Meltability

Meltability refers to the ease with which a solid substance can be transformed into a liquid by heating. It encompasses the temperature range over which melting occurs, typically characterized by a melting point for pure crystalline substances or by a melting range for impure or polymeric materials. In thermodynamics, melting is a solid-to-liquid phase transition driven by entropy increase and weakened lattice cohesion.

Factors influencing meltability include the strength and character of intermolecular or interatomic bonds, crystal structure, impurities, and temperature and pressure conditions. Substances with strong ionic or covalent bonds and highly ordered lattices tend to have higher melting points and lower meltability, whereas weaker van der Waals forces or disordered structures favor lower melting points. Impurities generally depress the melting point and broaden the transition. In polymers, meltability is also affected by molecular weight, tacticity, crystallinity, and the presence of plasticizers or fillers; processing aids can modify flow in the melt.

Measurement and related concepts: Meltability is commonly assessed by determining the melting point or the melting range, using differential scanning calorimetry (DSC), melting point apparatus, or hot-stage microscopy. For polymers and viscoelastic materials, melt flow properties such as melt viscosity or melt flow index are used to gauge how a melt behaves during processing.

Applications and context: The meltability of a material affects processing choices in manufacturing, such as casting, extrusion, or injection molding, and influences product performance. In foods, fats and sugars have characteristic melt behavior that affects texture and mouthfeel. In metallurgy and geology, the melting behavior of alloys and minerals governs refining, joining, and geological processes.

Related concepts include fusibility, fusion enthalpy, and eutectic systems.