Effects of plasticization and hydrostatic pressure on tensile properties of PMMA under compressed carbon dioxide and nitrogen

We investigated the stress-strain behavior of PMMA films under compressed CO2 and N-2. The elongation at break increased and the stress decreased with increasing CO2 pressure at pressures above 3 MPa, indicating that the tensile property changed from brittle to ductile under compressed CO2. In contrast, the material property became more brittle under compressed CO2 at pressures below 2 MPa and under compressed N-2. By depressurizing the compressed gas and excluding the hydrostatic pressure, the property of the gas-absorbed specimen changed from brittle to ductile. These results suggest that deformability by molecular orientation is enhanced by the plasticizing effect caused by a large amount of absorbed gas while it is suppressed by the effect of hydrostatic pressure caused by a small amount of absorbed gas. Conversely, the elastic modulus decreased under both compressed CO2 and N-2, but the decrease under CO2 was much larger than that under N-2, suggesting that distortion in the elastic region is dominated by the plasticization effect. (C) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43431.