Use of ZIF-8 as vulcanization additive to optimize natural rubber composites to lower the amount of ZnO

Zinc oxide (ZnO) is widely used as an activator in the vulcanization process of natural rubber. However, due to its poor compatibility with natural rubber, a large amount of ZnO needs to use, and the unreacted ZnO can precipitate in various ways, posing significant harm to aquatic organisms and microorganisms. Therefore, it is necessary to reduce the dosage of ZnO in order to minimize its environmental impact. In this study, we applied ZIF-8, a zinc-based metal–organic framework, as a vulcanization additive in natural rubber. and it was found that ZIF-8 could promote the rubber vulcanization reaction by adsorbing sulfur, promoting sulfur ring-opening, and providing different ligand interactions of Zn²⁺. Moreover, even at low usage levels of ZIF-8, it effectively reduces the amount of ZnO while simultaneously improving the mechanical properties of the samples. This work provides an effective method to reduce the amount of ZnO without sacrificing the rubber properties and provides a new idea for the application of ZIF-8 in rubber materials.

Highlights

• ZIF-8 enhances properties of natural rubber composites with low ZnO dosages.
• Revealing the reason why ZIF-8 promotes the vulcanization of natural rubber.
• Investigation of the effect of ZIF-8 on the vulcanization properties of natural rubber.