• Elastomers and Composites
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• v.58 no.3
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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.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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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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• v.51 no.4
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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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• v.20 no.4
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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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• v.29 no.2
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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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• v.52 no.7
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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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• v.15 no.5
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• pp.482-485
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• 2007

• 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.

• 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.

• Elastomers and Composites
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• v.46 no.3
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• pp.237-244
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• 2011

Five natural rubber (NR) composites with different reinforcing systems of unfilled, carbon black, carbon black with silane coupling agent, silica, and silica with silane coupling agent were thermally aged and change of the crosslink densities by the accelerated thermal aging was investigated. The crosslink densities on the whole increased as the aging time elapsed irrespective of the reinforcing systems. The crosslink density changes became noticeable by increasing the aging temperature. For carbon black-filled composites, the silane coupling agent made the crosslink density change to be increased. For silica-filled composites, however, the silane coupling agent made the crosslink density increment reduced at 60 and $70^{\circ}C$ and it hardly affect the degree of the crosslink density change at 80 and $90^{\circ}C$. The activation energies for the crosslink density changes of the carbon black-filled samples increased continuously in a logarithmic fashion, whereas that of the silica-filled one showed a quasi-steady state ranges at aging times of 30-150 days. The activation energy of the unfilled sample increased exponentially with the aging time. The experimental results were explained with sulfur donation from the silane coupling agent, surface modification of the filler by the silane coupling agent, adsorption of curative residues on the silica surface, and release of the adsorbed curative residues.