Resistance to Ozone Cracking in Elastomer Blends

1967 ◽  
Vol 40 (2) ◽  
pp. 635-649 ◽  
Author(s):  
E. H. Andrews
Keyword(s):  
Phase Separation ◽  
Natural Rubber ◽  
Crack Density ◽  
Stored Energy ◽  
Ethylene Propylene ◽  
Blend Composition ◽  
Inert Particles ◽  
Ethylene Propylene Rubber ◽  
Electron Microscopical

Abstract The phenomenon of ozone cracking has been investigated for elastomer blends containing an ozone reactive phase (natural rubber) and an ozone inert phase (ethylene propylene rubber). Electron microscopical studies reveal phase separation in the blend and the locus of ozone attack. Ozone cracks traverse the reactive phase and occasionally jump across inert particles without severing them. This mechanism provides the basis of a theory which correctly predicts the dependence of both the critical stored energy for ozone cracking and the crack density upon the blend composition.

Use of C14 Tagged Cumyl Peroxide to Study Peroxide Vulcanization of Ethylene Propylene Copolymers

1966 ◽  
Vol 39 (3) ◽  
pp. 521-523 ◽  
Author(s):  
G. Ballini ◽  
L. Baldi ◽  
E. DiGiulio
Keyword(s):  
Natural Rubber ◽  
Decomposition Products ◽  
Ethylene Propylene ◽  
Polymer Molecules ◽  
Peroxide Decomposition ◽  
Ethylene Propylene Rubber ◽  
Carbon Bonds ◽  
Chemical Scheme ◽  
Crosslinking Agents

Abstract Peroxides are used today as crosslinking agents for elastomers in general, and for saturated elastomers in particular. Among peroxides, cumyl peroxide merits special attention because of the small danger in handling since it decomposes appreciably only above 120–130° C. The mechanism of the vulcanization reaction has been considered very simple, leading to the formation of carbon-to-carbon bonds between polymer molecules. The path of the reaction can be followed if one can determine at every instant the amount of crosslinking and of peroxide decomposition products, or the quantity of residual peroxide. From the existing literature, it appears evident that the degree of crosslinking in natural rubber and the recovery of peroxide fragments justify the reactions proposed in the chemical scheme. However, in the case of ethylene propylene rubber these lead to the conclusion that the peroxide is only partly used. This different fate of cumyl peroxide, depending on whether the decomposition occurs in natural rubber or in an ethylene propylene copolymer, demonstrates that other reactions occur, which involve primary peroxide radicals or the secondary polymeric radicals, or both, in a manner different from the proposed scheme.

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