Abstract
We show that the density and temperature dependences of the α-relaxation time of several glass-forming polymers can be described through a single scaling variable X = e(ρ)/T, where e(ρ) is well fitted by a power law ρx, x being a species-specific parameter. This implies that "fragility" is an intrinsic, density-independent property of a glass-former characterizing its super-Arrhenius slowing-down of relaxations, and it leads us to propose a modification of the celebrated Angell plot.