Mechanism for Cross-Linking Polychloroprene With Ethylene Thiourea and Zinc Oxide

Abstract

An investigation into the mechanism by which ethylene thiourea (ETU) cross-links polychloroprene in combination with zinc oxide (ZnO) was undertaken. This was achieved through an examination of the mechanisms of cross-linking polychloroprene rubber (CR) with ETU and ZnO separately and in unison. Spectroscopic and physical characterisation techniques were employed to probe the cross-linking mechanisms of CR using other standard rubber accelerators and model compounds with analogous structures and functionalities to ETU. These investigations have resulted in the proposal of a new mechanism by which ETU and ZnO can synergistically cross-link polychloroprene, in addition to providing new evidence to support concomitant mechanisms already published for cross-linking polychloroprene.

Effect of norbornyl modified soybean oil on CB‐filled chloroprene rubber

“…However, to achieve a better performance and a faster curing of CR compounds, ethylene thiourea (ETU) is widely used. The curing mechanism of CR compounds were studied by many researchers . It is generally accepted that the major curing site of CR is the tertiary allylic chlorine atom.…”

Doping of Chlorine from a Neoprene Adhesive Enhances Degradation Efficiency of Dyes by Structured TiO2-Coated Photocatalytic Fabrics

“…In the crosslinking process, the C=C double bond on the polarity of chlorine can react with a crosslinking agent ZnO. The chlorine replaces the lattice oxygen of ZnO [29].…”

CR composites with improved processing safety crosslinked via Heck's reaction

“…Due to the electronegative chlorine atom, vulcanization of chloroprene rubber (CR) differs from that of other diene polymers 9–12 . Presence of chlorine atoms in CR macromolecules decreases the reactivity of double bonds, and thereby the common sulfur curing system results in the slow and/or ineffective vulcanization 10,11 .…”

“…Presence of chlorine atoms in CR macromolecules decreases the reactivity of double bonds, and thereby the common sulfur curing system results in the slow and/or ineffective vulcanization 10,11 . Therefore, the typical crosslinking system for CR consists of 4 phr of MgO and 5 phr of ZnO, mostly in the presence of ethylene thiourea (ETU) 9,10,13,14 . Although many published works refer to different crosslinking systems for CR, metal oxides are still particularly favorable, due to the good processability of rubber compounds and superior mechanical properties of vulcanizates 9,10,14 …”