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Effect of rubber reinforcement with filler on extrusion flow and extrudate swell

Hidenori Hirai, Hideyuki Uematsu, Yuji Sato and Shuichi Tanoue


The extrusion process of silica rubber through a chemical reaction is unstable, and the flow mechanism in the extruder is still unclear. In this study, styrene-butadiene rubber (SBR) has been chosen as the matrix and the reinforcing effects of two different kinds of fillers, silica and titanium dioxide, have been investigated on SBR. Additionally, the effect of the properties of the SBR/filler composites on extrudate swelling has been examined. The reinforcing effect of the filler was confirmed by dynamic viscoelasticity, and the swell ratio was measured using a capillary rheometer. The results suggest that titanium dioxide has no reinforcing effect, as there is no interaction between titanium dioxide and the molecular structure of SBR. In contrast, there was a significant interaction between silica and SBR. It was found that the bound rubber, which is an SBR gel with restricted molecular chains, causes a reduction in the swell ratio, and this reduction effect is larger than that caused by filling the filler in the matrix. Furthermore, it was observed that this bound rubber deforms during flow and affects the extrudate swell phenomenon.

Corresponding author: Hidenori Hirai, Tire Production Technology Division, THE YOKOHAMA RUBBER Co., Ltd., 2-1 Oiwake, Hiratsuka City, Kanagawa Prefecture 254-8601, Japan; and Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Fukui, Japan, E-mail:

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: None declared.

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.


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Received: 2021-06-29
Accepted: 2022-02-12
Published Online: 2022-03-22
Published in Print: 2022-05-25

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