| Abstract: | Tensile properties of poly(butadiene-g-α-methyl styrene) copolymers have been investigated on molded samples. These graft copolymers show thermoplastic elastomer behavior because of their graft copolymer structure. Both modulus and strength increase with increasing α-methyl styrene content and tensile strength is highest at the 45–50% by weight α-methyl styrene level. Tensile strength at elevated test temperatures is considerably higher for these poly(butadiene-g-α-methyl styrene) copolymers than for styrene-butadiene-styrene triblock polymers. This is attributed to the higher glass transition temperature for poly(α-methyl styrene) segments compared to polystyrene segments. The oil acceptance of these graft copolymers appears to depend on the number of loose polybutadiene chain ends. Thus, the tensile strength of oil-extended poly(butadiene-g-α-methyl styrene) copolymers was considerably lower than oil-extended poly(styrene-b-butadiene-g-α-methyl styrene) copolymers even though both copolymers contained equal hard segment contents. |
