Figures published on the mill note: amorphous density 1.333 g/cm³, crystalline 1.455, typical 1.38–1.40. Moisture regain 0.4%. Softening 230–240°C, melting 255–265°C, decomposition about 300°C. Light resistance second only to acrylic. Dielectric constant 3.0–3.8.
Those numbers matter for heat-setting and for outdoor webbing that must keep color after UV exposure. UV-stabilized DTY is the yarn the polyester-classification note calls the preferred choice for outdoor straps.