Morphology and Crystallization Behavior of Lightly Crosslinked Natural Rubber in Blend

2003 ◽  
Vol 76 (5) ◽  
pp. 1164-1176 ◽  
Author(s):  
Tetsuji Kawazura ◽  
Seiichi Kawahara ◽  
Yoshinobu Isono
Keyword(s):  
Natural Rubber ◽  
Homogeneous Nucleation ◽  
Crosslink Density ◽  
Model Compound ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Gel Content ◽  
Gel Fraction ◽  
Compound Model ◽  
Styrene Butadiene

Abstract Isothermal crystallization of natural rubber (NR) dispersed in styrene-butadiene rubber (SBR) was made at −25 °C to investigate effects of both gel fraction of the rubber and morphology of the blend on the crystallization. NR, thus used, was lightly crosslinked model compound (model-NR), which was cured with dicumylperoxide at 160 °C after mastication. The model-NR was mechanically mixed with a large amount of SBR to form droplets of the rubber, a size of which was dependent upon both gel content and crosslink density of the gel fraction. The crystallization of the model-NR in the droplets was quite slow, corresponding to the level reported in the previous work. A rate of crystallization and Avrami exponent were dependent upon the size of the droplets, but not on the gel content and the crosslink density of the model-NR. The suppression in the crystallization was attributed to the homogeneous nucleation occurring in the droplets. This finding was proved, using rubbers obtained from two clones of Hevea brasiliensis, i.e. RRIM600 and RRIM2025, respectively.

Ultrasonic Devulcanization of SBR Rubber: Experimentation and Modeling Based on Cavitation and Percolation Theories

1998 ◽  
Vol 71 (2) ◽  
pp. 168-190 ◽  
Author(s):  
S. P. Yushanov ◽  
A. I. Isayev ◽  
S. H. Kim
Keyword(s):  
Shear Rate ◽  
Crosslink Density ◽  
Ultrasonic Waves ◽  
Velocity Shear ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Gel Fraction ◽  
Dependent Viscosity ◽  
Styrene Butadiene ◽  
Unique Relationship

Abstract Continuous ultrasonic devulcanization of styrene-butadiene rubber (SBR) is considered. Experiments are performed under various processing conditions. Two recipes of SBR with different amounts of polysulfidic linkages are utilized. Gel fraction and crosslink density of devulcanized rubbers are measured and a unique relationship between them is established. This relationship is found to be in agreement with the 3D percolation theory. Die characteristics with and without imposition of ultrasonic waves are determined. A modification of acoustic cavitation and flow modeling of ultrasonic devulcanization of SBR is proposed using a concept of effective viscosity characterizing the flow of vulcanized particles before devulcanization combined with a shear rate, temperature, and gel fraction dependent viscosity of devulcanized rubber. Velocity, shear rate, pressure, and temperature field along with gel fraction, crosslink density, and number of bonds broken are simulated. Predicted data on gel fraction, crosslink density, amount of poly-, di- and monosulfidic bonds, and pressure are found to be in qualitative agreement with experimental data.

scholarly journals CURE CHARACTERISTICS AND CROSSLINK DENSITY OF NATURAL RUBBER/STYRENE BUTADIENE RUBBER BLENDS

2015 ◽  
Vol 3 (4) ◽  
pp. 1-5
Author(s):  
Indra Surya ◽  
Syahrul Fauzi Siregar
Keyword(s):  
Natural Rubber ◽  
Crosslink Density ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Blend Ratio ◽  
Rubber Blends ◽  
Cure Characteristics ◽  
Rubber Compounds ◽  
Cure Time ◽  
Styrene Butadiene

By using a semi-efficient vulcanization system, the cure characteristics and crosslink density of natural rubber/styrene butadiene rubber (NR/SBR) blends were studied with a blend ratio from 0 to 100% rubber. The scorch time, optimum cure time, and torque difference value of the blended rubber compounds were determined by using the Moving-Die Rheometer (MDR 2000). The crosslink density was determined by the Flory—Rehner approach. Results indicate that the scorch and cure times, ts2 and t90, of the NR/SBR blends increased with increasing the SBR content. Whilst, the maximum values of torque difference and crosslink density were performed by the NR/SBR blend with a blend ratio of 75/25.

Effect of Recycled Nitrile Glove (rNBRg) Particle Sizes on Curing Characteristics and Physical Properties of Natural Rubber/Styrene Butadiene Rubber/Recycled Nitrile Glove (NR/SBR/rNBRg) Blends

2015 ◽  
Vol 815 ◽  
pp. 54-58 ◽  
Author(s):  
N.Z. Nik Yahya ◽  
Nik Noriman Zulkepli ◽  
Hussin Kamarudin ◽  
Hanafi Ismail ◽  
Sam Sung Ting ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Crosslink Density ◽  
Styrene Butadiene Rubber ◽  
Particle Sizes ◽  
Butadiene Rubber ◽  
Maximum Torque ◽  
Curing Characteristics ◽  
Cure Time ◽  
Styrene Butadiene ◽  
Minimum Torque

Effects of different particle sizes of recycled nitrile glove (rNBRg) on curing characteristics and physical properties of natural rubber/styrene butadiene rubber/recycled nitrile glove (NR/SBR/rNBRg) blends were studied. The particle sizes of rNBRg were differentiated by the method of producing. S1 was obtained by cutting the rNBRg (whole glove) into smaller sheet; S2 was obtained by passing rNBRg through 2 rolls mill for 10 times; S3 was obtained by passing rNBRg through 2 rolls mill for 10 times and then mechanically grinded. NR/SBR/rNBRg blends were prepared at 50/30/20 composition using two roll mill at room temperature, with different particle sizes, rNBRg (S1), rNBRg (S2) and rNBRg (S3). Scorch time, cure time, minimum torque, maximum torque, crosslink density and hardness of the blends were examined. Results indicated that scorch time, cure time and minimum torque decreased as the rNBRg particle size decreased, while maximum torque and crosslink density increased. The rigidity of NR/SBR/rNBRg blends increased when smaller rNBRg particles were used, which explained the increased in hardness and decreased in resilience of the blends.

