• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.679-684
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• 2011

Branched polypropylenes (LCB-PP) with a long chain branch were prepared by the solid-state and molt-state reaction. Divinylbenzene (DVB), 1,4-benzenediol (RES), and furfuryl sulphide (FS) were used as branching agents of fabricate LCB-PP/silicate composites. Chemical structures, thermal properties, and rheological properties of the LCB-PP were determined by FT-IR, DSC, TGA, and dynamic rheometer (ARES). The chemical structure of the LCB-PP was confirmed by the existence of =C-H stretching peak of the branching agent at $3100cm^{-1}$. From DSC and TGA results, the melting reaction was more effective than the solid state reaction in the manufacture of LCB-PP, which was additionally certified by rheological properties. Based on rheological properties, FS was the best for branching efficiency of PP. Compared to PP, LCB-PPs indicated an increase of complex viscosity in the low frequency and shear thinning tendency, and G'-G" plot represented an increase in elasticity and the heterogeneousness in a melt state. Rheological properties of LCB-PP/silicate composites were observed with the silicate content. When 5 wt% silicate was added in LCB-PP, distinct changes in the shear thinning and the slope of G'-G" plots were observed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4261-4266
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• 2011

Polypropylene (PP)/talc compounds with talc content of 20wt% were fabricated by master-batch (MB) and direct compounding method using injection molding. The MB was prepared by mini compounder at $200^{\circ}C$ and the content of talc was 50wt%. The talc dispersion of the PP/talc compound was investigated by SEM-EDS. The talc was well dispersed within PP matrix in case of the MB-PP compound using MB. The rheological properties of the PP/talc compounds were measured by dynamic Rheometer. The MB-PP compound indicates higher shear thinning and elastic property than direct compound. The disperion of talc was certified by G'-G" plot, and Van Gurp-Palmen analysis was applied in order to certify an increase in elasticity.

• The Korean Journal of Applied Statistics
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• v.20 no.3
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• pp.585-595
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• 2007

The squared Euclid distance of the values which is transformed by P-matrix of Ahn et al. (2003) is in proportion to the squared Euclid distance of cell's relative frequencies in two Contingency Tables. We propose the method of using the PP-values for the analysis of modern poems and questionnaire data.

• Composites Research
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• v.37 no.4
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• pp.325-329
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• 2024

To accurately predict airbag deployment during a collision, the mechanical properties of polymer materials at high strain rates according to temperature should be considered. In this study, the mechanical properties of TPO and polypropylene were measured at high strain rates via split-Hopkinson pressure bar tests under various environmental temperatures ranging from -35 to 85℃. Through this, tensile strength and failure strain were derived for each strain rate. As the polymer phase moves toward the high strain rate region, the β-transition becomes dominant, resulting in a non-linear increase in tensile strength in the Eyring plot. Additionally, an airbag module impact simulation was conducted to verify the effects of strain rate on airbag deployment using the LS-DYNA software. It was found that the TPO and polypropylene airbag deployment could be accurately predicted using the strain-rate-dependent mechanical behavior rather than quasi-static properties alone.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.867-873
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• 2007

Thermal degradation characteristics of polypropylene and polystyrene have been studied in the thermogravimetric(TG) reactor and batch-type microreactor. The dynamic thermogravimetric curve of TG provided a valuable information about pyrolysis temperature. It was found that PS was thermally degraded at lower temperature of $30{\sim}50^{\circ}C$ than PP. It was found that the yield and molecular weight of liquid product in the microreactor were decreased with the increase of reaction temperature and time in the case of PP. The production of styrene monomer was significantly increased by the promotion of depolymerization with the increase of temperature and time. The chain-end scission rate parameters were determined to be 50.0 kcal/mole of PP, 45.2 kcal/mole of PS by the Arrhenius plot.

