Melt blending of polystyrene/hyperbranched polyester and styrene-maleic-anhydride/hyperbranched polyester: An investigation into generation and processing technique effects

Recent work has demonstrated the effectiveness of hyperbranched polymers as processing aids for polyolefins and processing aids and toughening agents for thermosetting resins. The effectiveness of hyperbranched polymers in polymer blending schemes stems from their globular molecular structure and high density of reactive functional groups. In this investigation, the incorporation of hyperbranched polyols (HBP) into polystyrene based thermoplastic matrices was studied. One volume fraction of several generations, or molecular weights, of HBP were melt blended with non-reactive polystyrene and reactive styrene-maleic anhydride (SMA). Processing data proved that all generations of HBPs are effective processing aids for both non-reactive and reactive systems. Processing torque decreased by over forty percent with the addition of HBP for both the PS and SMA based blends. Previous difficulties with processing generation 2 HBP were overcome by using high energy mixing. Thermal analysis and microscopy studies proved that the non-reactive systems formed immiscible blends while the reactive systems formed compatibilized blends. This is evidence that HBPs can be used to form compatibilizers during processing. These studies also proved that HBP generation did not affect morphological development but processing variables did.