• Elastomers and Composites
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• 제58권3호
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• pp.128-135
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• 2023

To improve the adhesive strength of natural rubber (NR) for a seismic isolation damper, citraconic acid-g-NR (CCA-g-NR) was synthesized via the melt grafting of citraconic acid (CCA) onto NR using an azobisisnomerobutyronitrile (AIBN) initiator. Subsequently, the influence of CCA and AIBN concentrations on the graft ratio G/R (%) and graft efficiency G/E (%) of the CCA-g-NR was investigated. The optimum CCA and AIBN concentrations required to achieve the desired G/R (3.49%) and G/E (49.8%) were found to be 7 phr and 0.13 phr, respectively. Additionally, we studied the influence of CCA-g-NR concentration on the mechanical properties (tensile strength, elongation at break, and modulus at 300%), adhesive strength, and cure characteristics of the rubber compound in the seismic isolation damper. As the concentration of CCA-g-NR increased, the elongation at break and adhesive strength of the compound increased, whereas its tensile strength and modulus at 300% decreased. Moreover, as the concentration increased, the maximum torque decreased and the scorch time was delayed to obtain an optimal vulcanization time.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 The Korea-Japan Joint Symposium
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• pp.98-98
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• 2003

Mechanical Properties of NR/PET fiber composite were studied. First, PET fiber was grafted under EB irradiation. The mechanical properties of composite were improved with the addition of grafted fiber into NR.

• Elastomers and Composites
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• 제51권4호
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• pp.342-349
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• 2016

Characteristics of the swelling-induced wrinkles on the surfaces of natural rubber (NR) film were investigated. The wrinkle structure was generated by swelling of NR film pre-stretched and firmly bonded onto an aluminum substrate in hexane. A novel experimental method was adopted to replicate the swelling-induced wrinkles on the NR film using an epoxy-hardener system. To get insight into the wrinkle parameters; the wrinkle length (L), wrinkle distance (D), wrinkle height (H) and the angle between two consecutive wrinkles (${\theta}$), the cross-sections of the replicas obtained from saturated swollen NR film were examined using an optical microscopy (OM). From the OM images, the wrinkling parameters were measured as a function of the thickness of NR film from 0.42 to 1.76 mm. Also, it was evaluated that the effects of swelling time on the wrinkling parameters. The length (L), distance (D) and height (H) of wrinkles increased as the thickness of the NR film and the swelling time increased. However, the angle between the wrinkles (${\theta}$) showed a sharp decrease up to a swelling time of 200 minutes and slightly decreased afterwards.

• Environmental Engineering Research
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• 제20권4호
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• pp.342-346
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• 2015

Haloacetonitriles (HANs) are nitrogenous disinfection by-products (DBPs) that have been reported to have a higher toxicity than the other groups of DBPs. The adsorption process is mostly used to remove HANs in aqueous solutions. Functionalized composite materials tend to be effective adsorbents due to their hydrophobicity and specific adsorptive mechanism. In this study, the removal of dichloroacetonitrile (DCAN) from tap water by adsorption on thiol-functionalized mesoporous composites made from natural rubber (NR) and hexagonal mesoporous silica (HMS-SH) was investigated. Fourier-transform infrared spectroscopy (FTIR) results revealed that the thiol group of NR/HMS was covered with NR molecules. X-ray diffraction (XRD) analysis indicated an expansion of the hexagonal unit cell. Adsorption kinetic and isotherm models were used to determine the adsorption mechanisms and the experiments revealed that NR/HMS-SH had a higher DCAN adsorption capacity than powered activated carbon (PAC). NR/HMS-SH adsorption reached equilibrium after 12 hours and its adsorption kinetics fit well with a pseudo-second-order model. A linear model was found to fit well with the DCAN adsorption isotherm at a low concentration level.

• Elastomers and Composites
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• 제29권2호
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• pp.121-130
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• 1994

The physical properties of rubber blend between natural rubber(NR) and ethylene propylene diene terpolymer(EPDM) were investigated as a study of EPDM composite materials. For EPDM/NR blends, the effects of ethylene and diene contents in EPDM, blend ratio, dicumyl peroxide(DCP) curing system on the physical properties, interfacial adhesion force and dynamic crack growth etc. were studied. EPDM/NR blends loaded with carbon black were prepared by mechanical mixing and cured by plate heating cure press. Crosslinking density was measured by swelling method with toluene. The physical properties of all blends were measured with Instron, fatigue to failure(FTF), Demattia flex cracking tester(DMFC), scanning electron microscopy (SEM), etc. As the ethylene and diene contents in EPDM increased, the physical properties, such as dynamic crack growth, adhesion to other component were increased too. Interfacial adhesion force of EPDM/NR blends to dissimilar layer was improved by the use of optimum peroxide curing system.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1565-1570
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• 2020

