Morphology and mechanical properties of styrene‐butadiene‐styrene/polystyrene semi‐interpenetrating polymer networks and their blends

Abstract

Abstract SBS/PS semi‐interpenetrating polymer networks (semi‐IPNS) were synthesized by swelling a linear styrene‐butadiene‐styrene (SBS) triblock copolymer (SBS, Kraton 1102) with styrene monomer plus benzoin as photoinitiator and divinylbenzene as cross‐linking agent. Polyblends were prepared by solution casting of SBS and polystyrene (PS) in their ideal solvents. Measurements were made for viscoelastic properties and mechanical properties of phase‐separated polymer alloy (including SBS copolymers Kraton 4122), semi‐IPNs and polyblends of several SBS and PS, with the same total PS content (48% PS). The dynamic mechanical behaviour shows distinct transitions for each polymer, in agreement with electron microscopy results that SBS/PS polymer alloy forms two phases; however, the phase domains were finer in the semi‐IPNs than in SBS triblock copolymer and in polyblends of the corresponding polymers. Stress‐strain data show that semi‐IPNs exhibit higher tensile strength and modulus than the other two corresponding polymer alloys. A master curve was plotted to illustrate the stress relaxation behaviour of samples at higher temperatures. Our results also reveal that semi‐IPNs have much better high‐temperature mechanical strength.