• Korea-Australia Rheology Journal
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• v.19 no.3
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• pp.133-139
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• 2007

Low density polyethylene nanocomposites were prepared by melt intercalating maleic anhydride grafted polyethylene and montmorillonite clay. It has been found that maleic anhydride has promoted strong interactions between polyethylene and montmorillonite, leading to the homogeneous dispersion of clay layers. Rheological experiments revealed that prepared nanocomposites exhibited shear thinning behaviour. Polyethylene nanocomposites exhibited an increase in steady shear viscosities compared to virgin polyethylene owing to strong polymer clay interactions. The tensile strength of nanocomposites was improved but elongation at break decreased considerably. Also, barrier properties improved significantly with montmorillonite content.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.1-6
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• 2023

PE piping, which has advantages in terms of construction convenience and economy, is widely used for underground burial in the domestic urban gas field. These PE pipes use squeeze-off in many sites to block gas flow during maintenance and repair work. Squeeze-off refers to a method of compressing a PE pipe to block fluid flow, and damage may occur due to the nature of construction in which the pipe is deformed by physical force. In order to prevent damage to PE pipes due to squeeze-off, the main points to be reflected in the squeeze-off operation procedures such as proper compression range, use pressure, and diameter were derived through damage assessment and confidential test according to the compression rate. The compression experiment for PE pipe damage assessment was conducted while changing the compression rate (20%~40%), the pressure of use (2.8 kPa, 25 kPa, 70 kPa), and the pipe diameters (63 mm, 90 mm, 110 mm). As a result of damage assessment according to the compression rate, damage occurred in pipes with compression rates of 45%(110mm) and 73%(63mm), which are for analyzing the effect of excessive compression. In addition, the leakage test was conducted using Ar(argon) during the squeeze-off, and as a result of the experiment, leakage occurred under the conditions of 70kPa and 110mm of pipe. As a result of this study, it was confirmed that squeeze-off for airtightness should be carried out in pipes within a range not exceeding 25 kPa and 90 mm pipes, and the appropriate compression rate to prevent damage to PE pipes is 30%.

• Polymer(Korea)
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• v.34 no.1
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• pp.74-78
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• 2010

In this paper, crosslinked polyethylene (PE) separators for lithium secondary batteries were prepared by an electron beam irradiation under various beam currents and dose rates. The crosslinking degree increased up to maximum 71% with an increasing absorption dose and with a decreasing beam current. The PE separators irradiated at lower beam currents showed better thermal shrinkage (51%) and mechanical properties than the original PE separator and PE separators irradiated at higher beam current. The ionic conductivity ($1.01{\times}10^{-3}\;S/cm$) and electrolyte uptake (275%) of the crosslinked PE separators were comparable to the original PE separator.

• Journal of Bio-Environment Control
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• v.23 no.4
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• pp.314-320
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• 2014

Three leaf vegetables, namely green lettuce, red lettuce (Lactuca sativa) and red-veined chicory (Cichorium intybus) were grown in minigreenhouses covered with two new functional films and conventional polyethylene film (PE). Seedlings of leaf vegetables were transplanted in a plastic troughs filled with soil-perlite mixture. Two functional films were made from polyolefin (PO) material. Measurement of optical characteristics showed that polyolefin films have better transmittance for the photosynthetic active radiation (PAR, 400-700nm) and higher absorptance for the ultraviolet radiation (UV, 300-400nm) in comparison with the conventional PE film. After three months of utilization higher loss in PAR transmittance was observed for conventional PE film. Leaf vegetables growth was enhanced and yield was increased in greenhouses covered by new functional films.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.3
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• pp.331-338
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• 2008

Coal-tar enamel, blown asphalt and polyethylene have been used as wrapping materials of steel pipe in Korea. Currently, every manufacturer produces wrapped steel pipes with different materials and methods, and little research has been performed to get on wrapping methods and materials. In this research, properties of wrapping material of steel pipe used for water supply have been evaluated. All of the materials tested in this work were found to meet the standard. Among the wrapping materials of steel pipe tested, blown asphalt and coal-tar enamel were reasonable in price, and their mechanical properties were excellent. The quality of the wrapped steel pipes was being melted easily in organic solvent. When coated thick, the load of the steel pipes was higher than necessary. Tensile strength of cathode exfoliation and PE 3-layer wrapping method was excellent. The pulling intensity of T-Die PE 3-layer was stronger than PE fluidized in PE wrapping method. Cathode exfoliation area was smaller than PE fluidized. Mechanical property and thermo-property of T-Die PE 3-layer were excellent and its anti-chemical property was great. Liquid epoxy can change the property of coating materials depending on the hardening condition and resin selection. Polyurethane used in this test showed a less adhesive strength with steel pipes than epoxy. Moisture absorbance rate was higher than Epoxy's, however. To utilize polyurethane as wrapping materials, basic property of the matter should be improved followed by finding the best suited coating condition. The method of PE 3-layer by extrude method appeared to be the best in this study. However, identification of other wrapping materials requires further additional tests.

