The vulcanization of neoprene or polychloroprene rubber (CR rubber) is carried out using metal oxides (specifically MgO and ZnO, sometimes PbO) rather than sulfur compounds which are presently used with many natural and synthetic rubbers. In addition, because of various processing factors (principally scorch, this being the premature cross-linking of rubbers due to the influence of heat), the choice of accelerator is governed by different rules to other diene rubbers. Most conventionally used accelerators are problematic when CR rubbers are cured and the most important accelerant has been found to be ethylene thiourea (ETU), which, although being an excellent and proven accelerator for polychloroprene, has been classified as reprotoxic. The European rubber industry has started a research project SafeRubber to develop a safer alternative to the use of ETU.

Is it true that is a non metal used in the vulcanisation of rubber?
no