heatsoftened

Heatsoftened, often written heat-softened, describes a material whose mechanical properties become softer as a result of heating. In this state the material can deform, flow, or be shaped under modest forces. The term is used across fields such as polymers, waxes, glass, ceramics, and metals, though the specifics vary by material.

In polymers the effect arises from thermal transitions. As temperature approaches Tg or Tm, molecular mobility increases and stiffness decreases. Below Tg polymers are hard; above Tg they soften; near Tm crystals melt, enabling flow. The softening point is a defined temperature where a material becomes pliable under a test load, while Tg describes softened behavior in amorphous polymers.

In manufacturing heatsoftening enables shaping. Thermoforming, hot pressing, or bending use heat to bring a sheet or part into a pliable state, after which it is formed and cooled to set the final shape. Annealing of glass and metals involves heating to a chosen temperature to reduce internal stresses and increase ductility, with controlled cooling to retain softness or prevent crystallization.

Measurement and limits: Techniques such as differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) identify Tg and softening ranges. Viscosity, hardness, and indentation tests also characterize softening. The softening behavior is often time- and rate-dependent; prolonged heating can lead to degradation in polymers or oxidation in metals.

Related concepts include the glass transition temperature, softening point, melting, viscosity, and annealing. The term emphasizes that heating reduces rigidity, enabling deformation or flow.