Compatibilized Polypropylene Hybrid Composites: Influence of Elastomeric Interlayers on Mechanical Properties and Nucleation Behaviour

Two families of polypropylene hybrid composites were prepared by simultaneously compounding polypropylene at 240°C together with SEBS thermoplastic elastomers and filler particles, for example, anisotropic talc and isotropic glass beads. Addition of SEBS was compared with that of maleic-anhydride-grafted SEBS (SEBS-g-MA) to study the role of SEBS compatibility with fillers, especially formation of elastomeric interlayers, on mechanical properties, morphology and nucleation behaviour. At a constant filler volume fraction of 10 vol.%, SEBS and SEBS-g-MA addition were varied between 0 and 20 vol.%. Due to coupling of amino groups at the glass-bead surface with succinic anhydride side chains of SEBS-g-MA, filler particles were encapsulated in a SEBS shell. The improved interfacial adhesion of SEBS-g-MA with respect to SEBS was reflected by higher yield stresses of the compatibilized hybrid composites. Such interlayers were detected by means of transmission electron microscopic imaging of thin sections of talc-based hybrid composites. Investigation of crystallization by means of polarized light microscopy revealed that elastomeric interlayer formation via in situ filler encapsulation markedly reduced filler-induced nucleation of polypropylene crystallization.