An innovative method to reduce percolation threshold of carbon black filled immiscible polymer blends

An innovative methodology for selective localization of carbon black (CB) at the interface of immiscible polypropylene/polystyrene (PP/PS) polymer blend in order to reduce the percolation threshold in CB-filled conductive polymer composites has been investigated. In CB–PP/PS blends, CB was found to preferentially localize in the PS phase. However, upon the introduction of styrene–butadiene–styrene (SBS) tri-block copolymer, CB showed higher affinity to the polybutadiene (PBD) section of the SBS copolymer, which was selectively localized at the interface between PP and PS, within the PP phase and within the PS main particle coating PS subparticles and connecting them together. There is a 40% reduction in the percolation threshold in the (70/30) PP/PS blend upon addition of 5 vol% SBS because of the selective localization of CB in the PBD phase and the change of blend morphology. SBS was found to change the morphology of the dispersed PS phase into a rod-like structure at a critical SBS loading. Moreover, for composites with or without SBS, at a certain CB loading above the percolation threshold, the mixture exhibited a co-continuous morphology in contrast to the dispersed morphology of the (70/30) PP/PS blend without CB or at low CB loadings.