A restorative material which has a high proportional limit, compared with one with a lower proportional limit would have:
Proportional limit—Magnitude of elastic stress above which plastic deformation occurs.
A restorative material which has a high proportional limit, compared with one with a lower proportional limit would have more resistance to permanent deformation.
Reference: PHILLIPS’ SCIENCE OF DENTAL MATERIALS, 12th ed page no 48
Greater ductility
Greater toughness
A higher modulus of elasticity
More resistance to permanent deformation