• Title, Summary, Keyword: natural rubber

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Composition-Dependent Properties of Natural Rubber Blended with Butadiene Rubber (배합비에 의한 고무 블렌드의 물성변화)

  • Kwon, Kih-Wan;Park, Moon-Soo
    • Elastomers and Composites
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    • v.31 no.5
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    • pp.347-352
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    • 1996
  • A natural rubber was blended with a butadiene rubber with different ratios. A natural rubber, along with three different blends, its ratio varying from 10 to 15 to 20 weight %, were prepared and tested. It was found that inclusion of the butadiene rubber increased cure time, compared to the natural rubber. It is speculated that increased free volume due to the inclusion of butadiene rubber contributed to this effect. Furthermore, inclusion of butadiene rubber led to increase hardness of a sphere, and as a result, the extent of rebound increased sharply.

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Effect of Kenaf Fiber Loading on the Properties of Natural Fiber/Natural Rubber Composites (천연섬유/천연고무 복합재료의 특성에 미치는 Kenaf 섬유함량의 영향)

  • Cho, Yi-Seok;Cho, Dong-Hwan
    • Elastomers and Composites
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    • v.46 no.3
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    • pp.186-194
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    • 2011
  • Natural fiber/natural rubber composites were fabricated by uniformly compounding natural rubber and cellulose- based natural fiber kenaf and then by compression molding. The effect of kenaf fiber content on their vulcanization behavior, hardness, tensile properties, tear strength and static and dynamic properties was investigated. The contents of kenaf fiber in the composites were 0, 5, 10, 15, and 20 phr, compared to natural rubber and additives. The result indicated that various properties of natural rubber depended on the kenaf fiber content. With increasing kenaf fiber content, the torque for vulcanization of natural rubber was increased whereas the vulcanization time was reduced as well. The hardness, tensile modulus and tear strength of kenaf/natural rubber composites were gradually decreased with the fiber content whereas the tensile strength and elongation at break were decreased. Also, with increasing the kenaf fiber content the dynamic property of natural rubber was changed more greatly than the static property. The loss factor, which is closely related with the damping or absorption of the energy given to natural rubber, was proportionally increased with the fiber content.

A study on the change of physical properties of elastomer in high temperature curing (고온가황에 의한 탄성체의 물성변화에 관한 연구)

  • Lee, Jeung-Ho
    • Elastomers and Composites
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    • v.19 no.3
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    • pp.163-177
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    • 1984
  • The effect of curing temperature increase and sulfur amount added were studied with natural and synthetic rubbers. Also, the effects of TMTD, MBTS and mixture of zinc soaps of high molecular fatty acids added to natural rubber were investigated respectively. The experimental results showed that, in the case of the conventional curing ($145^{\circ}C$), natural rubber, compared with synthetic rubber, gave higher values in elongation, tensile strength, cure rate, and lower values in modulus change. But, at high temperature curing ($180^{\circ}C$), natural rubber showed faster reversion rate, and higher heat build-up compared to synthetic rubber, than in the conventional curing. Also, natural rubber produced at high temperature showed severe degradation in hardness and tensile strength before heat-aging as well as in hardness, modulus and tensile strength after heat-aging. Improved reversion effect was obtained with natural rubber either by blending mixture of zinc soaps of high molecular acids or by applying semi-efficient vulcanization system.

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Recycling Natural Rubber Vulcanizates through Mechanochemical Devulcanization

  • Jang G. K.;Das C. K.
    • Macromolecular Research
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    • v.13 no.1
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    • pp.30-38
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    • 2005
  • Sulfur-cured gum natural rubber vulcanizates were devulcanized using two different concentrations of diallyl disulfide. The devulcanization process was performed at $110^{\circ}C$ min in an open two-roll cracker-cum-mixing mill. Natural rubber vulcanizates having various sulfur/accelerator ratios were used to study the cleavage of monosulfide, disulfide, and polysulfide bonds. The properties of devulcanized natural rubber increased upon increasing the disulfide concentration and the mechanical properties of the revulcanized natural rubber increased upon decreasing the sulfur content in the original rubber vulcanizates. The scorch time and the maximum state of cure both increased when the ground vulcanizates were treated with higher amounts of disulfide. TGA and DMA were conducted to study the effects of the devulcanization on the thermal stability and the $T_g$ behavior of the vulcanizates. SEM analysis was conducted to study how the failure mechanism was affected by the devulcanization process. It was possible to recover $70-80\%$ of the original gum rubber properties by using this process. From IR spectroscopic analysis, we observed that the oxidation of the main chains did not occur during high-temperature milling.

Influence of the Vulcanization on the Dielectric Proper ties of the Ageing Natural Nubber (노화된 천연고무의 유전특성에 미치는 가황의 영향)

  • Kim, Bong-Heup;Kim, Wang-Kon;Lee, Joon-Ung
    • Elastomers and Composites
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    • v.21 no.3
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    • pp.205-212
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    • 1986
  • The dielectric properties of natural rubber are very important to investigate the molecular structure. The charcteristics of the dielectric absorption in aging natural rubber were studied in the range of frequency from $1{\times}10^3Hz\;to\;3.2{\times}10^7Hz$ at the temperature of $23^{\circ}C$. As the results, it has been confirmed that in the case of aged NR vulcanized specimen with contained sulfur 2 phr above the specimens exhibit two kind of dielectic losses due to the the dipole polarization by impurities and sulfurs, and of raw rubber exhibit the kind of losses due the to dipole polarization. Particularly, it has been affirmed that the dielectric loss spectrum of the aging natural rubber is larger than that the natural rubber, and the dielectric strength of the aging natural rubber drop depreciate respctively.

