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.

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.

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.

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.

scholarly journals Effects of water absorption on the mechanical properties of hybrid natural fibre/phenol formaldehyde composites

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sekar Sanjeevi ◽  
Vigneshwaran Shanmugam ◽  
Suresh Kumar ◽  
Velmurugan Ganesan ◽  
Gabriel Sas ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Impact Strength ◽  
Water Absorption ◽  
Hybrid Composites ◽  
Phenol Formaldehyde ◽  
Natural Fibre ◽  
The Other ◽  
Fibre Reinforcement ◽  
Dry Conditions

AbstractThis investigation is carried out to understand the effects of water absorption on the mechanical properties of hybrid phenol formaldehyde (PF) composite fabricated with Areca Fine Fibres (AFFs) and Calotropis Gigantea Fibre (CGF). Hybrid CGF/AFF/PF composites were manufactured using the hand layup technique at varying weight percentages of fibre reinforcement (25, 35 and 45%). Hybrid composite having 35 wt.% showed better mechanical properties (tensile strength ca. 59 MPa, flexural strength ca. 73 MPa and impact strength 1.43 kJ/m2) under wet and dry conditions as compared to the other hybrid composites. In general, the inclusion of the fibres enhanced the mechanical properties of neat PF. Increase in the fibre content increased the water absorption, however, after 120 h of immersion, all the composites attained an equilibrium state.

Devulcanization of Automobile Scrap Tyres by a Mechanochemical Process

2005 ◽  
Vol 21 (4) ◽  
pp. 319-331 ◽  
Author(s):  
G.K. Jana ◽  
C.K. Das
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Chemical Process ◽  
Crosslink Density ◽  
Diallyl Disulfide ◽  
Density Data ◽  
Vulcanized Rubber ◽  
Rubber Waste ◽  
Mechanical Shearing ◽  
Vulcanization Process

The de-vulcanization of rubber waste poses a challenging economical, environmental and social problem. We propose a new de-vulcanization process to re-use the rubber waste. It is a mechano-chemical process (MCP), where the waste is de-vulcanized by a combination of mechanical shearing, heat (110 °C) and the use of a de-vulcanizing agent (diallyl disulfide). A new look at the de-vulcanization mechanism and the influence of the de-vulcanizing agent on the mechanical properties of the ultimate re-vulcanized rubber is also presented. One of the most interesting observations is that the retention of tensile strength of the re-vulcanized rubber with respect to the original tyre was 34.9% when de-vulcanized in the absence of diallyl disulfide and 72.4% in its presence. The formation of extra crosslinks in those re-vulcanized rubbers containing disulfide was confirmed from crosslink density data and from TGA results. DMA analysis revealed that the storage modulus also increased for re-vulcanized rubber containing the disulfide.

scholarly journals Correlation between Porosity and Electrical-Mechanical Properties of Carbon Nanotube Buckypaper with Various Porosities

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Ling Liu ◽  
Qiaoxin Yang ◽  
Jingwen Shen
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Carbon Nanotube ◽  
The Other ◽  
Positive Pressure ◽  
Filtration Method ◽  
Elongation At Break ◽  
Conductive Materials ◽  
Wide Range ◽  
Electrical Conductivities

Porous carbon nanotube (CNT) buckypapers (BPs) with various porosities were obtained by using a positive pressure filtration method. The porosity of the BPs fell into a wide range of 11.3–39.3%. Electrical conductivities and tensile mechanical properties of the prepared BPs were then measured and correlated with the porosity of the CNT BPs. Results demonstrated that the conductivities, tensile strength, and elastic modulus of the BPs could decrease by increasing their porosity. The elongation at break of the BPs on the other hand did increase significantly, suggesting improved toughness of the BPs. The obtained electrical conductivity and tensile strength of the porous BPs can reach nearly 0.6 S/m and 26 MPa, respectively, which may be potentially useful in composites reinforcement and conductive materials.

Accelerated Aging Tests of HTPB-Based Propellants

2018 ◽  
pp. 246-271
Author(s):  
Roberta Jachura Rocha
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Crosslink Density ◽  
Aging Process ◽  
Low Cost ◽  
Accelerated Aging ◽  
Solid Propellants ◽  
Launch Vehicles ◽  
Late Twentieth ◽  
Late Twentieth Century

In the late twentieth century, liquid and solid propulsion technologies have been integrated into hybrid engines currently apllied in propulsion launch vehicles and missiles. The reaction of polyol (HTPB) and diisocyanate (IPDI) provides the most versatile of the binders in the production of solid propellants due to its ability to withstand high loads combined with low cost and ease of processing. A propellant based on HTPB obtained in this study was submitted to natural and accelerated aging tests, seeking to evaluate the modifications of mechanical properties as tensile strength, elongation and hardness up to 360 days. The mechanism considered in the aging process is the increase of crosslink density by breaking the double bond contained in the HTPB molecule, which causes the instability of the propellant, increasing its handling risk. Samples of these propellants subjected to aging presented variations in their properties that match the values available in the literature.

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.

Superior Mechanical Properties of Ultrasonically Recycled EPDM Rubber

2003 ◽  
Vol 76 (1) ◽  
pp. 253-270 ◽  
Author(s):  
Jushik Yun ◽  
A. I. Isayev
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Power Consumption ◽  
Crosslink Density ◽  
Dynamic Properties ◽  
Extensive Study ◽  
Processing Conditions ◽  
Elongation At Break ◽  
Epdm Rubber ◽  
Superior Mechanical Properties

Abstract This paper describes the results of an extensive study involving the continuous ultrasonic devulcanization of unfilled EPDM rubber. Die pressure and ultrasound power consumption were measured as a function of processing conditions. The mechanical properties of aged and fresh revulcanized EPDM rubber were measured. Gel fraction, crosslink density, and dynamic properties were also determined for the virgin vulcanizate, the ultrasonically devulcanized rubber, and the revulcanized rubber. Additionally, the cure behavior of virgin and devulcanized EPDM rubber was investigated. The tensile strength of revulcanized EPDM rubber was found to be much higher than that of the virgin vulcanizate with the elongation at break being practically intact. A mechanism explaining the increase in mechanical properties of revulcanized rubbers was proposed.

Effect of Thermal Aging on Mechanical Properties of EPDM Rubber

2015 ◽  
Vol 727-728 ◽  
pp. 318-321 ◽  
Author(s):  
Jie Liu ◽  
Lun Wu Zhang ◽  
Bin Wang ◽  
Ze Qi Xu ◽  
Wan Wang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Electron Microscope ◽  
Thermal Aging ◽  
Crosslink Density ◽  
Aging Process ◽  
Epdm Rubber ◽  
Compressive Testing ◽  
Scanning Electron ◽  
Accelerated Thermal Aging

EPDM rubber was exposed to an accelerated thermal aging environment produced by an air-circulating oven. The changes of morphology, mechanical properties of EPDM were monitored by scanning electron microscope (SEM), tensile/compressive testing. Crosslink density of EPDM was measured by the solvent swell method. The results showed that many cracks and voids appeared on the surface of EPDM with the exposure time. The aging process proceeded predominantly via crosslinking. The tensile strength increased with increase in crosslink density up to a maximum and thereafter decreased with further increase in crosslink density.

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