SBS is a triblock copolymer of styrene, butadiene and styrene in which two glassy polystyrene end blocks are joined by a rubbery polybutadiene middle block [1]. Below the glass transition of polystyrene the end blocks aggregate into domains that act as physical crosslinks, so the material behaves as a vulcanised rubber yet flows when heated above about 100 degrees Celsius [1]. The polybutadiene block carries a double bond in every repeat unit, and that unsaturation is the point of sulfur vulcanisation, of hydrogenation and of graft polymerisation [2]. The same segment oxidises in air and the material yellows as conjugated carbonyl groups accumulate [3]. Commercial grades differ in styrene-to-butadiene ratio and in block molecular weight, and those two variables fix modulus, hardness and melt viscosity [1].
- triblock copolymer
- thermoplastic elastomer
- polystyrene domain
- polybutadiene midblock
- physical crosslink
References
- HATAKEYAMA, J.; FUJIMURA, H.; MITSUHASHI, Y.; OHTAKE, Y.; FURUKAWA, M.; Discoloration Mechanism of Thermoplastic Elastomer "Styrene-Butadiene-Styrene Block Copolymer" Products. NIPPON GOMU KYOKAISHI 2005, 78, 413-418, 10.2324/gomu.78.413.
- Wu, G.; Zeng, S.; Ou, E.; Yu, P.; Lu, Y.; Xu, W.; Photoinitiator grafted styrene–butadiene–styrene triblock copolymer. Materials Science and Engineering: C 2010, 30, 1030-1037, 10.1016/j.msec.2010.05.004.
- Fong, H.; Reneker, D.H.; Elastomeric nanofibers of styrene-butadiene-styrene triblock copolymer. Journal of Polymer Science Part B: Polymer Physics 1999, 37, 3488-3493, 10.1002/(sici)1099-0488(19991215)37:24<3488::aid-polb9>3.0.co;2-m.