• Elastomers and Composites
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• v.56 no.4
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• pp.201-208
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• 2021

In this study, the effect of petroleum resin on the mechanical strength, morphology, and vibration damping characteristics of natural rubber (NR) composites was observed. The NR composites plasticized by adding petroleum resin showed decreased hardness and mechanical properties. A morphology analysis indicated that as the amount of petroleum resin increased, carbon black aggregates (or agglomerates) observed at the fracture surface decreased, resulting in an improvement in the dispersibility. In addition, as 20 phr of petroleum resin was added, the effective damping temperature range increased by approximately 11.4%, the hysteresis loss rate increased by 15.2%, and the resilience decreased by 36.6%. Therefore, it was confirmed that the vibration damping characteristics improved with the addition of petroleum resin. This was because the rubber-filler interaction between the NR molecular chain of the NR composite and the carbon black particles improved by the addition of petroleum resin.

• Journal of the Semiconductor & Display Technology
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• v.18 no.2
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• pp.11-16
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• 2019

The four different polymer compounds were manufactured with the two kinds of plasticizers [(di-2-ethylhexyl sebacate(DOS), and di-2-butyl sebacate(DBS)] and two different additive amounts(18, 26 phr) of the same plasticizer for making cable sheath for ship. Ethylene-vinylacetate, ethylene-propylene-diene-copolymer as matrix polymers and ethylene-vinylacetate grafted maleic anhydride as coupling agent were selected for compounding with fire retardant, closslinking agent, filler, and other additives besides plasticizer. The compound including DOS showed the higher ${\Delta}T$ than that including DBS at the same additive amount in the rheology test. And with increasing plasticizer, the compounds resulted in lower tensile strength and higher elongation by lubricating effect of plasticizer. DOS yielded better aging resistance and cold resistance than DBS due to the good heat resistance and low solidifying point of DOS compared to DBS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.1
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• pp.302-322
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• 2021

In the system of ciphertext policy attribute-based encryption (CP-ABE), only when the attributes of data user meets the access structure established by the encrypter, the data user can perform decryption operation. So CP-ABE has been widely used in personal health record system (PHR). However, the problem of key abuse consists in the CP-ABE system. The semi-trusted authority or the authorized user to access the system may disclose the key because of personal interests, resulting in illegal users accessing the system. Consequently, aiming at two kinds of existing key abuse problems: (1) semi-trusted authority redistributes keys to unauthorized users, (2) authorized users disclose keys to unauthorized users, we put forward a CP-ABE scheme that has authority accountability, user traceability and supports arbitrary monotonous access structures. Specifically, we employ an auditor to make a fair ruling on the malicious behavior of users. Besides, to solve the problem of user leaving from the system, we use an indirect revocation method based on trust tree to implement user revocation. Compared with other existing schemes, we found that our solution achieved user revocation at an acceptable time cost. In addition, our scheme is proved to be fully secure in the standard model.

• Elastomers and Composites
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• v.56 no.1
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• pp.6-11
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• 2021

In order to develop an ultra-high-density elastomeric material for substitution of steel dynamic dampers, a new curing system and technique for high-loading of the filler were examined in this study. Mechanochemical modification of chloroprene rubber (MAH-g-CR) using an internal mixer was carried out with maleic anhydride (MAH) as a reactive monomer. The optimum amount of MAH was 10 phr and the efficient grafting of MAH on CR could be achieved at a mixing temperature of 100℃. After preparing MAH-g-CR, 50 mol% epoxidized natural rubber (ENR 50) was blended with MAH-g-CR to develop a "self-curable rubber blend system" via reaction between the functional groups of the elastomeric matrices without the curing agent and additives. The content of ENR 50 was fixed at 30 wt.% throughout evaluation of the curing behavior of the MAH-g-CR/ENR blend. Tungsten powder was added to the MAH-g-CR/ENR matrix up to 60 vol.% to obtain ultra-high-density, and the maximum density obtained was 7.57 g/㎤. Stable ts2 (scorch time) and t90 (90% cure time) could be obtained even when tungsten powder was incorporated up to 60 vol.%. In addition, the tensile strength and damping properties of MAH-g-CR/ENR containing 60 vol.% of tungsten were better than those of CR containing 60 vol.% of tungsten.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4977-4983
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• 2015

The full depth excavation induces couple of technical and social problems like increase of construction cost and time for excavation and backfill, increase of public complains and delay of traffic, and so force. In order to overcome these problems, lots of laboratory tests were carried out for sewer pipeline of maintenance materials with trenchless methods. The testing materials are PVC strip and then the lab tests were followed by Korean Standard. We will treat the structure safety and pipe integrity of PVC profile more excellent than the profile have application to SPR. There is no side-effect to process and to satisfy the criteria of tensile strength, impact strength and softening temperature. The profile with resin adhesive showed no leakage of water at specific pressure.

