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Flow Marks of Polypropylene (PP) Composites in the Injection Molding
정현택,김용렬 한국응용과학기술학회 2015 한국응용과학기술학회지 Vol.32 No.2
Flow mark is a sort of surface defect on the composite that can arise during the filling stage of the injection molding process. The purpose of this study is to clarify a mechanism of the flow mark which appears on the surface of injection molded Polypropylene (PP) through the characterization of the surface structure. The materials used in this report are PP/rubber and PP/talc compounding, which are widely used in automobile part. The flow mark shows two different constitutions, such as a luster part and a cloud part on the surface of the injection molded PP. We have investigated the surface structure of PP/rubber and PP/talc composites by using scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDAX) and optical microscopy (OM). As a result, the cloud part contains higher contents of the rubber and talc compare to the luster part.
Highly flexible dielectric composite based on passivated single-wall carbon nanotubes (SWNTs)
정현택,김용렬 한국응용과학기술학회 2015 한국응용과학기술학회지 Vol.32 No.1
Single-walled carbon nanotubes (SWNTs) was modified with various length of linearalkyl chains and passivated to form dielectric filler. The modified SWNTs embedded into epoxymatrix to fabricate a flexible composite with high dielectric constant. The dielectric behavior of thecomposite was significantly changed with various alkyl chain length(n) of pyrene. The dielectricconstant of the epoxy/SWNTs composite significantly increased with respect to increase in length ofalkyl chain at the frequency range from 10 to 105Hz (n=12and18).We also found that thepassivated epoxy/SWNTs composite with high dielectric constant presented low dielectric loss. Theresulted dielectric performances corresponded to de-bundling of nanotubes and their distributionbehavior in the matrix in terms of tail length of alkyl pyrene in the passivation layer.
정현택 한국탄소학회 2020 Carbon Letters Vol.30 No.1
The reduced graphene oxide/single-wall carbon nanotubes composites are coated onto the polyurethane substrate using spray coating technique to produce a stretchable and semi-transparent supercapacitor. The electrochemical properties of the stretch�able and semi-transparent full device as a function of stretching cycles are characterized using electrochemical impedance spectroscopy (EIS), cyclic voltammetry and galvanostatic charge/discharge tests. The EIS and charge/discharge curves of the stretchable and semi-transparent supercapacitor exhibit good capacitive behavior even after prolonged stretching cycles up to 100. The highest capacitance value of the stretchable and semi-transparent supercapacitor (unbent) is 21.4 F g−1. The capacitance value of the stretchable and semi-transparent supercapacitor is retained 62% after 100th stretching with applica�tion of 3000th galvanostatic charge/discharge cycles.