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.670-678
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• 2017

Self-emulsifiable polyethylene (PE) wax was prepared using acrylic acid grafted PE wax with potassium hydroxide and various emulsifiers for the economic production of PE wax emulsion. Modification reaction completion was confirmed that the peak from carbonyl group of acrylic acid disappeared and the new peak from carboxylic acid salts appeared in the FT-IR (Fourier transform infrared) spectrum data. Self-emulsifiable properties of the modified PE wax were investigated by the emulsion size and the stability of wax emulsion without any additional emulsifiers. According to self-emulsifiable properties, the emulsion size and stability were varied on the concentration and structure of the emulsifier. The greater emulsion concentration and hydrophilic poly(ethylene oxide) (PEO) characteristics of the emulsifier resulted in the smaller emulsion size and better emulsion stability. In addition, the use of emulsifiers mixture was more effective to obtain smaller size and uniform distribution of emulsion than that of single emulsifier in PE wax modification reaction. Especially, modified PE wax with OAE-5 and LAE-15 emulsifiers mixture shows excellent performance in terms of the smallest emulsion size ($4.34{\mu}m$) and emulsion stability.

• Elastomers and Composites
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• v.38 no.4
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• pp.316-325
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• 2003

The blends of waste-polyethylene (W-PE)/waste-ethylene vinyl acetate copolymer (W-EVA) with inorganic and phosphorous flame retardants (i.e., aluminium hydroxide, magnesium hydroxide, and so on) were prepared by melt mixing techniques at different compositions and foamed. The flame retardancy and foaming properties of the blends, limiting oxygen index (LOI), heat release rate (HRR), carbon monoxide yield (COY), total heat release (THR), effective heat of combustion (EHC), expandability and cell structure were investigated using cone calorimeter, SEM, LOI tester and polarizing microscope. When the composition ratios of the W-PE/W-EVA blends were 50/50 (w/w), and the ranges of the flame retardants contents were $175{\sim}220 phr$, we could obtain foams with the uniform and closed cell, high expandability (1900 % or more), high LOI, and low HRR values. These results depend on crosslinking and loaming conditions, a char formation and smoke suppressing effect. Aluminium hydroxide had more effect in the increase of LOI than magnesium hydroxide, while magnesium hydroxide considerably affected the decrease of HRR and COY.

• Korean Journal of Weed Science
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• v.8 no.3
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• pp.317-323
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• 1988

This survey was conducted to know characterization of weed occurrence under protected culture conditions at Yousong in 1985. Chenopodium album, Polygonum hydropiper, Portulaca oleracea and Digitaria sanguinalis were dominated in outdoor, whereas Capsella bursa-pastoris, C. album, D. sanguinalis and P. oleracea were dominant in polyethylene house. More weeds emerged in mulching plots and dry weight of weeds was greater in non-mulching plots. Summer broadleaf weeds and summer grasses were abundant in outdoor, whereas non-mulching plots in polyethylene house was dominated by winter broadleaf weeds, and mulching plots in polyethylene house were dominated by winter grasses and winter broadleaf weeds in early stage and summer grasses and summer broadleaf weeds in late stage. Simpson index was high in polyethylene house and Shannon's diversity index, maximum diversity for the Shannon diversity index were lower than eveness using the Shannon diversity index and this trend was more remarkable in mulching and mulching in tunnel than in non-mulching under polyethylene house condition. Shannon diversity index, maximum diversity for the Shannon diversity index were high in mulching or tunnel, and Simpson index was high in non-mulching in outdoor condition. Interspecific competition was more severe than intraspecific competition in both conditions.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.1
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• pp.78-84
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• 1993

This study was conducted to investigate the effect of various polyethylene (PE) film packaging on the quality of strawberry during storage at low temperature. Gas composition in film was changed rapidly at early stage of storage and then kept at the level of 5~10% $CO_2$and 1~3% $O_2$. Weight loss and decay rate were low at 0.08mm PE film packed strawberries. Titratable acidity, pH and soluble solids were changed slightly during storage but its large difference according to film thickness was not observed. Decrease of flesh firm-ness and a value was restrained by PE film packaging. Free sugar of strawberry was composed of glucose and fructose in similar content and it was decreased a little during storage but the difference according to film thickness was not observed. The organic acids in strawberry were citric acid, malic acid, succinic acid, ascorbir acid, oxalic acid, tartaric acid and pyruvic acid and the major organic acid was citric acid. The contents of citric acid, malic acid, succinir acid and ascorbic acid were decreased and oxalic acid and tartaric arid were not changed during storage but pyruvic acid was increased in early stage and then decreased. These changes of organic acid were slight in packaged with 0.08mm PE film strawberry.

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.153-161
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• 2007

This paper investigates the lap splice performance of structural steel bars embedded in high performance fiber reinforced cementitious composite(HPFRCC) with various matrix ductilities. Matrix ductility is governed fiber type and fiber volume fraction. Fiber types were polypropylene(PP), polyethylene(PE) and hybrid fiber[polyethylene fiber+steel cord(PE+SC)]. The lap splice length$(l_d)$ was calculated according to the relevant ACI code requirements for reinforcing bars in normal concrete. As the result of tests, lap splice strength of HPFRCC using PE1.5 and hybrid fiber increased by up to $82{\sim}91$ percent more than that of concrete. Splice strength and energy absorption capacity of PE0.75+SC0.75 or PE1.5(fiber volume fraction 1.5%) specimen increased more than that of PP2.0(fiber volume fraction 2.0%) specimen. Therefore lap splice performance depends on fiber tensile strength and Young's modulus more than fiber volume fraction. Also, HPFRCC appear multiple crack and ductile postpeak behavior due to bridging of fiber in cementitious composite.