COMPARISON OF THE STRENGTH OF NORMAL AND EDGE-CUT TENSILE SPECIMENS OF STYRENE–BUTADIENE RUBBER AND NATURAL RUBBER WITH SIMILAR CROSSLINK DENSITY

2016 ◽  
Vol 89 (4) ◽  
pp. 631-639 ◽  
Author(s):  
G. Rong ◽  
G. R. Hamed ◽  
J. Jiang
Keyword(s):  
Natural Rubber ◽  
Crosslink Density ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Breaking Strain ◽  
Test Pieces ◽  
Steady Decrease ◽  
Order Of Magnitude ◽  
Cut Depth ◽  
Styrene Butadiene

ABSTRACT Edge cuts of various depths, c, were introduced into tensile specimens of similarly crosslinked (ρc ≈ 6 (10−5) moles of crosslinks/mL) gum (unfilled) natural rubber (NR) and gum styrene–butadiene rubber (SBR). When specimens contained no intentional cut (c = 0, i.e., normal tensile strength), the NR is about 10 times as strong as the SBR. This difference is due to the stereoregularity (cis-1,4-polyisoprene) of NR, enabling it to strain crystallize when deformed. On the other hand, SBR has an irregular, amorphous microstructure that renders it incapable of crystallization. However, for test pieces that contain an edge cut, the strength, σbc, of the NR relative to that of the SBR depends strongly on cut depth. When c ≈ 0.2 mm, the strength of both vulcanizates is reduced about 50%, and hence the ratio of strengths remains about an order of magnitude. But, with a further increase in c, the SBR exhibits a steady decrease in σbc, while the strength of the NR drops discontinuously by nearly a factor of four when c ≈ 1.7 mm. Now, the NR is only about two and one half times as strong as the SBR. Extrapolation of σbc to larger c results in a predicted cut depth c ≈ 4.3 mm, at which the strength of the NR and SBR would be similar. At sufficiently large cut depth, it appears that strain rate at the cut tip is high enough and breaking strain low enough that rupture occurs before significant strain crystallization commences.

Tensile Behavior after Oxidative Aging of Gum and Black-Filled Vulcanizates of SBR and NR

1999 ◽  
Vol 72 (4) ◽  
pp. 721-730 ◽  
Author(s):  
G. R. Hamed ◽  
J. Zhao
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Tensile Behavior ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Oxidative Aging ◽  
Prolonged Aging ◽  
Aging Period ◽  
Early Aging ◽  
Styrene Butadiene

Abstract Typical sulfur-cured vulcanizates of styrene-butadiene rubber (SBR) and natural rubber (NR) were prepared, and subjected to air-oven aging at 100 °C. Gum specimens exhibited an initial aging period in which stiffness was unchanged, while tensile strength and strain-to-break were significantly reduced. In contrast, black-filled vulcanizates stiffened during early aging. After intermediate aging times, NR specimens softened, while SBR stiffened. With prolonged aging, all compositions became hard and inextensible.

Novel modification of styrene butadiene rubber/acrylic rubber blends to improve mechanical, dynamic mechanical, and swelling behavior for oil sealing applications

2021 ◽  
pp. 096739112110313
Author(s):  
Ahmed Abdel-Hakim ◽  
Soma A el-Mogy ◽  
Ahmed I Abou-Kandil
Keyword(s):  
Mechanical Properties ◽  
Crosslink Density ◽  
Physical And Mechanical Properties ◽  
Dynamic Mechanical Properties ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Rubber Blends ◽  
Dynamic Mechanical ◽  
Oil Resistance ◽  
Styrene Butadiene

Blending of rubber is an important route to modify properties of individual elastomeric components in order to obtain optimum chemical, physical, and mechanical properties. In this study, a novel modification of styrene butadiene rubber (SBR) is made by employing acrylic rubber (ACM) to obtain blends of outstanding mechanical, dynamic, and oil resistance properties. In order to achieve those properties, we used a unique vulcanizing system that improves the crosslink density between both polymers and enhances the dynamic mechanical properties as well as its resistance to both motor and break oils. Static mechanical measurements, tensile strength, elongation at break, and hardness are improved together with dynamic mechanical properties investigated using dynamic mechanical analyses. We also proposed a mechanism for the improvement of crosslink density and consequently oil resistance properties. This opens new opportunities for using SBR/ACM blends in oil sealing applications that requires rigorous mechanical and dynamic mechanical properties.

Thermal conductivity of styrene butadiene rubber compounds with natural rubber prophylactics waste as filler

1999 ◽  
Vol 35 (9) ◽  
pp. 1687-1693 ◽  
Author(s):  
N.S. Saxena ◽  
P. Pradeep ◽  
G. Mathew ◽  
S. Thomas ◽  
M. Gustafsson ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Natural Rubber ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Rubber Compounds ◽  
Styrene Butadiene
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