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Effects of Reactive Compatibilizers on the Morphology and Properties of Natural Rubber/SiO2 Composites

  • Lee, Min Young;Park, Jin Young;Song, Ki Chan;Kim, Su Kyung
    • Elastomers and Composites
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    • v.51 no.2
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    • pp.106-112
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    • 2016
  • Maleimidopropyltriethoxysilane grafted natural rubber (MISNR) was prepared by reaction of maleic anhydride grafted natural rubber and 3-aminopropyl triethoxysilane. MISNR was used as the compatibilizer of natural rubber/silica composites. The composites were prepared by two-step mixing procedures. The final mixtures were cured with optimum cure condition, which was established by a rheometer. Effects of the amounts of compatibilizer in the composites on the cure characteristics, morphology, thermal stability, and physical and mechanical behaviors were investigated. The composites having MISNR had shown cure characteristics and physical and mechanical properties superior to those without MISNR. Silica particles in the former appeared to be more uniform and reduced in size compared with the latter. The effects of the types of silica were also evaluated.

Study in the Mechanisms of Formation of Transfer Film under the Condition of Wear of Steel AISI1020 by Natural Rubber

  • Wang, De-Guo;Zhang, Si-Wei;He, Ren-Yang;Li, Ming-Yuan
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.223-224
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    • 2002
  • The mechanisms of formation of transfer film under the condition of wear of Steel AISI1020 by natural rubber were investigated. The transfer film was observed and the formation mechanisms were clarified. The formation process of transfer film on the worn surface of the steel could be divided into two stages. Firstly, the adhesive layer emerged on the worn surface of the steel by adhesion of natural rubber. in which the macromolecular chains of natural rubber joined to the surface of the steel by Van der Waals' force. And then, the iron atom and metal oxide reacted with the macromolecular of natural rubber in the adhesive layer and produced Fe-polymer compound. As a result, the transfer film was formed on the worn surface of the steel. The transfer film was joined to the worn surface of the steel by the chemical bonds and electrostatic force.

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The Effect of Viscosity of Natural Rubber on Incorporation Rate of Carbon Black in The Mixing (배합중 카본블랙 혼입속도에 천연고무 점도가 미치는 영향)

  • Kang, Yong-Gu;Han, Shin;Lee, Kye-Jung;Ryu, Dong-Wan;Park, Chan-Young
    • Journal of the Korean Society of Industry Convergence
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    • v.2 no.1
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    • pp.97-103
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    • 1999
  • The power curve during rubber mixing presents useful information for the understanding of rubber mixing process, because the power curve is determined the mixing state of rubber at the point. The time to the second peak on the power curve is known as carbon black incorporation time, BIT. This study gets the quantity relationship of BIT and viscosity of natural rubber, so by determining the mixing time of the compound on the ground of viscosity of the raw rubber. The mixing with natural rubber and carbon black is examined for various grade natural rubbers, encompassing a wide range of Mooney viscosity. Alter smoothing the mixing power curve using a polynomial, the carbon black incorporation time, BIT, was determined time to second power peak on the curve, The BIT's versus specific values on Mooney viscometer test curve show a linear relation, Especially, the peak of initial maximum torque on Mooney viscometer curve, PMT, is most relevant property relating to the BIT. PMT is useful index for determined optimum mixing time, To apply this results at the mixing, we effectively control the natural rubber mixing but can also know the grading of natural rubber upon processability.

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Effects of Maximum Strain and Aging Conditions on the Fatigue Life of Vulcanized Natural Rubber (가황 천연고무의 피로수명에 미치는 최대 변형률과 노화도 영향)

  • 우창수;김완두;김완수;권재도
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.4
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    • pp.181-190
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    • 2004
  • The interest of the fatigue life of rubber components such as engine mounts is increasing according to the extension of warranty period of the automotive components. Automotive engine mounts get damaged due to thermal and mechanical loadings. This paper discusses a fatigue life prediction of the 3-dimensional dumbbell specimens for natural rubber compound considering the effects of maximum strain and heat aging temperature. Displacement controlled fatigue life tests were performed using specimens with different levels of maximum strain and various hardness. The basic mechanical properties test and the fatigue test of aged rubber specimen under normal and elevated temperature were executed. A procedure to predicted the fatigue life of vulcanized natural rubber material based on the maximum strain method was proposed, and then this curve was in good agreement with fatigue test data less than 200% error range.

A Study on Recycling of EPDM Reclaimed Rubber (폐 EPDM 고무의 재활용을 위한 기초적 연구)

  • Jang, Doo-Hee;Kim, Ji-Hoon;Kim, Young-Ju
    • Journal of Environmental Science International
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    • v.19 no.3
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    • pp.365-370
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    • 2010
  • In this study, we carried out the evaluation of EPDM(Ethylene Propylene Diene Monomer) reclaimed rubber mixing with natural rubber at various mixing ratio to reuse as rubber filler. The scorch time and moony viscosity was analyzed to evaluate the effect of cure behavior. And also, we analyzed the tensile strength, the elongation at break and cure time to evaluate the variation of cure behavior. As the results, the scorch time and optimal cure time was decreased according to the increasing of EPDM reclaimed rubber. However, the moony viscosity was increased at each mixing ratio. In case of the added EPDM reclaimed rubber was 20 phr(parts by weight per 100 parts by weight of rubber), the hardness and specific gravity was increased a little. The hardness and specific gravity was increased in rapidly under 40 phr of the added EPEM reclaimed rubber. The tensile strength and elongation at break of the compound of natural and EPDM reclaimed rubber was rapidly decreased compared with its natural rubber when the ratio of adding EPDM reclaimed rubber was over 40 phr.