Enhancement of EPDM Crosslinked Elastic Properties by Association of Both Covalent and Ionic Networks.

Chloé Larrue,Philippe Cassagnau,Véronique Bounor-Legaré

doi:10.3390/polym13183161

Abstract

The objective of this study was to replace elastomer crosslinking based on chemical covalent bonds by reversible systems under processing. One way is based on ionic bonds creation, which allows a physical crosslinking while keeping the process reversibility. However, due to the weak elasticity recovery of such a physical network after a long period of compression, the combination of both physical and chemical networks was studied. In that frame, an ethylene-propylene-diene terpolymer grafted with maleic anhydride (EPDM-g-MA) was crosslinked with metal salts and/or dicumyl peroxide (DCP). Thus, the influence of these two types of crosslinking networks and their combination were studied in detail in terms of compression set. The second part of this work was focused on the influence of different metallic salts (KOH, ZnAc2) and the sensitivity to the water of the physical crosslinking network. Finally, the combination of ionic and covalent network allowed combining the processability and better mechanical properties in terms of recovery elasticity. KAc proved to be the best ionic candidate to avoid water degradation of the ionic network and then to preserve the elasticity recovery properties under aging.

Highlights

The challenge of obtaining elastomers’ reversible crosslinking to meet classical thermoplastics melt processing is elegant and of importance in terms of industrial applications and circular economy
The objective of this work was to improve the mechanical properties of an ethylene-propylene-diene terpolymer (EPDM)-gMA while keeping the processability of the samples
It can be noticed for all the salts used, except for NaAc, that the water treatment in our experimental conditions has no influence on the compression set (Figure 10b)

Summary

Introduction

The challenge of obtaining elastomers’ reversible crosslinking to meet classical thermoplastics melt processing is elegant and of importance in terms of industrial applications and circular economy. This concept of reversibility is most of the time associated with the possibility of processing at high temperatures (160–250 ◦ C) while maintaining elastic properties at moderate temperatures (−30 to 120 ◦ C). Some block copolymers present soft blocks with elastomeric behavior and rigid blocks that act like a thermoplastic phase This specific composition and nature will lead to phase separation, which causes remarkable elastic properties at room temperature.

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Conclusion