Mechanical and Swelling Behavior of Double Networked Natural Rubber Cured Using a New Binary Accelerator System

2007 ◽  
Vol 80 (5) ◽  
pp. 809-819 ◽  
Author(s):  
C. V. Marykutty ◽  
G. Mathew ◽  
Sabu Thomas
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Transverse Direction ◽  
Tensile Elongation ◽  
Longitudinal Direction ◽  
Chain Orientation ◽  
Swelling Studies ◽  
Natural Rubber Vulcanizates ◽  
Double Networks ◽  
Accelerator System

Abstract The concept of double networks, which impart chain orientation to elastomers, is a rather new idea. Double networks were induced in natural rubber vulcanizates cured with different accelerator systems. Double networked natural rubber with different extensions cured with N-cyclohexyl benzothiazyl sulphenamide (CBS) and 1-phenyl 5-ortho -tolyl 2,4 dithiobiuret was studied and the effect of extension on the mechanical properties and swelling was analyzed. The extent of chain orientation was analyzed through anisotropic swelling studies. The modulus, tensile strength and tear strength showed an increase with increased residual extension ratio. The effect was more predominant in the longitudinal direction than in the transverse direction. The ultimate tensile elongation showed a slight deterioration. It was revealed that the formation of double networks with higher residual extension ratios restricted the entry of the solvent. Based on the studies it was concluded that residual extension has a profound effect in determining the final properties of vulcanizates.

HXNBR Coating for Improving Aging Resistance of Natural Rubber Products

2006 ◽  
Vol 79 (4) ◽  
pp. 553-560 ◽  
Author(s):  
Rani Joseph
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Room Temperature ◽  
Oxidative Degradation ◽  
Thin Coating ◽  
Oil Resistance ◽  
Aging Resistance ◽  
Natural Rubber Vulcanizates ◽  
Good Heat ◽  
Accelerator System

Abstract HXNBR (Hydrogenated Carboxylated Nitrile Rubber) has very good heat ageing resistance and oil resistance. A novel accelerator system is designed to bring about the vulcanization of HXNBR at room temperature. The room temperature cured samples showed good mechanical properties equivalent to those of high (150 °C) temperature cured samples. Natural rubber vulcanizates are highly prone to oxidative and ozone degradation. The oil resistance of natural rubber vulcanizates is also very low. The oil resistance, ozone and oxidative degradation resistance of natural rubber vulcanizates are considerably improved by placing a thin coating of HXNBR over it.

Mechanism of the Crystallization of High Polymers

1954 ◽  
Vol 27 (2) ◽  
pp. 374-384 ◽  
Author(s):  
G. Schuur
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Amorphous Material ◽  
Crystalline Polymer ◽  
Longitudinal Direction ◽  
Crystalline Material ◽  
Current View ◽  
X Ray ◽  
Made In ◽  
High Polymers

Abstract The crystallization of higher polymers is a phenomenon which is not yet fully understood, one of the main difficulties being to explain how the spherulites arise. An attempt will be made in this paper to draw a clearer picture of the mechanism of crystallization and thus to account for the origin of spherulites. It will then be seen how several other phenomena involved in the crystallization of natural rubber can be shown to be logically interrelated. The current view is that a crystalline polymer consists of a continuous amorphous phase containing small crystalline regions, the crystallites. The evidence as to the size of these crystallites, however, is at present inconclusive, because only the lower limit of their size can be measured by means of x-ray examination. The reason is that, owing to the absence of reflections of a higher order, the effect of irregularities in the crystallites and of the heat motion of the molecules cannot be measured separately. Another doubtful question is whether the small angle interference maxima are to be interpreted as a measure of mean distances between the crystallites. To do this, Wallner has to resort to the assumption that the crystallites are unstable, whereas it is presumed, on the evidence of the mechanical properties of the high polymers, that a crystallite is stable and permanent. Hoffmann found 82 ± 7 per cent of crystalline material in polychlorotrifluoroethylene and Buckley, Cross, and Ray found as much as 95 per cent in polymethylene. Such high percentages make it doubtful whether the crystalline phase can be discontinuous at all. In this article any volume of material in which the molecules lie parallel is called a crystallite. The direction in which the molecules are oriented is termed the longitudinal direction of the crystallite. It is immaterial to the argument whether a crystallite consists of several crystallites, aligned in parallel separated by a small amount of amorphous material, or of a single crystallite containing large irregularities.

Kinetics of Crosslinking and Network Changes in Natural Rubber Vulcanizates with a Dithiodimorpholine Based Accelerator System

1980 ◽  
Vol 53 (5) ◽  
pp. 1015-1022 ◽  
Author(s):  
A. K. Bhowmick ◽  
S. K. De
Keyword(s):  
Natural Rubber ◽  
Rate Constants ◽  
Crosslink Density ◽  
Curing Temperature ◽  
Side Reactions ◽  
Filler Surface ◽  
Natural Rubber Vulcanizates ◽  
Kinetics Of ◽  
Accelerator System

Abstract Kinetics of crosslinking and network changes in unfilled and filled natural rubber vulcanizates with a dithiodimorpholine based accelerator system have been studied at 150° and 180°C. Results show that addition of HAF black enhances the polysulfidic crosslinks as well as the total crosslinks. This has been explained with the help of Coran's model wherein HAK black increases the rate constants. It is likely that the filler surface prevents desulfuration and undesirable side reactions involving the crosslink precursors. Increase of curing temperature by 30°C lowers the total crosslink density and increases the sulfur inefficiency.

