• Composites Research
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• v.33 no.5
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• pp.282-287
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• 2020

In the present study, a high-strength polyethylene terephthalate (PET) sheet was fabricated through a densification process of low melting PET fiber (LMF) combined PET sheet. During the thermal heat treatment process of the combined LMF, individual PET fiber was connected, which in turn leads to the improvement of the interfacial bonding force between the fibers. Also, the densification of the PET sheet leads to reduce macrospore density and in return could enhance the binding force between the overlapped PET networks. Consequently, the asprepared LMF-PET sheet showed about 410% improved tensile strength and the same elongation compared to before compression. Besides, the enhanced bonding force can prevent the shrinkage of the PET fiber network and exhibited excellent dimensional stability.

• Polymer(Korea)
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• v.31 no.1
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• pp.80-85
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• 2007

Maleic anhydride (MA) modified ethylene-propylene-diene terpolymer (MEPDM) was pre-pared from solution polymerization. MEPDM-g-PST copolymer was prepared by melt polymerization of male ate d EPDM and quaternary ammonium silyl polydimethylsiloxane -7,7,8,8- tetracyanoquinodimethane (TCNQ) adduct (PST) in internal mixer and MEPDM-g-PST/HDPE/CB (MPEC) was prepared by com-pounding HDPE, MEPDM-g-PST copolymer and carbon black (CB, 5, 10, 15, and 20 phr), and HDPE/ CB (PEC) by compounding HDPE and CB (5, 10, 15, and 20 phr), respectively. The structure of MEPDM-g-PST copolymer was confirmed by measuring the FTIR. The maximum grafting ratio of MA onto EPDM was 2.35%. The thermal and mechanical properties of the composites were measured and dispersion characteristics of CB in matrix show that CB in MPEC was better dispersed than that in PEC composite.

• Journal of the Korean Institute of Gas
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• v.18 no.3
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• pp.31-37
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• 2014

The aim of this work is to provide new experimental data on the pyrolysis characteristics and the minimum ignition energy (MIE) by using the same high-density polyethylene (HDPE) powder in domestic HDPE dust explosion accident. To evaluate the explosion sensitivity of HDPE, thermo-gravimetric analysis (TGA), differential scanning calorimeter (DSC) and MIE apparatus (MIKE-3, K$\ddot{u}$hner) was conducted. The measurements showed the volume median diameter of $61.6{\mu}m$ but the particle number density of 98 % in the range $0.4{\sim}4{\mu}m$. The ignition temperature from the results of TGA and DSC in HDPE dust layers was observed in the range of $380{\sim}490^{\circ}C$. MIE was measured under 1 mJ in the HDPE dust concentration of $1200{\sim}1800g/m^3$, it was found that the ratio of particle number density in the range $0.4{\sim}4{\mu}m$ was very high (98%).

• Elastomers and Composites
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• v.36 no.1
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• pp.22-29
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• 2001

For a purpose of recycling of waste tires, composites of 10-60wt% recycled tire crumb blended with high density polyethylene(HDPE) were prepared, and their mechanical properties such as tensile strength, elongation at break, tensile modulus and impact strength were investigated as a function of tire crumb content. Ethylene-acrylic acid(EAA) copolymer was introduced by 10phr as a compatibilizer and the mechanical properties of the composites were measured. For the blend composition of 40wt% tire crumb content showing improved impact strength, the mechanical properties were measured by varying the EAA content of 5-15phr. All blends, whether modified or unmodified, showed a gradual improvement in impact strength as the tire crumb content increased, but the other properties decreased compared with the pure HDPE. In particular, the addition of EAA copolymer to the tire crumb content over 30wt% showed substantial improvement in impact strength. There was no significant effect of tire crumb size on impact strength of the composites.

• Polymer(Korea)
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• v.29 no.4
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• pp.385-391
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• 2005

Reactive melt processing has been carried out to investigate crosslinking characteristics of high density polyethylene OTDPE) with dicummyl peroxide (DCP) and perbutyle peroxide (PBP). The increase of torque in the internal mixer indicated that the crosslinking in HDPE has been occurred by peroxides. As a result, the substantial decrease of density, melting temperature, and melt enthalpy were found while the melt viscosity increased in partially crosslinked HDPE. In the mechanical properties of partially crosslinked HDPE, the increase of maximum strength and the decrease in elongation at break were clearly noticed and these were more pronounced when PBP was applied as a crosslinking agent. It seems that the maximum strength was obtained with reactive processing temperature at $150^{circ}C$, however, the mixing time did not affect to the strength of partially crosslinked HDPE.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1043-1051
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• 2008

In polyolefin processes melt index (MI) is the most important controlled variable indicating product quality. Because of the difficulty in the on-line measurement of MI, a lot of MI estimation and correlation methods have been proposed. In this work a new dynamic MI estimation scheme is developed based on system identification techniques. The empirical MI estimation equation proposed in the present study is derived from the $1^{st}$-order dynamic models. Effectiveness of the present estimation scheme was illustrated by numerical simulations based on plant operation data including grade change operations in high density polyethylene (HDPE) processes. From the comparisons with other estimation methods it was found that the proposed estimation scheme showed better performance in MI predictions. Using the model predictive control method based on the present dynamic MI estimation model, MI values are estimated and compared with those of MI setpoints. From the numerical simulation of the proposed control system, it was found that significant reduction of transition time and the amount of off-spec during grade changes were achieved.

