Effect of the molecular weight of poly(ethylene glycol) on the plasticization of green sheets composed of ultrafine BaTiO3 particles and poly(vinyl butyral)

The effect of the molecular weight (MW) of poly(ethylene glycol) (PEG) on the plasticization of poly(vinyl butyral) (PVB) binder in green BaTiO3 sheets prepared with PEG with MW values of 400 and 1530 was investigated. The MW of PEG had a profound effect on the rheological properties of the suspension as well as the physical properties of the green sheet. The suspension viscosity decreased with decreasing MW of PEG for shear rates above 4 s−1. PEG 400 gave rise to a higher degree of plasticization of the green sheet than PEG 1530. This was due to the reduction in hydrogen bonding between the vinyl alcohol units in the PVB binder in the green BaTiO3 sheet, as identified by FT-IR spectroscopy. As the MW of the PEG decreased, the green BaTiO3 sheets exhibited a lower glass transition temperature, and a noticeably more ductile behavior. These results indicate that the green sheets became more flexible due to a higher plasticizing effect. However, laminated green BaTiO3 sheets prepared with PEG 1530 showed delamination defects that were observed at a cut surface, which arose because of the low plasticization. This suggests that PEG 1530 has limited utilization as a plasticizer for the BaTiO3/PVB binder system.