Improving oxidation stability and mechanical properties of natural rubber vulcanizates filled with calcium carbonate modified by gallic acid

2010 ◽  
Vol 66 (7) ◽  
pp. 965-977 ◽  
Author(s):  
Sirilux Poompradub ◽  
Thirapat Luthikaviboon ◽  
Srisuwan Linpoo ◽  
Rojrit Rojanathanes ◽  
Pattarapan Prasassarakich
Keyword(s):  
Mechanical Properties ◽  
Calcium Carbonate ◽  
Natural Rubber ◽  
Gallic Acid ◽  
Oxidation Stability ◽  
Natural Rubber Vulcanizates

scholarly journals Assessment of the Spatial Distribution of Mechanical Properties of the Tissue of Anterior Abdominal Wall at Maximum Functional Load

2021 ◽  
Vol 6 (3) ◽  
pp. 175-181
Author(s):  
R. B. Lysenko ◽  
◽  
V. I. Lіakhovskyi ◽  
V. R. Lysenko
Keyword(s):  
Mechanical Properties ◽  
Spatial Distribution ◽  
Abdominal Wall ◽  
Transverse Direction ◽  
Anterior Abdominal Wall ◽  
Longitudinal Direction ◽  
Main Group ◽  
Treatment Center ◽  
Control Group ◽  
White Line

The purpose of the study was to investigate the changes in the mechanical properties of the anterior abdominal wall at maximum functional loads. Materials and methods. The study was conducted on 112 volunteers aged 18 to 49 years old who were examined and treated in the surgical department of the Medical Diagnostic and Treatment Center "Medion" Poltava for the period from June 2020 to May 2021. There were 60 women (53.6 %), and 52 (46.4%) men. Volunteers were divided into 2 groups: the main group (n=58), which underwent the analysis of movement and deformation changes of the anterior abdominal wall during maximal abdominal inflation during the examination, and the control group (n=54), which were operated laparoscopically due to the schedule. Results and discussion. The results of the study showed the following changes in the mechanical properties of the tissues of the anterior abdominal wall: the average deformation in the longitudinal direction was 6% in the main group and 12% in the control one; deformations in the transverse direction were 3% in the main group and 8% in the control group; deformation in the longitudinal direction exceeded the deformation in the transverse by 38-54% (on average by 46%); the area of the anterior abdominal wall in the main group increased by 10%, and in the control one – by 22% (on average by 16%). During the studies, the anterior abdominal wall underwent greater stresses in the transverse orientation than in the longitudinal one (anisotropy coefficient ~2). The Young's modulus of anterior abdominal wall in the sagittal plane is defined as 23.5±2.6 kPa, while in the transverse – 42.5±7.0 kPa. The mechanical properties of human anterior abdominal wall tissues differed along and across the white line of the abdomen: the modulus of elasticity of anterior abdominal wall tissues, with the same force of impact, in the longitudinal direction is less than the transverse average of 44% (p >0.05). That is, the longitudinal stiffness of the anterior abdominal wall is lower than the transverse one. The maximum strength of the anterior abdominal wall is across the white line of the abdomen, and the greatest elasticity – along. The anterior abdominal wall in women showed increased elasticity compared to men, while the stiffness of the anterior abdominal wall tissue in men in both directions was statistically significantly higher than in women (p >0.05). Conclusion. Reconstruction of the spatial distribution of the mechanical properties of anterior abdominal wall tissues according to the nature of their deformation at maximum functional loads provides an additional opportunity to assess the biomechanics of anterior abdominal wall. The mechanical properties of the musculo-aponeurotic structures of anterior abdominal wall in humans differ in the longitudinal and transverse directions. They have the greatest elasticity in the longitudinal direction, and the maximum rigidity and strength in the transverse direction. The strength of the anterior abdominal wall tissue in men is higher, and the elasticity is less than in women. Changes in the mechanical anisotropic characteristics of anterior abdominal wall tissues at maximum functional loads should be taken into account when performing the anterior abdominal wall alloplasty technique

The Mechanical Behavior of Double Network Elastomers

1994 ◽  
Vol 67 (2) ◽  
pp. 359-365 ◽  
Author(s):  
P. G. Santangelo ◽  
C. M. Roland
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Crosslink Density ◽  
Double Network ◽  
Equilibrium Modulus ◽  
Failure Properties ◽  
Residual Strains ◽  
Double Networks

Abstract It was found that at low residual strains, the modulus of double network rubbers can be less than that of an isotropic elastomer of equal crosslink density. At higher residual strains, the equilibrium modulus is higher for the double network. This aspect of the behavior of networks was investigated using two phenomenological descriptions of rubber elasticity, the Mooney-Rivlin (MR) and the Roth, Martin, and Stiehler (RMS) Equations. Calculations using either approach, which make use of the independent network hypothesis, were qualitatively in agreement with the experimental data. The tensile strength of double networks based on natural rubber were found to be independent of the amount of residual strain. This is true even at higher residual strains, wherein the modulus is significantly amplified. This suggests that the conventional compromise between modulus and failure properties can be circumvented using double network rubbers. Their utilization can yield elastomers of better mechanical properties.

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