• Clean Technology
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• v.5 no.2
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• pp.45-52
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• 1999

Recycling of red mud from the aluminium manufacturing process was investigated to be utilized as plastic fillers. High density polyethylene(HDPE), low density polyethylene(LDPE) and polypropylene(PP) were found to be the suitable plastic material for which red mud can be used as fillers. With the addition of red mud the plastic showed red brown color. As the ratio of amount of red mud to plastic increased, the tensile strength increased while the Izod impact strength decreased. About five percent of ethylene vinyl alcohol(EVA) was needed as an additive to prevent the lowering of impact strength. Maleic anhydride modified polypropylene was effective for reduction of impact strength lowering of PP. Mixed waste plastics containing LDPE, HDPE, PP, polystyrene and ABS could also accommodate red mud as fillers. In this case, significant loss in mechanical properties were observed due to immiscibility between the components. Ethylene propylene rubber(EPR) and styrene butadiene styrene block copolymer (SBS) could be used to improve the impact properties of the commingled waste plastics.

• Clean Technology
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• v.19 no.4
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• pp.393-400
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• 2013

In this study, Polyethylene wax, which was produced in manufacturing process of high density polyethylene was grafted with maleic anhydride (MAH). The influences of reaction parameters on the graft polymerization as well as the effect of hydrolysis of the anhydride functions were investigated. The results show that the grafting degree increased and conversion of maleic anhydride decreased with an increase in MAH monomer content. This means the highest grafting efficiency for the reaction can be met when MAH monomer content is about 15 wt%. DCP (dicumyl peroxide) and DTBP (di-tert-butyl peroxide) have been used as the initiator and the highest yield of grafting was obtained when the initiator content is about 0.5 wt%. However, It can be seen that the gel content values of this polyethylene wax grafted MAH were below 2%. It was also observed that the grafting degree increased with an increase in reaction temperature and the maximum value was reached 2 hours later. Although MAH functions grafted onto polyethylene wax were mainly in the carboxylic acid forms, some anhydride form of MAH appeared in over 5% of grafting degree. As a result of hydrolysis reaction, it was observed that the conversion of anhydride group into carboxylic acid group was reached up to 10%.

• Bulletin of Food Technology
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• v.9 no.2
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• pp.111-127
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• 1996

Potassium Sorbate의 향균능력측정결과 효모(Saccharomyces cerevisiae)의 성장에 대하여 uncompetitive 기작으로 작용하였다. 열처리 실험의 결과 Potassium Sorbate는 가열온도에 대하여 Arrhenius, 또한 가열시간에 대하여 1차반응식관계로 향균능력을 잃었으며 따라서 보존제로 Potassium Sorbate를 식품에 첨가후 포장, 가열살균하는 일반 식품가공공정상에서 가열살균공정이 첨가 보존제의 잔류향균능력을 잃게 하는 것으로 나타났다. 플라스틱 film과 치즈안에서 Potassium Sorbate의 확산계수 및 확산에 의한 물질전달 현상을 수학적모델과 컴퓨터 simulation 그리고 실험에 의해 구하였다. 저밀도폴리에틸렌(LDPE)이 범용플라스틱중에서 가장 작은 확산계수를 가져 빠른 물질전달이 요구되는 film층 또는 약물저장층으로 적합한것으로 나타났다. 그외 고밀도 폴리에틸렌(HDPE)과 폴리프로필렌(PP), 폴리에스터(PET)는 느린 물질전달이 요구되는층 또는 복합다층 film에서 물질전달에 단방향성을 주는 고차단층으로 적합한것으로 나타났다. Potassium Sorbate분말과 LDPE resin분말을 섞은후 단일스크루 익스트루더로 항균성 포장 film을 제조한 결과 LDPE film의 tensile strength과 elongation, elastic modulus는 Potassium Sorbate를 3% 이상 포함할때까지 변화하지 않았다. 그러나 film의 투명도는 급격히 낮아졌다. 향균성LDPE film은 효모가 접종된 한천배지상에서 항균물질인 Potassium Sorbate를 배지위로 서서히 방출시켜 효모의 성장속도(growth rate)를 저하시키고 초기성장지체기(lag period)를 연장시킨다. 따라서 식품포장재로 적용시에 미생물의 오염을 막고 식품저장기간을 연장할것이라 여겨진다.

• Resources Recycling
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• v.13 no.5
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• pp.23-27
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• 2004

In this study, experimental work was performed to mold tensile specimens by using the injection molding machine. Melt temperature, mold temperature and the mixed ratio of recycled resin were selected as processing parameters for studying the effect of those conditions on the shrinkage, weight, absorption, and tensile strength of molded parts. As a result, the shrinkage was increased according to the higher mold and melt temperature and it was more sensitive to the change of mold temperature. On the other hand, the weight of molded parts was decreased due to the increment of mold and melt temperature. Tensile strength was increased with mold and melt temperature, and it was also easy to change by mold temperature.