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

A Physical and Mechanical Study of Prestressed Competitive Double Network Thermoplastic Elastomers

“…This second cross-linked network can be formed within the initial network, as depicted in Figure . This results in materials with unusual and enhanced properties which have been termed “double-network elastomers” in early literature. − Recently, Singh and Lesser have reported the formation of these double network elastomers, where the emphasis was given to understanding the thermal and thermomechanical properties of “thermoplastic” elastomers, − as opposed to traditional chemically cured elastomers which were mainly utilized to understand the aging process and effects of entanglements resulting in permanent set of elastomers under deformation and studying numerous physical and mechanical properties of these elastomers ,− in various deformation modes including uniaxial extension, , equibiaxial extension, and shear …”

“…This results in materials with unusual and enhanced properties which have been termed "double-network elastomers" in early literature. [2][3][4][5][6] Recently, Singh and Lesser have reported the formation of these double network elastomers, where the emphasis was given to understanding the thermal and thermomechanical properties of "thermoplastic" elastomers, [7][8][9][10] as opposed to traditional chemically cured elastomers which were mainly utilized to understand the aging process and effects of entanglements resulting in permanent set of elastomers under deformation and studying numerous physical and mechanical properties of these elastomers 2,[11][12][13][14][15][16][17][18][19][20][21][22] in various deformation modes including uniaxial extension, 23,24 equibiaxial extension, 25 and shear. 26 The double network concept, first introduced more than 50 years ago by Tobolsky et al, 4 was used to explain the physical aging of rubbers, which involved free-radical scission and crosslinking under deformation.…”

Mechanical and thermo‐mechanical studies of double networks based on thermoplastic elastomers

“…In the last 2 decades, many studies probed the physical properties of double networks, with the intent of applying them to practical applications. Properties studied included stress relaxation behavior,24 orientation and crystallization effects,1, 25 electrical conductivity,26 tensile properties,27 fatigue,28 birefringence,29 creep‐recovery,30, 31 swelling,32, 33 failure properties,34 dynamic properties, and filler effects 35. However, little attention has been given to the thermal and thermomechanical behavior, despite their significance in applications such as o ‐rings, actuators, encapsulants, and dampers.…”

Effect of the cure system on aging resistance of natural rubber compounds

“…Similar results have been observed by other authors. 26,29 Monosulfidic links, which are predominant in formulations F3 and F4, under dynamic stress become less resistant and thus the compound F2, vulcanized with MBT/TMTD system, presents the best dynamical behavior. According to the literature, one among various challenges in elastomers technology is the development of formulations with thermal stability while maintaining dynamic performance characteristics.…”