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.

Elastic Response of Rubber Double Networks

1999 ◽  
Author(s):  
C. M. Roland ◽  
P. G. Santangelo ◽  
P. H. Mott
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Crosslink Density ◽  
The Other ◽  
Elastic Response ◽  
Double Network ◽  
Mechanical Fatigue ◽  
Equilibrium Modulus ◽  
Failure Properties ◽  
Double Networks

Abstract Double network elastomers are formed by twice-curing rubber, the second time while the material is deformed. When measured parallel to the curing deformation, the equilibrium modulus of a double network exceeds that of an isotropic elastomer of equal crosslink density. This difference increases with increasing strain. Despite the higher modulus, the mechanical fatigue lifetimes of double networks of natural rubber were found to be as much as a factor of ten higher than for the conventionally crosslinked rubber. The double network’s tensile strength, on the other hand, was slightly lower. Such results suggest 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.

Failure Properties of Natural Rubber Double Networks

1995 ◽  
Vol 68 (1) ◽  
pp. 124-131 ◽  
Author(s):  
P. G. Santangelo ◽  
C. M. Roland
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Crosslink Density ◽  
The Other ◽  
Direction Transverse ◽  
Mechanical Fatigue ◽  
Other Hand ◽  
Failure Properties ◽  
The Difference ◽  
Double Networks

Abstract When measured parallel to the curing deformation, double networks of natural rubber have a higher modulus than single networks of equal crosslink density. The difference is greater at higher strains. Despite the higher modulus, the mechanical fatigue lifetimes of double networks were found to be as much as a factor of ten higher than for conventionally crosslinked NR. The double network's tensile strength, on the other hand, was slightly lower. In contrast to these results, the modulus and tensile strength in the direction transverse to the curing strain are minimally affected by the presence of a composite network.

Orientation Effects in Rubber Double Networks

1990 ◽  
Vol 63 (2) ◽  
pp. 285-297 ◽  
Author(s):  
C. M. Roland ◽  
M. L. Warzel
Keyword(s):  
Network Formation ◽  
Double Network ◽  
Stable Orientation ◽  
Enhanced Strain ◽  
Strain Induced Crystallization ◽  
Failure Properties ◽  
Residual Strains ◽  
Low Levels ◽  
Double Networks ◽  
Rubbery Material

Abstract The utilization of network structure to impart stable orientation to a rubbery material has been largely unexploited to date. It is demonstrated that the presence of a double network will amplify both the modulus and strain crystallizability of an elastomer, presumably without the disadvantages encountered in achieving these through simple increases in crosslink density. The high residual strains obtained via double-network formation are accompanied by surprisingly low levels of birefringence. The extent of molecular orientation necessary to engender high residual strain is evidently quite low, at least in so far as the former is reflected in a bulk macroscopic measurement such as birefringence. This low equilibrium birefringence, along with the absence of any measurable thermal crystallization effects, indicate that double networks are actually not highly oriented. As seen from their higher moduli and higher strain optical coefficients relative to single networks, and from their enhanced strain crystallizability, double networks are evidently very orientable. Investigation of this aspect of the behavior of double networks would likely prove fruitful, not only concerning these materials, but also with regard to obtaining a broader understanding of rubber elasticity. While the enhancement of strain-induced crystallization might suggest that rubbers with double networks will exhibit superior failure properties, this remains to be demonstrated. The crystallization results described herein clearly raise more questions than can presently be answered concerning the behavior of rubbers with double networks.

Tensile and Tear Behavior of Anisotropic Double Networks of a Black-Filled Natural Rubber Vulcanizate

1998 ◽  
Vol 71 (5) ◽  
pp. 846-860 ◽  
Author(s):  
G. R. Hamed ◽  
M. Y. Huang
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Stress Strain ◽  
Double Network ◽  
Extension Ratio ◽  
Rubber Vulcanizate ◽  
Double Networks ◽  
Strain Responses ◽  
Sheet Stretching ◽  
Weakly Dependent

Abstract Double networks of a black-filled natural rubber composition have been prepared by partially curing a sheet, stretching it, and then completing cure. Upon release, a double network retracts to a residual extension ratio, αr. Samples cut perpendicular to the stretch direction have stress—strain responses like the isotropic single network, while parallel samples have enhanced stiffness and tensile strength, and reduced extensibility. Tensile strength is rather weakly dependent on αr. Tear strengths of the double networks, determined using edge-cut strip specimens, exceed that of the single network for low αr. However, when αr is high, double networks have very low tear strengths. Consistent with previous studies, high tear strengths are associated with extensive longitudinal cracking.