• Journal of the Korean Wood Science and Technology
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• v.45 no.3
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• pp.288-296
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• 2017

In this study, the effect of spray-drying conditions and surfactant addition on the spray-drying yield, morphological characterization, size distribution and re-dispersity in water of spray-dried lignocellulose nanofibril (LCNF) were investigated. The freeze-dried LCNF after solvent exchange had linear fiber morphology with a diameter of 70-300 nm, and the spray-dried LCNF showed rod-like particle morphology. The spray-drying yield and particle size of spary-dried LCNF at $140^{\circ}C$ was highest and smallest, respectively. As LCNF concentration and blowing rate decreased and increased, respectively, the spray-drying yield and particle size were increased. The highest spray-drying yield was found at distearyl dimethyl ammonium chloride (DDAC) addition of 10 phr at $140^{\circ}C$. As the particle size decreased and the DDAC content increased, filtration time of spray-dried LCNF in water was decreased and increased, respectively.

• Textile Coloration and Finishing
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• v.30 no.2
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• pp.107-116
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• 2018

Simplification of the manufacturing process in shoe making is essential to improve productivity and reduce production costs. To improve the adhesion of EVA foam used as a midsole, EVA/itaconated EPDM(EPDM-g-IA)(80/20wt%) blend was prepared using Torque Rheometer-Plasti-Corder, and 1,6-hexamethylenediamine/crosslinking agent/foaming agent/additive were mixed, followed by amidation reaction and foaming to prepare EVA/EPDM-g-IA foam for shoe midsole. In this study, we investigate the effect of the content of 1,6-hexamethylenediamine(0, 0.5, 1.0, 2.0, 3.0) on the mechanical properties, water-contact angle and adhesion of EVA/itaconated EPDM foam. As the content of 1,6-hexamethylenediamine increased, mechanical properties such as tensile strength, tear strength, tensile elastic modulus, hardness, and water-contact angle were lowered, but elongation at break and compression set(%) were increased. Both normal type and non-UV type adhesive strength increased with increasing diamine content. In particular, it was found that the adhesion strength of the non-UV type adhesion increased sharply with increasing diamine content. As a result, an adherend rupture occurs in a foam sample having a content of 1,6-hexamethylenediamine of 3phr. From this, it can be seen that the EVA/itaconated EPDM foam for shoe midsoles, which can be used for non-UV adhesion without primer and UV treatments, have been developed.

• Korean Management Science Review
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• v.13 no.2
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• pp.25-48
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• 1996

Mixed Model Assembly Lines (MMALs) are increasingly used to produce differentiated products on a single assembly line without work-in-process storage, Usually, a typical MMAL consists of a number of (1) stations doing exactly the same operation on every job, (2) stations involving operations with different choices, and (3) stations offering operations that are not performed on every job, or that are performed on every job but with many options. For stations of the first type there is no sequencing problem at all. However, for the second type a set-up cost is incurred each time the operation switches from one choice to another. At the third type of stations, different models, requring different amounts and choices of assembly work, creates an uneven flow of work along the line and variations in the work load at these stations. When a subsequence of jobs requires more work load than the station can handle, it is necessary to help the operations at the station or to complete the work elsewhere. Therefore, a schedule which minimize the sum of set-up cost and utility work cost is desired. So this study has developed Fixed Random Ordering Rule (FROR), Fixed Ascending Ordering Rule (FAOR), Fixed Descending Ordering Rule, and Extended NHR (ENHR). ENHR is to choose optimal color ordering of each batch with NHR, and to decide job sequence of the batch with it, too. As the result of experiments, ENHR was the best heuristic algorithm. NHR is a new heuristic rule in which only the minimum addition of violations from both partial sequence and unassigned sequence at every branch could be considered. And this is a heuristic sequencing rule for the third type of stations at MMAL. This study developed one more heuristic algorithm to test the performance of NHR, which is named as Practical Heuristic Rule (PHR).

• Journal of the Korean Wood Science and Technology
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• v.42 no.4
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• pp.483-490
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• 2014

The effect of microfibrillated cellulose (MFC) content and coupling agent (polymeric methylene diphenyl diisocyanate, pMDI) on the properties of MFC-reinforced polybutylene succinate (PBS) nanocomposite. With increasing MFC content, tensile strength and elastic modulus were increased. More than 1.5 times in tensile strength of PBS/MFC(70/30) nanocomposite was improved by the addition of pMDI (1 phr), compared to the nanocomposite without pMDI. This trend was being significant in nanocomposite with higher MFC content. Thermal stability of the nanocomposite was increased by the addition of pMDI. These improvements is considered to be due to the improvement of MFC dispersion and interfacial adhesion between MFC and PBS matrix.

• Composites Research
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• v.27 no.1
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• pp.25-30
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• 2014

The actuation performance of an EADE (Electro-active dielectric elastomer) is studied as functions of thinner content, thickness and types of the dielectric elastomer such as natural (NR), acrylonitrile-butadiene (NBR), and silicon (KE-12) rubbers. With a decrease in elastomer thickness ($1{\rightarrow}0.5{\rightarrow}0.25{\rightarrow}0.1{\rightarrow}0.05$ mm) and an increase in thinner content ($0{\rightarrow}30{\rightarrow}50$ phr), the actuating displacement of KE-12 elastomer is increased, however their breakdown occurs at low voltage. For the same thickness (1 mm), the displacement of KE-12 elastomer shows a higher value (2.24 mm) compared to that of NR or NBR at the same applied voltage of 25 kV. The KE-12 has the lowest elastic modulus and the NBR has the highest one among the tested elastomers. However, the displacement of NBR elastomer is higher compared to that of NR because of high dielectric constant. It is found that the important factors of EADE actuator are a thickness, modulus and dielectric constant of the elastomer.