Effect of casting solvents on certain physical properties of ABA poly(styrene-b-butadiene) copolymers

The effects of casting solvent and, to a limited extent, solvent evaporation rate have been investigated for ABA poly(styrene-b-butadiene) copolymers. The solvents investigated were cyclohexane, CCl₄, toluene, ethyl acetate, tetralin and cyclohexanone which cover a range of solvent qualities for the respective blocks of this copolymer. The properties measured were density, sonic velocity and absorption of a swelling agent (2,2,4-trimethylpentane) plus dynamic and thermomechanical measurements. The latter techniques indicated that as well as the glass transitions of the blocks, there was a shoulder at around 50°C. It was thought likely that the origin of this minor transition was a mixed phase. It was found that the properties of sheet cast from toluene were dependent on evaporation rate, but that there was no evaporation rate dependence when the casting solvent was cyclohexane.