Nano-mechanical imaging reveals heterogeneous cross-link distribution in sulfur-vulcanized butadiene-styrene rubber comprising ZnO particles. (19th December 2016)

• Record Type: Journal Article
• Authors: Glebova, Yulia; Reiter-Scherer, Valentin; Suvanto, Sari; Korpela, Tarmo; Pakkanen, Tuula T.; Severin, Nikolai; Shershnev, Vladimir; Rabe, Jürgen P.
• Is Part Of: Polymer. Volume 107(2016)
• Page Start: 102
• Page End: 107
• Publication Date: 2016-12-19
• Subjects: Rubber cross-link distribution -- Zinc oxide -- Scanning force microscopy -- Nano-mechanical imaging -- Force-distance curves -- Sulfur vulcanization; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2016.11.011
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: The addition of zinc oxide (ZnO) to sulfur (S-) vulcanized rubbers is known to accelerate the cross-linking kinetics and to increase the heterogeneity of the cross-link density. However, the spatial distribution of cross-links is hardly known and the mechanism of the activity of ZnO is disputed. We therefore investigated S-vulcanized butadiene-styrene rubber comprising ZnO particles. The samples were fractured and then investigated employing the nano-mechanical mapping mode (NM) of scanning force microscopy (SFM), supported by scanning electron microscopy (SEM). We find that rubber around the ZnO particles exhibits a higher Young's modulus in a shell with a width up to about 200 nm. Furthermore, the extension and retraction curves on these shells exhibit a smaller hysteresis than on the rubber further away from the ZnO particles. We attribute the higher Young's modulus and the smaller hysteresis to a higher cross-link density in rubber surrounding the ZnO particles and we discuss a mechanism of the activity of ZnO in rubbers which can explain this. Graphical abstract: Highlights: Nano-mechanical imaging of sulfur-vulcanized butadiene-styrene rubber comprising ZnO particles is performed. It reveals a shell of rubber around ZnO particles with higher Young's moduli, lower pull-off forces and smaller hysteresis. The shell is attributed to a higher rubber cross-link density and explained with the activity of the ZnO particles.