Densification of a polymer glass under high-pressure shear flow

The properties of glasses can change significantly as they evolve toward equilibrium. Mechanical deformation appears to influence this physical aging process in conflicting ways, with experiments and simulations showing both effects associated rejuvenation away from overaging the equilibrium state. Here we report a significant densification effect polymer undergoing shear flow under high pressure. We used high-aspect ratio geometry layer compression test measure uniform homogeneous accumulation plastic strain during isothermal confined deeply quenched film polystyrene glass. Combined scanning transmission x-ray microscopy (STXM) atomic force confirmed defect-free leaving up 1.2% residual conditions uniaxial strain. At higher peak strain, extruded glass below compressing punch background A further density increase 2% was observed by STXM for highly thinned thickness that nevertheless showed no signs crystallization or internal localization. While be accounted simple elastic--plastic constitutive model, high-pressure extrusion cannot.