Room‑temperature Poisson's ratio values (dimensionless) for typical engineering polymers are summarized below. For most plastics, Poisson's ratio ranges from 0.30 (stiff thermosets) to about 0.46 (soft thermoplastics). Compare these with Poisson's Ratios of Metals or explore other Material Properties.
How polymers compare to metals: most structural metals cluster around ν≈0.27–0.33, whereas common thermoplastics fall in ν≈0.33–0.46. Higher ν in polymers stems from molecular chain mobility and viscoelastic deformation. Fillers (glass/carbon fiber), crystallinity, orientation, and temperature can shift ν downward (stiff fillers, lower temperature) or upward (near Tg).
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