• Elastomers and Composites
• /
• v.55 no.1
• /
• pp.20-25
• /
• 2020

The effect of the isocyanate index (NCO index) on the particle size and particle size distribution of a waterborne polyurethane dispersion (WPUD) with polycarbonate-diol was determined. The WPUDs were prepared using a conventional acetone process with polycarbonate-polyol (M_n = 2028), 4,4'-methylenebis(cyclohexyl isocyanate) (H₁₂MDI), 2,2-bis(hydroxymethyl) propionic acid (DMPA), and dibutyltin dilaurate catalyst. At NCO index values below 1.5, the number average particle diameter of the WPUDs significantly increased with the NCO index, whereas the particle diameter slightly varied at higher NCO indexes. The dependency of the WPUD viscosity on the NCO index exhibited similar behavior to that of the particle size. The relative values of the full width at half maximum of the WPUD particle distribution curves at various NCO indexes were not influenced by the NCO index.

• Elastomers and Composites
• /
• v.48 no.1
• /
• pp.76-84
• /
• 2013

The term 'Piezoresistive effect' describes a change in the electrical resistance of the material from deformed to its original shape by the external pressure, e.g., elongation, compression, etc. This phenomenon has various applications of sensors for monitoring pressure, vibration, and acceleration. Although there are many materials which have the piezoresistive effect, rubber (nano)composites with conductive fillers have attracted a great deal of attention because the piezoresistive effect appears at the various range of pressure by controlling the type of filler, particle size, particle shape, aspect ratio of particles, and filler content. Especially one can obtain the composites with elasticity and flexibility by using the rubber as a matrix. This paper aims to review the piezoresistive effect itself, their basic principles, and the various conductive rubber-composites with piezoresistive effect.

• Korean Journal of Materials Research
• /
• v.20 no.2
• /
• pp.104-110
• /
• 2010

The characteristics of all polymer composites containing carbon materials are determined by four factors: component properties, composition, structure and interfacial interactions. The most important filler characteristics are particle size, size distribution, specific surface area and particle shape. As a consequence, in this paper we discuss the aspects of the mechanical, electrical and thermal properties of composites with different fillers of carbon black, carbon nanotube (CNT), graphene and graphite and focus on the relationship between factors and properties, as mentioned above. Accordingly, we fabricate rubber composites that contain various carbon materials in carbon black-based and silica based-SBR matrixes with dual phase fillers and use scanning electron microscopy, Raman spectroscopy, a rhometer, an Instron tensile machine, and a thermal conductivity analyzer to evaluate composites' mechanical, fatigue, thermal, and electronic properties. In mechanical properties, hardness and 300%-modulus of graphene-composite are sharply increased in all cases due to the larger specific surface. Also, it has been found that the thermal conductivity of the CNT-composite is higher than that of any of the other composites and that the composite with graphene has the best electrical properties.

• Elastomers and Composites
• /
• v.54 no.4
• /
• pp.335-344
• /
• 2019

In this work, styrene butadiene rubber (SBR) and styrene butadiene styrene (SBS) were used to modify asphalt, resulting in SBR- and SBS-modified asphalt, respectively. The two modified asphalts were emulsified with a nonionic emulsifier (Span 60) and cationic emulsifiers (ID, DDA) and their phase stabilization was investigated via particle size, Zeta potential, and flow behavior analysis. With increasing amount of the mixed emulsifier, the particle size decreased, leading to an increase in viscosity. The shear thinning behaviors and Zeta potential values ranging from 35-65 mV were determined and remained considerably stable. In addition, the adhesion strength and compression strength of the SBR-and SBS-modified asphalt emulsion were evaluated via surface free energy examination. The remarkable adhesion and compression strengths were estimated when 5 phr ID and 6 phr DDA were added to the emulsified asphalt modified with SBR and SBS. Therefore ID and DDA, the two cationic surfactants, played significant roles in improving the dispersion and interfacial adhesion strength, resulting in the improved adhesion and compression strength of the emulsified asphalts modified with SBR and SBS.

