Zinc-Based Curing Activators: New Trends for Reducing Zinc Content in Rubber Vulcanization Process
The efficiency of sulfur vulcanization reaction in rubber industry is generally improved thanks to the combined use of accelerators (as sulphenamides), activators (inorganic oxides), and co-activators (fatty acids). The interaction among these species is responsible for the formation of intermediate...
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doaj-7630b7af4240413cb2078f0a30300e652020-11-24T22:15:15ZengMDPI AGCatalysts2073-43442019-08-019866410.3390/catal9080664catal9080664Zinc-Based Curing Activators: New Trends for Reducing Zinc Content in Rubber Vulcanization ProcessSilvia Mostoni0Paola Milana1Barbara Di Credico2Massimiliano D’Arienzo3Roberto Scotti4Department of Materials Science, INSTM, University of Milano Bicocca, Via Roberto Cozzi 55, 20125 Milano, ItalyDepartment of Materials Science, INSTM, University of Milano Bicocca, Via Roberto Cozzi 55, 20125 Milano, ItalyDepartment of Materials Science, INSTM, University of Milano Bicocca, Via Roberto Cozzi 55, 20125 Milano, ItalyDepartment of Materials Science, INSTM, University of Milano Bicocca, Via Roberto Cozzi 55, 20125 Milano, ItalyDepartment of Materials Science, INSTM, University of Milano Bicocca, Via Roberto Cozzi 55, 20125 Milano, ItalyThe efficiency of sulfur vulcanization reaction in rubber industry is generally improved thanks to the combined use of accelerators (as sulphenamides), activators (inorganic oxides), and co-activators (fatty acids). The interaction among these species is responsible for the formation of intermediate metal complexes, which are able to increase the reactivity of sulfur towards the polymer and to promote the chemical cross-links between the rubber chains. The high number of species and reactions that are involved contemporarily in the process hinders the complete understanding of its mechanism despite the long history of vulcanization. In this process, ZnO is considered to be the most efficient and major employed activator and zinc-based complexes that formed during the first steps of the reaction are recognized to play a main role in determining both the kinetic and the nature of the cross-linked products. However, the low affinity of ZnO towards the rubber entails its high consumption (3−5 parts per hundred, phr) to achieve a good distribution in the matrix, leading to a possible zinc leaching in the environment during the life cycle of rubber products (i.e., tires). Thanks to the recent recognition of ZnO ecotoxicity, especially towards the aquatic environment, these aspects gain a critical importance in view of the urgent need to reduce or possibly substitute the ZnO employed in rubber vulcanization. In this review, the reactivity of ZnO as curing activator and its role in the vulcanization mechanism are highlighted and deeply discussed. A complete overview of the recent strategies that have been proposed in the literature to improve the vulcanization efficiency by reducing the amount of zinc that is used in the process is also reported.https://www.mdpi.com/2073-4344/9/8/664zinc oxidevulcanizationactivatorzinc complexesrubberreinforcing filler |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Silvia Mostoni Paola Milana Barbara Di Credico Massimiliano D’Arienzo Roberto Scotti |
spellingShingle |
Silvia Mostoni Paola Milana Barbara Di Credico Massimiliano D’Arienzo Roberto Scotti Zinc-Based Curing Activators: New Trends for Reducing Zinc Content in Rubber Vulcanization Process Catalysts zinc oxide vulcanization activator zinc complexes rubber reinforcing filler |
author_facet |
Silvia Mostoni Paola Milana Barbara Di Credico Massimiliano D’Arienzo Roberto Scotti |
author_sort |
Silvia Mostoni |
title |
Zinc-Based Curing Activators: New Trends for Reducing Zinc Content in Rubber Vulcanization Process |
title_short |
Zinc-Based Curing Activators: New Trends for Reducing Zinc Content in Rubber Vulcanization Process |
title_full |
Zinc-Based Curing Activators: New Trends for Reducing Zinc Content in Rubber Vulcanization Process |
title_fullStr |
Zinc-Based Curing Activators: New Trends for Reducing Zinc Content in Rubber Vulcanization Process |
title_full_unstemmed |
Zinc-Based Curing Activators: New Trends for Reducing Zinc Content in Rubber Vulcanization Process |
title_sort |
zinc-based curing activators: new trends for reducing zinc content in rubber vulcanization process |
publisher |
MDPI AG |
series |
Catalysts |
issn |
2073-4344 |
publishDate |
2019-08-01 |
description |
The efficiency of sulfur vulcanization reaction in rubber industry is generally improved thanks to the combined use of accelerators (as sulphenamides), activators (inorganic oxides), and co-activators (fatty acids). The interaction among these species is responsible for the formation of intermediate metal complexes, which are able to increase the reactivity of sulfur towards the polymer and to promote the chemical cross-links between the rubber chains. The high number of species and reactions that are involved contemporarily in the process hinders the complete understanding of its mechanism despite the long history of vulcanization. In this process, ZnO is considered to be the most efficient and major employed activator and zinc-based complexes that formed during the first steps of the reaction are recognized to play a main role in determining both the kinetic and the nature of the cross-linked products. However, the low affinity of ZnO towards the rubber entails its high consumption (3−5 parts per hundred, phr) to achieve a good distribution in the matrix, leading to a possible zinc leaching in the environment during the life cycle of rubber products (i.e., tires). Thanks to the recent recognition of ZnO ecotoxicity, especially towards the aquatic environment, these aspects gain a critical importance in view of the urgent need to reduce or possibly substitute the ZnO employed in rubber vulcanization. In this review, the reactivity of ZnO as curing activator and its role in the vulcanization mechanism are highlighted and deeply discussed. A complete overview of the recent strategies that have been proposed in the literature to improve the vulcanization efficiency by reducing the amount of zinc that is used in the process is also reported. |
topic |
zinc oxide vulcanization activator zinc complexes rubber reinforcing filler |
url |
https://www.mdpi.com/2073-4344/9/8/664 |
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