group in FT-IR spectrum. There was no district change in melting temperature and melting enthalpy, and TGA curve indicates a decrease in degradation temperature with starch-MB content. The non-isothermal crystallization process was analyzed using by Avrami equation. The Avrami exponents were in the range of 2.71-3.97 for PP and 1.48-1.99 for PP/starch-MB blonds. The activation energies calculated by Kissinger method were 233 kJ/mol for PP, 484 kJ/mol for PP90, 541 kJ/mol for PP80, 553 kJ/mol for PP70, and 422 kJ/mol for PP60.

• Molecules and Cells
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• v.42 no.7
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• pp.546-556
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• 2019

Protein phosphatase 4 (PP4) is a crucial protein complex that plays an important role in DNA damage response (DDR), including DNA repair, cell cycle arrest and apoptosis. Despite the significance of PP4, the mechanism by which PP4 is regulated remains to be elucidated. Here, we identified a novel PP4 inhibitor, protein phosphatase 4 inhibitory protein (PP4IP) and elucidated its cellular functions. PP4IP-knockout cells were generated using the CRISPR/Cas9 system, and the phosphorylation status of PP4 substrates (H2AX, KAP1, and RPA2) was analyzed. Then we investigated that how PP4IP affects the cellular functions of PP4 by immunoprecipitation, immunofluorescence, and DNA double-strand break (DSB) repair assays. PP4IP interacts with PP4 complex, which is affected by DNA damage and cell cycle progression and decreases the dephosphorylational activity of PP4. Both overexpression and depletion of PP4IP impairs DSB repairs and sensitizes cells to genotoxic stress, suggesting timely inhibition of PP4 to be indispensable for cells in responding to DNA damage. Our results identify a novel inhibitor of PP4 that inhibits PP4-mediated cellular functions and establish the physiological importance of this regulation. In addition, PP4IP might be developed as potential therapeutic reagents for targeting tumors particularly with high level of PP4C expression.

• Macromolecular Research
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• v.15 no.4
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• pp.308-314
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• 2007

The effects of a compatibilizer on polypropylene (PP)/poly(acrylonitrile-butadiene-styrene) (ABS) blends were studied. Blends of the PP/ABS, with PP-g-SAN copolymer as a compatibilizer, were prepared using a twin screw extruder. The flexural and impact strength of the PP/ABS blends with the PP-g-SAN copolymer increased significantly with PP-rich compositions on the addition of the PP-g-SAN copolymer at 3 phr. The increase in the mechanical properties of the PP/ABS/PP-g-SAN blend may have been due to the toughening effects of the ABS in the PP-rich compositions. In the morphology study of the PP/ABS/PP-g-SAN (80/20) blend with the PP-g-SAN copolymer, the minimum droplet size, $5.1{\mu}m$, was observed with the addition on phr of the PP-g-SAN copolymer. The complex viscosity of the PP/ABS/PP-g-SAN (80/20) blends increased with the addition of3 phr of the PP-g-SAN copolymer. From the above mechanical properties, morphology and complex viscosity results for the PP/ABS blends, it is suggested that the compatibility is more increased with the PP-rich composition (PP:ABS=80/20 wt%) of the PP/ABS blend on the addition of 3 phr of the PP-g-SAN copolymer.

• Polymer(Korea)
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• v.32 no.1
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• pp.7-12
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• 2008

We confirmed that poly (ethylene terephthalate) (PET) fiber had the possibility to improve the mechanical properties of polypropylene (PP) by fabricating PP/PET fiber composites because PET enhanced mechanical properties and higher melting temperature than PP. But lower compatibility of between PP and PET fibers induced poor mechanical properties of PP/PET fiber composites in spite of incorporating PP-g-MAH as compatibilizer. To solve these problems of PP/PET fiber composites, we carried out a surface treatment on PET fiber using NaOH solution and Prepared PP/PET fiber composites with good mechanical properties by adding PP-g-MAH as a compatibilizer Then the behavior of the mechanical properties was correlated with the results obtained from SEM and IR spectroscopy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1988-1992
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• 2011

Polypropylene (PP)-SEBS/silicate composites with PP content of 35, 40, and 45wt% were fabricated by melt compounding at $200^{\circ}C$, using lab scale Brabender mixer. The content of silicate was fixed at 5wt%. The thermal properties of the PP-SEBS/silicate composites were investigated by differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). The melting temperature of PP-SEBS compound decreased up to $141^{\circ}C$ with SEBS content. TGA result indicates an increase in degradation temperature when the silicate was added in the PP-SEBS compound. The rheological properties of the compounds were measured by dynamic Rheometer. PP-SEBS/silicate composite indicates higher shear thinning and elastic property than PP-SEBS compound. Van Gurp-Palmen analysis was applied in order to certify an increase in elasticity.

• The Korean Journal of Rheology
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• v.10 no.1
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• pp.14-23
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• 1998

비상용성 고분자 브렌드계인 PS/PP와 EPDM/PP의 유변학적 거동에 미치는 계면의 영향을 알아보았고 그실험 결과를 Park & Lee 모델과 비교하였다. PS/PP와 EPDM/PP 블 렌드계에서의 계면에 의한 전단응력과 법선 응력차에의 기여도는 $textsc{k}$와λ(1-$\mu$), 두 개의 변 수에 의해 잘설명되었다. 특히 계면의 탄성적인 효과와 관련있는 법선응력차 항이 전단 응 력 항보다 더 뚜렷하게 나타났다. 30PS/70PP 블렌드 조성에서는 블렌드의 유변학적 특성이 주로 연속상을 이루는 고분자의 의해 좌우된 반면에 50PS/50PP 블렌드조성에서는 계면에 의한 영향이 더두드러지게 나타났다. 이것은 50/50 블렌드 조성에서 계면의 넓이가 증가한 것과 관계 있다. 그러나 EPDM/PP 블렌드계에서 계면에 의한 응력 항들이 모두 PS/PP 블 렌드계의 그것보다 매우 큰 값을 가졌지만, 그 상대적인 비를 나타내는 $textsc{k}$값은 작았다. 이것 은 블렌드를 구성하고 있는 순수한 성분의 법선응력차 값의 차이가 크기 때문이다. 또한 PS/PP 블렌드계에 대한 동적 계면장력을 Park & Lee 모델을 이용하여 예측해 보았다.