BROMINATED ISOBUTYLENE-CO-PARAMETHYLSTYRENE WITH SUPERIOR IMPERMEABILITY FOR TIRE INNERLINER APPLICATIONS

Sunny Jacob; Ray Chen; Sujith Nair; Jeff Valentage

doi:10.5254/rct.21.80998

Article Contents

ABSTRACT
INTRODUCTION
EXPERIMENTAL
RESULTS AND DISCUSSION
CONCLUSIONS
ACKNOWLEDGEMENTS
REFERENCES

Editorial Type:

Article Category: Research Article

Online Publication Date: 10 May 2021

BROMINATED ISOBUTYLENE-CO-PARAMETHYLSTYRENE WITH SUPERIOR IMPERMEABILITY FOR TIRE INNERLINER APPLICATIONS

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Page Range: 549 – 574

DOI: 10.5254/rct.21.80998

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ABSTRACT

Isobutylene elastomers are of great commercial importance in tire applications because of their notable low gas permeability properties, owing to their efficient molecular packing. Brominated isobutylene-co-para-methylstyrene (BIMSM) elastomers are a special class of isobutylene elastomers synthesized by random cationic polymerization of isobutylene and para-methylstyrene (pMS), followed by a selective bromination of the methyl group of the pMS units. BIMSM elastomer, commercially known as Exxpro™ specialty elastomer, exhibits superior heat resistance and aging properties and is much more resistant to chemicals and ozone than butyl- or halobutyl polymers because of its fully saturated backbone structure. The permeability properties of BIMSM elastomers can be tuned by the level of pMS comonomer present in the polymer chain. The pMS comonomer increases the glass transition temperature of the copolymer, and polymers with very low gas permeability needed for demanding tire air retention applications can be produced by suitably selecting the pMS content. A single type of benzylic bromide, but with a versatile functional group, allows for precise control of vulcanization chemistry, potential for other chemical transformations to achieve other reactive groups, and grafting reactions. We present the new material developments to meet the growing market demands and requirements for low maintenance, low inflation pressure loss rate tires and tires for connected autonomous shared electric vehicles.

Fig. 1. —

(a) Schematic process flowchart for the production of IMSM-10; (b) schematic process flowchart for the production of BIMSM-10.

Scheme 1. —

Two step synthesis of BIMSM-10 and free radical bromination mechanism.

Fig. 2. —

¹H NMR spectrum of the IMSM-10 polymer.

Fig. 3. —

Carbon numbering for ¹³C NMR spectral assignments.

Fig. 4. —

(a) ¹³C NMR spectrum of the IMSM-10 polymer, 18–68 ppm region; (b) ¹³C NMR spectrum of the IMSM-10 polymer, 114–160 ppm region.

Fig. 5. —

FTIR spectrum of the IMSM-10 precursor polymer.

Fig. 6. —

GPC and dRI response of IMSM-10 and BIMSM-10 elastomers.

Fig. 7. —

¹H NMR overlay spectra of the IMSM-10 and BIMSM-10 elastomers.

Fig. 8. —

FTIR overlay spectra of the IMSM-10 and BIMSM-10 elastomers.

Fig. 9. —

Comparison of pMS content of IMSM-10 and BIMSM-10, calculated by ¹H NMR and FTIR, single point data.

Fig. 10. —

UV and dRI traces and UV/dRI ratio of BIMSM-10 elastomer.

Fig. 11. —

G′, G′′, and tan δ traces of the BIMSM-10 elastomer tested at a fixed frequency (1 Hz) and initial strain (0.05%).

Fig. 12. —

Variation of T_g as function of the pMS content in BIMSM-10 type elastomers, single point data.

Fig. 13. —

(a) Tan δ traces of BIIR and BIMSM-10 elastomer tested at 100 °C and 14% strain, single point data; (b) tan δ traces of BIIR and BIMSM-10 elastomer tested at 100 °C and 14% strain, single point data; (c) reduced Van Gorp–Palmen plot for BIIR and BIMSM-10 elastomer tested at 100 °C and 14% strain, single point data.

Fig. 14. —

(a) Dependence of 90% cure time (t′90), 50% cure time (t′50), and scorch (ts2) on benzylic bromine content, single point data; (b) dependence of cure time t′90, t′50, and ts2 on total Br content, single; (c) dependence of MH and MH-ML on total Br content, single point data.