• Textile Coloration and Finishing
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• v.9 no.6
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• pp.18-25
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• 1997

The change of crystalline structure and mechanical properties of i-PP films which had before isothermally annealed at various temperature and times have been studied. The following results were abtain The crystallinity and crystallite size of the samples showed increasing above the annealing temperature of 13$0^{\circ}C$ and these are equilibrated after an annealing time of 30min. When the crystalline form was at annealling condition were below 13$0^{\circ}C$, 2min, subsequently achieving an $\alpha$, $\beta$ mixing form and at 13$0^{\circ}C$, 10min, the crystalline form entered an $\alpha$ form transition. It is achieved a typical $\alpha$ form at 15$0^{\circ}C$. The value of T'm was increasing until 13$0^{\circ}C$ but it was not founded at 15$0^{\circ}C$. The slopes which represented crystalline form in an Avrami plot differed from each other within the range of this experiment.

• Journal of Korean Society for Quality Management
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• v.25 no.4
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• pp.88-98
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• 1997

For quality improvement, it is important to reduce variations of the quality characteristic. That can be achieved by the a, pp.ication of parameter design methodology to make the performance of the quality characteristic robust over the variety of noise conditions. Taguchi has used the signal-to-noise ratios for that purpose. For the static target characteristic and the dynamic characteristic problem, we propose a reasonable generalized SN ratio and p-value plot for identifying dispersion factors. The orginal idea of the p-value plot in from the gamma-plot in Lunani, Nair & Wasserman(1995). The graphic advantage of the p-value polt for identifying dispersion factors is illustrated through constructed examples.

• Korea-Australia Rheology Journal
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• v.17 no.1
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• pp.21-25
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• 2005

Rheological properties and crystallization kinetics of the polypropylene (PP) block copolymer and recycled PP block copolymer were studied by advanced rheometric expansion system (ARES), differential scanning calorimetry (DSC), and optical microscopy. In the study of the dynamic rheology, it is observed that the storage modulus and loss modulus for the PP block copolymer and recycled PP block copolymer did not change with frequency. In the study of the effect of the repeated extrusion on the crystallization rate, half crystallization time of the PP samples was increased with the number of repeated extrusion in isothermal crystallization temperature ($T_c$). From the isothermal crystallization kinetics study, the crystallization rate was decreased with the increase of the number of repeated extrusion. Also, from the result of Avrami plot, the overall crystallization rate constant (K) was decreased with the increase of the number of the repeated extrusion. From the study of the optical microscopy, the size of the spherulite of the PP samples did not change significantly with the number of repeated extrusion. However, it was clearly observed that the number of the spherulite growth sites was decreased with the number of repeated extrusion. From the results of the crystallization rate, isothermal crystallization kinetics, Avrami plots, and optical microscopy, it is suggested that the crystallization rate of the PP block copolymer is decreased with the increase of the number of repeated extrusion.

• Journal of Korean Society for Quality Management
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• v.25 no.1
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• pp.100-115
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• 1997

Shewhart control chart is a basic technique to monitor the state of a process. We observe samples of size four or five and plot some statistic(e.g., mean or range) of each sample on the chart. When setting up the chart, we need to obtain u, pp.r and lower control limits. It is common practice that those limits are calculated from the preliminary 20-40 samples presumed to be homogeneous. However, it may ha, pp.n in practice that the samples are contaminated by outlying observations caused by various reasons. The presence of outlying observations make the control limits wider and hence decrease the sensitivity of the charts. In this paper, we introduce robust control charts with tighter control limits when outlying observations are present in the preliminary samples. Examples will be given via simulation study.

• Korean Journal of Plant Resources
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• v.7 no.1
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• pp.1-5
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• 1994

To decrease the bolting rate of Angelica gigas, The growth inhibitors such as MH, Pp333 (paclobutrazol) and CCC(chloroniequat or Cycocel) were treated twice with the interval of 20 days atthe forming stage of flower bud.Growth and bolting rate in plot treated inhibitors were retarded and decreased, and the yield ofroots was also decreased compared with non - treatment. The treatments of MH and Pp333 amongthree inhibitors showed the better effects in decreasing the bolting than that of CCC, but they did notshow the significant in the yield and contents of decursin among each of them.In order to improve the decreasing effects by chemicals, selection of suitable reagents, concentrationand number of treatment should be investigated.