Physical Properties of Rice Husk Fiber/Natural Rubber Composites

2011 ◽  
Vol 410 ◽  
pp. 90-93 ◽  
Author(s):  
Ladawan Srisuwan ◽  
Kasama Jarukumjorn ◽  
Nitinat Suppakarn
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Rice Husk ◽  
Crosslink Density ◽  
Morphological Properties ◽  
Rubber Composites ◽  
Elongation At Break ◽  
Natural Rubber Composites ◽  
Reinforcing Filler

In this study, rice husk fiber (RHF) was used as a reinforcing filler for natural rubber (NR). NR composites were prepared at various RHF contents, i.e., 10, 20, 30, 40 and 50 phr. Sulfur conventional vulcanization was used. Effect of RHF content on cure characteristics, mechanical properties and morphological properties of NR composites were investigated. The results showed that scorch and cure times of RHF/NR composites were not affected by increasing RHF content. Crosslink density, tensile strength, elongation at break and tear strength of NR composites slightly decreased with increasing RHF content whereas M100 and M300 of the composites slightly increased with increasing RHF content.

Aging with Applied Strain of A Black-Filled Natural Rubber Vulcanizate. Part I: Network Changes

2008 ◽  
Vol 81 (4) ◽  
pp. 650-670 ◽  
Author(s):  
Crittenden J. Ohlemacher ◽  
Gary R. Hamed
Keyword(s):  
Natural Rubber ◽  
Crosslink Density ◽  
Network Formation ◽  
Main Chain ◽  
Chain Scission ◽  
Tensile Behavior ◽  
Applied Strain ◽  
Chain Orientation ◽  
Double Network ◽  
Double Networks

Abstract Black-filled natural rubber, with an inefficient sulfur cure, was aged at 90 °C and 110 °C under nitrogen, with and without applied strain. Samples aged under strain became “double networks” and retained a residual extension ratio. The crosslink density of samples passed through a maximum with increasing severity of aging. Presumably this arises because the thermally labile, polysulfidic crosslinks break, and new crosslinks of lower rank form, resulting in increased crosslink density; but, when aged at 110 °C, this is offset by chain scission and other main-chain modifications. For double networks, it is proposed that a second network, which tends to keep samples extended, is formed at the expense of crosslinks in the original, first network. Unaged and single network samples were isotropic in tensile behavior and only slightly anisotropic in swelling behavior. For double networks, swelling and tensile properties were anisotropic, and there was some evidence that parallel specimens have increased ability to strain-crystallize. The observed anisotropies in double networks are proposed to arise from the chain orientation that persisted after double network formation.

Effect of Vulcanization on the Dynamic Properties of Rubber

1959 ◽  
Vol 32 (3) ◽  
pp. 662-667 ◽  
Author(s):  
E. V. Kuvshinskiĭ ◽  
E. A. Sidorovich
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Crosslink Density ◽  
Mechanical Characteristics ◽  
Dynamic Properties ◽  
Thermostatic Control ◽  
Gap Series ◽  
Equilibrium Modulus ◽  
Butadiene Styrene

Abstract It is a known fact that the mechanical properties of rubber depend essentially upon the density (i.e., the crosslink density) of the vulcanization network. The dependence of the “equilibrium” (statistical) modulus of elasticity upon the concentration of crosslinks as well as the dependence of the tensile strength —has been studied in a series of investigations. In contrast to this, analogous investigations of the dynamic mechanical characteristics are practically nonexistent. We have undertaken our present work with the hope of filling this gap. Series of gum compounds were prepared from natural (smoked sheet) and synthetic polyisoprene (SKI), sodium butadiene (SKB), butadiene-styrene (SKS-30A), and butadiene-nitrile (SKN-26) rubbers which varied in their degree of vulcanization. The percentage of sulfur and accelerator were varied as were the temperature and the time of vulcanization. The mechanical-dynamic characteristics of the rubber at a predetermined impact pressure—the rebound elasticity and the dynamic elastic modulus were studied with the pendulum elastometer KS over a temperature range of 20–100° C. The duration of the stress was .03/.05 second. We estimated the concentration of crosslinks in the rubber samples from the magnitude of the equilibrium modulus. In order to determine this characteristic, we compressed specimens which were 20 mm in height and 10 mm in diameter 15% and studied the relaxation of stress. The specimens were also tested on the pendulum elastometer. Heppler's consistometer operating on the lever weight principle, was adapted for our measurements. The experiments were conducted at 60° C, the thermostatic control being effected with the help of Heppler's ultrathermostat.

