Morphological effects on glass transition behavior in selected immiscible blends of amorphous and semicrystalline polymers

The effects uncompatibilized immiscible polymer blend compositions on the Tg of the amorphous polymer were studied in the systems polystyrene/polypropylene (PS/PP), polystyrene/high density polyethylene (PS/PE) and polycarbonate/high density polyethylene (PC/PE). In the two similar systems of PS/PP and PS/PE, the Tg of PS increased with decreasing PS percentage in the blends. This variation in glass transition is attributed to the polymer domain interactions resulting from the different morphologies of various blend compositions. Experiments were conducted to study these effects by preparing blends with various polymers that varied the relationship between the Tg of the amorphous polymer and the crystallization behavior of the semicrystalline polymer. Results show that the variation in amorphous component Tg with composition depends strongly on the physical state of the semicrystalline domains. Whereas the Tg of PS in PS/PE blends changed with composition, the Tg of PC in the PC/PE blend did not change with composition.