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The use of TEMPO derivatives to improve the adhesion of fibres to elastomer compounds and to inhibit black scorch

IP.com Disclosure Number: IPCOM000191242D
Publication Date: 2009-Dec-22
Document File: 8 page(s) / 191K

Publishing Venue

The IP.com Prior Art Database

Abstract

Fibres such as p-aramid fibres are used to reinforce belts and hoses made with EPDM, to increase the stiffness of the elastomer. This paper describes that the addition of hydroxy-TEMPO to the peroxide-cured elastomer compound significantly increases the reinforcement effect of the fibres in the elastomer compound. It has further been found that hydroxy-TEMPO can prevent the formation of black scorch in EPDM compounds, which is of wide industrial utility. This paper also describes a useful method of preparing a masterbatch of hydroxy-TEMPO and derivatives in apolar polymers that reduces the problems of migration often seen in such masterbatches.

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The use of TEMPO derivatives to improve the adhesion of fibres to elastomer compounds and to inhibit black scorch.

Abstract

Fibres such as p-aramid fibres are used to reinforce belts and hoses made with EPDM, to increase the stiffness of the elastomer.  This paper describes that the addition of hydroxy-TEMPO to the peroxide-cured elastomer compound significantly increases the reinforcement effect of the fibres in the elastomer compound.  It has further been found that hydroxy-TEMPO can prevent the formation of black scorch in EPDM compounds, which is of wide industrial utility.  This paper also describes a useful method of preparing a masterbatch of hydroxy-TEMPO and derivatives in apolar polymers that reduces the problems of migration often seen in such masterbatches.

Introduction

TEMPO, 2,2,6,6-tetramethylpiperidine-1-oxyl, and its derivatives are useful in many reactions as radical traps.  For instance, reference 1[i] describes the use of TEMPO and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (H-TEMPO) as scorch retarders in the peroxide crosslinking of polyolefins.  Scorch is a term that describes the premature build-up of molecular weight during crosslinking processes.  The TEMPO acts to “quench” free radicals during the initial stages of crosslinking, preventing premature build-up of molecular weight.  In this way, gels and processing defects can be eliminated with only minor cost to the ultimate crosslink density of the polymer.  In reference 2[ii], further TEMPO derivatives, such as ester-, ether- or urethane- substituted TEMPO molecules are described with similar scorch-retardant properties and with reduced tendency to migration and volatility.  Proprietary scorch retarding chemical compositions for peroxide cure are commercially available from the Arkema[iii] and from Sartomer[iv] companies.

In this paper, we describe how TEMPO derivatives can have a useful effect in fibre-reinforced composites, by acting to couple fibres into the polymer matrix. 

Aramid fibre masterbatches are used to reinforce compounds for use in extruded hoses such as automotive coolant hoses made with EPDM, especially those produced via the moving die process to produce a shaped hose with bends in three dimensions.  Belts for power transfer are also reinforced with aramid fibres.  The fibres increase the stiffness of the composite in the direction of orientation.   As a side-effect, it is found that the addition of TEMPO and its derivatives also decreases the tendency of some compounds to undergo “black scorch” as described later in this paper.

EPDM is used in the manufacture of automotive V-belts because of its resistance to oxidative and thermal aging.  Such compounds are often reinforced with short fibres, and the fibres are oriented in a preferred direction via a calendaring process.  The reinforce...