Gas barrier properties and mechanism of kaolin/styrene–butadiene rubber nanocomposites

• SEM proved that kaolin layer-like particles are finely dispersed in SBR matrix.
• Modified kaolin can significantly improve gas barrier property of SBR nanocomposite.
• The barrier model of kaolin/SBR nanocomposite was established.
• The barrier mechanism of kaolin/SBR nanocomposite was investigated.

A series of kaolin/styrene–butadiene rubber (SBR) nanocomposites were prepared by melt blending. The scanning electron microscopy images of the kaolin/SBR nanocomposites showed that the kaolin particles were disorderly and finely dispersed in the SBR matrix. The layer-like particles also had the diameters of 300 nm to 700 nm and the thicknesses of 50 nm to 150 nm. Compared with pure SBR, the kaolin/SBR nanocomposites exhibited excellent gas barrier properties, and the oxygen permeability of the kaolin/SBR nanocomposites decreased by 64% with increased kaolin content to 80 phr. The gas barrier properties of the kaolin/SBR nanocomposites were much better than those of SBR materials filled with precipitated silica or carbon black. The physical dispersion of kaolin layer-like particles had a significant effect on gas barrier property of kaolin/rubber composites. The gas barrier model of the kaolin/SBR nanocomposite was proposed based on the Nielsen model. The results showed that the overall orientation angle of the kaolin layer-like particles in the SBR matrix was approximately 30° to 45°, and which would decrease with increased kaolin content.