Zinc Oxide in Rubber Compounding

zinc oxide in rubber compounding


Zinc oxide in rubber compounding acts as an activator in the formulation. It vulcanizates the rubber properties, improves efficiency and reduces the vulcanization time. 



Zinc oxide in rubber compounding


The rubber industries contribute significantly to a nation’s economy. Therefore, improvement in the rubber quality can make significant growth in the industry. 


It is used as an activator in the process, it becomes a popular ingredient for completing rubber vulcanization using sulfur.


Moreover, using zinc oxide brings other benefits, such as: 

  • Improved heat resistance
  • Enhances abrasion resistance 
  • Reduction in the build-up of heat. 



High thermal conductivity of zinc oxide in rubber compounding 


Zinc oxide has high thermal conductivity, which helps to dissipate the local heat concentrations in the rubber. Besides vulcanization of rubbers, the ingredient, zinc oxide also helps in processing uncured or untouched rubbers. 


For instance, it is mixed in rubber formulations to reduce the shrinking capacity of molded rubbers. Moreover, the excellent ingredient also maintains the cleanliness of the rubber molds (products). 



Its role in rubber compounding – The benefits in its formulation 


There are several reasons why it is an essential factor in rubber formulations. Here are a few of them to shed light on the importance of zinc oxide in the rubber industry:



Activates the entire curing system 


Stearic acid and zinc oxide can be added together to form zinc soap. This combination improves zinc oxide’s solubility in the rubber compound. 


The accelerator formula forms a complex element that reacts with sulfur to produce a strong yet working vulcanizing agent for the rubber compounds. 



Improves the cross-linking density of the rubber compounds 


Zinc oxide, together with stearic acid forms a type of salt, which is mixed or chelated with a rubber accelerator. Note that the accelerator contains sulfur and is from the side-chaining group. 


This strengthens the weak bond and takes it to a stable state by cracking and changing the position of the sulfur bonds. Therefore, rubber vulcanization produces short cross-linking. You can add new cross-linking keys in the rubber compound to increase the density. 



Improves the anti-aging properties of vulcanized rubber 


The polysulfide bond break in the process of rubber vulcanization. The results will produce H2S, which will accelerate the rubber cracking. However, zinc oxide in rubber compounding reacts with H2S to form new cross-linking bonds. 


Therefore, the use of zinc oxide stabilizes the vulcanization network and improves the anti-aging properties of the rubber. 





Zinc oxide and its properties modify the process of rubber formulation by retaining the physical properties of the compound. It is one of the best activators in the rubber industry and its function is to influence and alter the vulcanization rate of the rubber compound. 


However, researchers are figuring out a way to lower the level of zinc oxide in the formulation process as the toxicity level is harmful to aquatic organisms.



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