EFFECT OF ZINC DITHIOCARBAMATES AND THIAZOLE-BASED ACCELERATORS ON THE VULCANIZATION OF NATURAL RUBBER

2012 ◽  
Vol 85 (1) ◽  
pp. 120-131 ◽  
Author(s):  
Md. Najib Alam ◽  
Swapan Kumar Mandal ◽  
Subhas Chandra Debnath
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Reaction Mechanism ◽  
Natural Rubber ◽  
High Performance ◽  
Binary Systems ◽  
Synergistic Activity ◽  
Tetramethylthiuram Disulfide

Abstract Several zinc dithiocarbamates (ZDCs) as accelerator derived from safe amine has been exclusively studied in the presence of thiazole-based accelerators to introduce safe dithiocarbamate in the vulcanization of natural rubber. Comparison has been made between conventional unsafe zinc dimethyldithiocarbamate (ZDMC) with safe novel ZDC combined with thizole-based accelerators in the light of mechanical properties. The study reveals that thiuram disulfide and 2-mercaptobenzothiazole (MBT) are always formed from the reaction either between ZDC and dibenzothiazyledisulfide (MBTS) or between ZDC and N-cyclohexyl-2-benzothiazole sulfenamide (CBS). It has been conclusively proved that MBT generated from MBTS or CBS reacts with ZDC and produces tetramethylthiuram disulfide. The observed synergistic activity has been discussed based on the cure and physical data and explained through the results based on high-performance liquid chromatography and a reaction mechanism. Synergistic activity is observed in all binary systems studied. The highest tensile strength is observed in the zinc (N-benzyl piperazino) dithiocarbamate-accelerated system at 3:6 mM ratios. In respect of tensile strength and modulus value, unsafe ZDMC can be successfully replaced by safe ZDCs in combination with thiazole group containing accelerator.

scholarly journals Composites from Thermoplastic Natural Rubber Reinforced Rubberwood Sawdust: Effects of Sawdust Size and Content on Thermal, Physical, and Mechanical Properties

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Chatree Homkhiew ◽  
Surasit Rawangwong ◽  
Worapong Boonchouytan ◽  
Wiriya Thongruang ◽  
Thanate Ratanawilai
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
High Density Polyethylene ◽  
High Performance ◽  
Physical And Mechanical Properties ◽  
Modulus Of Rupture ◽  
Shore Hardness ◽  
Thermoplastic Natural Rubber ◽  
Plastic Content

The aim of this work is to investigate the effects of rubberwood sawdust (RWS) size and content as well as the ratio of natural rubber (NR)/high-density polyethylene (HDPE) blend on properties of RWS reinforced thermoplastic natural rubber (TPNR) composites. The addition of RWS about 30–50 wt% improved the modulus of the rupture and tensile strength of TPNR composites blending with NR/HDPE ratios of 60/40 and 50/50. TPNR composites reinforced with RWS 80 mesh yielded better tensile strength and modulus of rupture than the composites with RWS 40 mesh. The TPNR/RWS composites with larger HDPE content gave higher tensile, flexural, and Shore hardness properties and thermal stability as well as lower water absorption. The TPNR/RWS composites with larger plastic content were therefore suggested for applications requiring high performance of thermal, physical, and mechanical properties.

Stress Optical Behavior of Rubber Networks at Large Deformations

1966 ◽  
Vol 39 (5) ◽  
pp. 1436-1450
Author(s):  
K. J. Smith ◽  
D. Puett
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Statistical Theory ◽  
Natural Rubber ◽  
Large Deformations ◽  
Strong Support ◽  
Theoretical Development ◽  
Statistical Parameters ◽  
Strain Behavior ◽  
Optical Behavior

Abstract The birefringence of natural rubber networks at large deformations has been investigated experimentally and compared with the simultaneously determined stress—strain behavior. Our data is analyzed using a statistical theory of flexibly jointed chains, derived herein, which is believed to be more significant for the particular range of deformation used than the theories of Treloar and of Kuhn and Grün. In addition, the experimental data of Saunders is commented on in light of our theoretical development. We find that for network extensions exceeding those of the Gaussian region there is little correlation between the observed and theoretical behavior of the stress and birefringence (based upon the theory of flexibly jointed chains) and this lack of agreement is attributed to the fact that the statistical parameters needed for the description of the optical chain properties differ in magnitude from those required for the mechanical properties. Furthermore, by considering the points of incipient crystallization the strain behavior of the stress-optical coefficient is highly indicative of nonGaussian behavior rather than crystallization, and therefore yields strong support for the position that nonGaussian behavior does exist in rubber networks.

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