Editorial Type:
Article Category: Research Article
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Online Publication Date: 21 Jul 2021

EFFECT OF EMULSION SBR PREPARED BY ASYMMETRIC REVERSIBLE ADDITION-FRAGMENTATION TRANSFER AGENT ON PROPERTIES OF SILICA-FILLED COMPOUNDS

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Page Range: 735 – 758
DOI: 10.5254/rct.21.79904
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ABSTRACT

The development of ultra-high-performance tires that satisfy fuel efficiency, traction, handling performance, and abrasion resistance has gained significant importance in the tire industry. Solution SBR has been used as a raw material, owing to its useful characteristics (e.g., narrow dispersity controllable microstructure and chain-end functionalization). In a recent improvement, emulsion SBR (ESBR), a high-molecular-weight compound with narrow dispersity, has been reported for application in the tire tread compounds. In particular, S,S-dibenzyl trithiocarbonate (DBTC) reversible addition-fragmentation transfer (RAFT) ESBR has exhibited excellent abrasion resistance and fuel efficiency in unfilled and carbon black–filled vulcanizates. However, owing to the symmetrical structure of DBTC RAFT ESBR, the polymer chain was shortened by the reaction of a silane coupling agent with trithiocarbonate, leading to poor abrasion resistance and fuel efficiency in the case of silica-filled vulcanizates. In this study, benzyl (4-methoxyphenyl) trithiocarbonate (BMPTC), an asymmetric RAFT agent that promotes unilateral polymer growth, was synthesized and used in the polymerization of BMPTC RAFT ESBR. Chain cleavage was not observed. Upon application to silica-filled vulcanizates, BMPTC RAFT ESBR exhibited improved abrasion resistance (by 9%), improved fuel efficiency (by 20%), and improved wet traction performance (by 10%) compared with the DBTC RAFT ESBR.

Copyright: 2021
Fig. 1.
Fig. 1.

Scheme of the RAFT polymerization. kβ, fragmentation constant of pre-equilibrium; kadd, addition constant of pre-equilibrium; kaddP, addition constant of RAFT equilibrium; kp, propagation constant; M, monomer; P, polymer chain; R, leaving group; Z, a group that regulates the activity of C=S bond.

Fig. 2.
Fig. 2.

Reaction mechanism of the symmetric RAFT ESBR with a silane coupling agent.

Fig. 3.
Fig. 3.

Scheme of the purpose of this research.

Fig. 4.
Fig. 4.

Synthesis of BMPTC.

Fig. 5.
Fig. 5.

NMR spectra of BMPTC RAFT agent (a) before purification and (b) after purification.

Fig. 6.
Fig. 6.

NMR spectra of BMPTC RAFT agent: (a) 1H-NMR and (b) 13C-NMR.

Fig. 7.
Fig. 7.

GPC curves of (i) ESBR, (ii) DBTC RAFT ESBR, and (iii) BMPTC RAFT ESBR polymers.

Fig. 8.
Fig. 8.

1H-NMR spectra of (a) ESBR, (b) DBTC RAFT ESBR, and (c) BMPTC RAFT ESBR polymers.

Fig. 9.
Fig. 9.

A suggested mechanism of the reaction between the DBTC RAFT ESBR and the silane coupling agent.

Fig. 10.
Fig. 10.

A suggested mechanism of the reaction between the BMPTC RAFT ESBR and the silane coupling agent.

Fig. 11.
Fig. 11.

GPC curves of (a) ESBR, (b) DBTC RAFT ESBR, and (c) BMPTC RAFT ESBR polymers after reaction with silane coupling agent.

Fig. 12.
Fig. 12.

1H-NMR spectra of (a) ESBR, (b) DBTC RAFT ESBR, and (c) BMPTC RAFT ESBR polymers after reaction with the silane coupling agent.

Fig. 13.
Fig. 13.

Payne effect results of ESBR, DBTC RAFT ESBR, and BMPTC RAFT ESBR SMBs.

Fig. 14.
Fig. 14.

Cure characteristics of ESBR, DBTC RAFT ESBR, and BMPTC RAFT ESBR SMBs without curatives.

Fig. 15.
Fig. 15.

Crosslink density of vulcanizates of ESBR, DBTC RAFT ESBR, and BMPTC RAFT ESBR silica-filled compounds.

Fig. 16.
Fig. 16.

Cure characteristics of ESBR, DBTC RAFT ESBR, and BMPTC RAFT ESBR silica-filled compounds with curatives.

Fig. 17.
Fig. 17.

Temperature dependence tan δ of vulcanizates of ESBR, DBTC RAFT ESBR, and BMPTC RAFT ESBR silica-filled compounds (silica 60 phr).

Fig. 18.
Fig. 18.

Mechanical properties of vulcanizates of ESBR, DBTC RAFT ESBR, and BMPTC RAFT ESBR silica-filled compounds (silica 60 phr).

Contributor Notes

*Corresponding author. Ph: +82-51-510-2461; Fax: +82-51-512-8563; email: whkim@pusan.ac.kr
Received: 01 Oct 2020
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