Photons with the energy of 60 keV are regularly used for some kinds of bone density examination devices, like the single photon absorptiometry (SPA). This article reports a flexible and lightweight rare earth/polymer composite for enhancing shielding efficiency against photon radiation with the energy of 60 keV. Lead oxide (PbO) and several rare earth element oxides (La₂O₃, Ce₂O₃, Nd₂O₃) were dispersed into natural rubber (NR) and the photon radiation shielding performance of the composites were assessed using monte carlo simulation method. For 60 keV photons, the shielding efficiency of rare earthbased composites were found to be much higher than that of the traditional lead-based composite, which has bad absorbing ability for photons with energies between 40 keV and 88 keV. In comparison with the lead oxide based composite, Nd₂O₃-NR composite with the same protection standard (the lead equivalent is 0.25 mmPb, 0.35 mmPb and 0.5 mmPb, respectively), can reduce the thickness by 35.29%, 37.5% and 38.24%, and reduce the weight by 38.91%, 40.99% and 41.69%, respectively. Thus, a flexible, lightweight and lead-free rare earth/NR composite could be designed, offering efficient photon radiation protection for the users of the single photon absorptiometry (SPA) with certain energy of 60 keV.

• Macromolecular Research
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• 제15권5호
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• pp.482-485
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• 2007

• Elastomers and Composites
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• 제56권4호
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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.

• Composites Research
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• 제27권1호
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• pp.25-30
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• 2014

실리콘 KE-12, NBR 그리고 NR 등의 유전 탄성체 종류, 두께 및 희석제 함유량을 함수로 한 전기활성 유전탄성체(EADE) 구동 성능에 대해 연구하였다. 탄성체의 두께($1{\rightarrow}0.5{\rightarrow}0.25{\rightarrow}0.1{\rightarrow}0.05$ mm)의 감소에 따라 그리고 희석제의 함유량 증가에 따라 KE-12 탄성체의 작동변위는 증가하였지만, 유전파괴는 낮은 전압에서 발생되었다. 동일한 탄성체 두께(1 mm)에 대해서 KE-12의 변위(2.24 mm)는 동일한 전압(25 kV)에서 NBR 혹은 NR보다 더 높게 나타났다. 시험한 탄성체 종류 중 KE-12는 가장 낮은 탄성계수를 NBR은 가장 높은 탄성계수 나타냈다. 하지만, NBR 탄성체의 변위는 높은 유전상수 때문에 NR의 경우 보다 높았다. EADE 구동기의 중요한 요소는 탄성체의 두께, 탄성계수 및 유전상수임을 확인하였다.

• Elastomers and Composites
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• 제46권3호
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• pp.237-244
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• 2011

비보강, 카본블랙, 카본블랙과 실란커플링제, 실리카, 실리카와 실란커플링제 등 5가지의 다른 충전 시스템을 갖는 NR 복합체를 열노화시켰으며, 가속 열노화에 의한 가교밀도 변화를 연구하였다. 가교밀도는 충전 시스템과 관계없이 노화 시간이 경과함에 따라 증가하였다. 노화 온도가 높아질수록 가교밀도는 눈에 띄게 변하였다. 카본블랙으 로 보강된 NR 복합체의 경우, 실란커플링제는 가교밀도를 증가시켰다. 하지만 실리카로 보강된 NR 복합체의 경우에는 $60^{\circ}C$와 $70^{\circ}C$ 노화에서는 가교밀도 증가분이 감소하였으며, $80^{\circ}C$와 $90^{\circ}C$에서는 거의 영향을 주지 않았다. 카본블랙으로 보강된 NR 복합체의 가교밀도 변화에 대한 활성화 에너지는 로그 함수 형태로 지속적으로 증가한 반면, 실리카로 보강된 NR 복합체의 경우에는 노화 시간 30-150일 구간에서는 거의 변화가 없었다. 비보강 시험편의 활성화 에너지 는 노화 시간에 따라 지수 함수 형태로 증가하였다. 실험 결과는 실란커플링제로부터의 황 제공, 실란커플링제에 의한 충전제의 표면 개질, 실리카 표면에서의 가교제 잔류물의 흡착, 그리고 흡착된 가교제 잔류물의 방출 등으로 설명하였다.