Special issue "Recent rubber ingredient. I". Organic peroxide crosslinking agent.

NORIHISA UJIKAWA

doi:10.2324/gomu.63.616

Mechanism of Peroxide Vulcanization of Elastomers

Rubber Chemistry and Technology ◽

10.5254/1.3539040 ◽

1967 ◽

Vol 40 (1) ◽

pp. 149-176 ◽

Cited By ~ 83

Author(s):

L. D. Loan

Keyword(s):

Crosslinking Agent ◽

Basic Mechanism ◽

Organic Peroxide ◽

Detailed Examination ◽

Recent Book ◽

Operational Conditions ◽

The Subject ◽

Curing Agents ◽

The Common ◽

Technological Evaluation

Abstract As is now well known, the use of an organic peroxide as a crosslinking agent for an elastomer was first reported by Ostromislensky in 1915. In this work benzoyl peroxide was used to cure natural rubber; similar acyl peroxides together with more recently discovered, less active, and more convenient dialkyl peroxides have since this time been used to crosslink a very large number of polymers. With the common unsaturated polymers the vulcanizates produced have mechanical properties rather inferior to those obtained with accelerated sulfur cures. They do, however, have the good aging and low compression set properties which are, in general, associated with sulfurless cures. The commercial use of peroxides in unsaturated elastomers is nevertheless small, being employed only where the presence of sulfur would be deleterious. In spite of its technological disadvantages peroxide crosslinking has been extensively studied since it forms a chemically simple means of introducing crosslinks into a wide variety of rubbers and leads to vulcanizates of simple structure with physically and chemically stable, carbon-to-carbon crosslinks. Interest in the industrial use of peroxides as curing agents has increased recently with the introduction of a number of fully saturated rubbers for which the usual accelerated sulfur systems are unsuitable. Such saturated rubbers are, in general, more resistant to aging, are more thermally stable, and will probably be used to increasingly greater extents as operational conditions become more and more severe. The study of curing systems available for use with such rubbers is therefore of considerable importance and organic peroxides, forming one such system, are worthy of detailed examination. Much work has been done on the technological evaluation of peroxide vulcanizates and much of this is summarized in a recent book edited by Alliger and Sjothun which is recommended as a source of references for a more detailed study of this aspect of the subject. The basic mechanism of the peroxide crosslinking of a wide variety of rubbers has, however, been neglected until relatively recently. For this reason, and for reasons of length, it is proposed to limit the present review to this latter aspect of the subject.

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TPV: A New Insight on the Rubber Morphology and Mechanic/Elastic Properties

Polymers ◽

10.3390/polym12102315 ◽

2020 ◽

Vol 12 (10) ◽

pp. 2315

Author(s):

Cindy Le Hel ◽

Véronique Bounor-Legaré ◽

Mathilde Catherin ◽

Antoine Lucas ◽

Anthony Thèvenon ◽

...

Keyword(s):

Carbon Black ◽

Crosslinking Agent ◽

Domain Size ◽

Organic Peroxide ◽

Packing Fraction ◽

Crosslinking Reaction ◽

High Concentration ◽

Compression Set ◽

Thermoplastic Matrix ◽

Rubber Phase

The objective of this work is to study the influence of the ratio between the elastomer (EPDM) phase and the thermoplastic phase (PP) in thermoplastic vulcanizates (TPVs) as well as the associated morphology of the compression set of the material. First, from a study of the literature, it is concluded that the rubber phase must be dispersed with a large distribution of the domain size in the thermoplastic phase in order to achieve a high concentration, i.e., a maximal packing fraction close to ~0.80. From this discussion, it is inferred that a certain degree of progress in the crosslinking reaction must be reached when the thermoplastic phase is melted during mixing in order to achieve dispersion of the elastomeric phase in the thermoplastic matrix under maximum stress. In terms of elasticity recovery which is measured from the compression set experiment, it is observed that the crosslinking agent nature (DCP or phenolic resin) has no influence in the case of a TPV compared with a pure crosslinked EPDM system. Then, the TPV morphology and the rubber phase concentration are the first order parameters in the compression set of TPVs. Finally, the addition of carbon black fillers leads to an improvement of the mechanical properties at break for the low PP concentration (20%). However, the localization of carbon black depends on the crosslinking chemistry nature. With radical chemistry by organic peroxide decomposition, carbon black is located at the interface of EPDM and PP acting as a compatibilizer.

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