Some molten metals have the same viscosity as water at room temperature. Casting and welding, two liquid metal-based manufacturing methods that need the molten metal to fill the mold cavity or weld seam before hardening, require low viscosity. Lubricants and coolants are used in a variety of applications, including metal forming and machining, and their viscosity has an impact on their performance.
Glass-ceramics progressively transition from solid to liquid states as the temperature rises; unlike pure metals, they do not melt immediately. At room temperature, glass is solid and brittle, with no inclination to flow; its viscosity is infinite for all practical purposes. When heated, glass softens, becoming less viscous (more fluid) and able to be blown or molded at about 1100°C (2000°F).
The bulk of polymer shaping techniques are employed at high temperatures when the material is either liquid or highly pliable. The most basic and obvious example is thermoplastic polymers, which are also the most common polymers. At low temperatures, thermoplastic polymers are solid; as the temperature rises, they transform into a soft rubbery material, followed by a thick fluid. The viscosity of polyethylene, the most commonly used thermoplastic polymer, decreases as temperature rises. Other variables, on the other hand, complicate polymer interaction. The pace of flow, for example, influences viscosity. The viscosity of a thermoplastic polymer varies.
A polymer melt’s behavior is not Newtonian. Depicts the connection between shear stress and shear rate. As the shear rate increases, the viscosity of pseudoplastic fluids falls. This characteristic complicates the analysis of polymer shape.