*Article* **Friction, Abrasion and Crack Growth Behavior of In-Situ and Ex-Situ Silica Filled Rubber Composites**

### **Sankar Raman Vaikuntam 1,2, Eshwaran Subramani Bhagavatheswaran 1,2, Fei Xiang 1,2, Sven Wießner 1,2, Gert Heinrich 1,2, Amit Das 1,3 and Klaus Werner Stöckelhuber 1,\***


**\*** Correspondence: stoeckelhuber@ipfdd.de; Tel.: +49-351-4658-579

Received: 4 November 2019; Accepted: 23 December 2019; Published: 7 January 2020

**Abstract:** The article focuses on comparing the friction, abrasion, and crack growth behavior of two di fferent kinds of silica-filled tire tread compounds loaded with (a) in-situ generated alkoxide silica and (b) commercial precipitated silica-filled compounds. The rubber matrix consists of solution styrene butadiene rubber polymers (SSBR). The in-situ generated particles are entirely di fferent in filler morphology, i.e., in terms of size and physical structure, when compared to the precipitated silica. However, both types of the silicas were identified as amorphous in nature. Influence of filler morphology and surface modification of silica on the end performances of the rubbers like dynamic friction, abrasion index, and fatigue crack propagation were investigated. Compared to precipitated silica composites, in-situ derived silica composites o ffer better abrasion behavior and improved crack propagation with and without admixture of silane coupling agents. Silane modification, particle morphology, and crosslink density were identified as further vital parameters influencing the investigated rubber properties.

**Keywords:** elastomers; in-situ silica; friction; abrasion; tear fatigue test
