Abstract
The thermal stability of oil gels formed by styrene-butadiene-styrene triblock copolymer (SBS) was improved by adding a small amount of poly(phenylene ether) (PPE), which has a higher glass transition temperature (Tg). In naphthenic oil which is a good solvent for the butadiene blocks, but a non-solvent for the styrene blocks and PPE, PPE was selectively included into styrene blocks in SBS, and induced the increase of the Tg of these blocks. The melting temperature determined by viscoelastic measurements and softening temperature of the gels were elevated by adding PPE, while no significant change was detected by adding polystyrene. The gel became opaque by adding PPE, and partially separated phases were observed by field emission scanning electron microscopy (FE-SEM). The dependence of the viscoelastic behavior on the PPE concentration can be explained by the structural change observed by FE-SEM.
Highlights
ABA triblock copolymers with two polystyrene end blocks connected by an elastic midblock are rubbery elastomers with thermo plasticity and excellent workability
While 20 wt% of Styrene-butadiene-styrene triblock copolymer (SBS) was necessary to form gels without Poly(phenylene ether) (PPE) in naphthenic oil, the mixtures with only 15 wt% of SBS was gelated in naphthenic oil by adding 5 wt% of PPE
The decrease of the transparency of the gels suggests the existence of partially immiscible phases of PPE and the styrene blocks
Summary
ABA triblock copolymers with two polystyrene end blocks connected by an elastic midblock are rubbery elastomers with thermo plasticity and excellent workability. Because asphalt is used at various temperatures including temperatures as high as 100 ̊C, the thermal stability of asphalt modified with SBS is expected to be improved by increasing Tg of the styrene blocks in added SBS. In order to make PPE included in the styrene blocks in SBS gels, the affinities among PPE, the styrene and butadiene blocks, and the affinities among the polymers and the solvent should be considered. This complexness has prevented to understand SBS oil gels modified with PPE. The rheological behaviors and thermal stabilities of the SBS gels were investigated, and the structures of the gels were discussed based on the results obtained by field emission scanning electron microscopy (FE-SEM) with the aid of the structures of SBS reported in the previous studies
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