• Elastomers and Composites
• /
• v.58 no.3
• /
• pp.103-111
• /
• 2023

The abrasion resistances of silica-filled styrene-butadiene rubber (SBR) compounds prepared with and without dicyclopentadiene resin (SBR-R and SBR-0, respectively) were studied using four different abrasion testers, namely cut and chip (CC), Lambourn, DIN, and laboratory abrasion tester (LAT100). The effect of the resin on the abrasion behavior was elucidated by analyzing the morphologies and size distributions of wear particles. All the wear particles had rough surfaces, but those obtained in the Lambourn abrasion test exhibited relatively smooth surfaces. The size distributions of the wear particles showed different trends depending on the abrasion tester and the rubber compound; however, most of the wear particles were larger than 1000 ㎛. The SBR-R sample showed a wide range of particle sizes (from 63 ㎛) in the LAT100 abrasion test and majority of the wear particles were 500-1000 ㎛, whereas the SBR-0 sample had the most distribution of larger than 1000 ㎛. The abrasion rates of SBR-0 sample were lower than those of the SBR-R sample for the CC and LAT100 abrasion tests, but the Lambourn abrasion test result showed the opposite trend. Addition of the resin influenced the abrasion behavior, however the effect varied depending on the type of abrasion tests.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.11a
• /
• pp.206-209
• /
• 2002

The purpose of this research was to find influence of compounding materials on electrical properties of silicone rubber such as tracking characteristic. The tracking characteristic was tested through controlling the ATH, a widely use anti-tracking agent. Regarding the particle size and coupling agent of ATH, compound silicone rubber with ATH of coupling agent and larger diameter showed better anti-tracking properties. It can be included that ATH of coupling agent use vinyl silane, dispose of tracking characteristic was achieve excellant results.

• Elastomers and Composites
• /
• v.30 no.1
• /
• pp.9-19
• /
• 1995

To make filler loaded conducting rubber which has the excellent electronical and physical properties, CR and NBR were mixed with magnetite$(Fe_3O_4)$. From the result of the study, vulcanization characteristics shows the upgrading curve as increase in filler concentration and CR has more torque than NBR. When elongation be higher, modulus comes to decreases. Tear strength gradually decrease after showing of the maximum point when is in the 100phr in all. Resilience is not good to cause the increase in filler concentration. In the electrical properties, conductivity becomes smaller when filler concentration is increased. The increase of voltage makes an conductivity grown, but the changed rate is weak. The influence of temperature hardly changes on increasing temperature. The morphology and the distribution for a conductivity filler through SEM were better, the more filler concentration increase, the shorter the particle interval is.

• 한국기계연구소 소보
• /
• s.13
• /
• pp.27-43
• /
• 1984

In order to obtain the high resilience, low compression set and less of hardness change in the wiper blade rubber, vulcanization system and receipes must be controlled. To improve the above the above Physical properties, the system should be taken as follows. i) peroxide vulcanization system and sulfur vulcanization system. ii) rubber having more cis-form than trans-form. iii) moderate particle size cabon black. v) usage of other improvement agent. The rubber blade with 4.4% compression set, 76% resilience, Hs 0 $\pm$ 2 hardness change could be abtained through vulcanization system, In addition, the surface of wiper blade must be treated by chemically and physically to minimize for the skid and friction.

• Elastomers and Composites
• /
• v.28 no.4
• /
• pp.267-273
• /
• 1993

A number of hydrophilic acrylic comonomers were incorporated into styrene-butadiene soap-free emulsion polymerization. It was found that reaction rate decreased according to : AN>AA>MMA>EA>IA>AAM>MA>HEMA. It was also observed that reaction rate increased with decreasing H-bonding factor contribution to the solubility parameter of the hydrophilic comonoer. The SBR latexes were very monodisperse with the particle size distribution of $1.03{\times}1.12$. Since growth rate is proportional to polymerization time, the difference in conversion rates between various comonomers was resulted from the particle number density of SBR latexes for the various hydrophilic comonomers. It was also found that the colloidal stability of the latexes was excellent because no external emulsifier was incorporated.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.8
• /
• pp.125-135
• /
• 2008

Rigid-soft particle mixtures, which consist of sand and rubber, are investigated for the understanding of the stress-deformation and elastic moduli. Specimens are prepared with various size ratio sr between sand and rubber particles, and different volumetric sand fraction sf. Small strain shear waves are measured under $K_o$-loading condition incorporated with the stress-deformation test by using oedometer cell with bender elements. The stress-deformation and small strain shear wave characteristics of rigid-soft particle mixtures show the transition from a rigid particle behavior regime to a soft particle behavior regime under fixed size ratio. A sudden rise of $\Lambda$ factor and the maximum value of the $\zeta$ exponent in $G_{max}=\;{\Lambda}({\sigma}'_{o}/kPa)^{\zeta}$ are observed at $sf\;{\approx}\;0.4{\sim}0.6$ regardless of the size ratio sf. Transition mixture shows high sensitivity to confining stress. The volume fraction for the minimum porosity may depend on the applied stress level in the rigid-soft particle mixtures because the soft rubber particles easily distort under load. In this experimental study, the size ratio and volumetric sand fraction are the important factors which determine the behavior of rigid and soft particle mixtures.