lowheatconductivity

Low heat conductivity refers to the property of a material to conduct heat poorly. The measure is given by the thermal conductivity, k, expressed in watts per meter-kelvin (W/m·K). Materials with low k values are used for insulation because they slow heat transfer by conduction, convection, and, in some cases, radiation.

Low conductivity is achieved through high porosity, low density, abundant voids, small pore sizes that scatter phonons, and, in some cases, near-vacuum gaps that suppress gas conduction and radiative transfer. In solids, phonon scattering at interfaces and defects reduces conductivity; in porous materials, trapped air or gas is a poor conductor. Temperature can affect k, especially for materials where radiative transfer becomes more relevant at higher temperatures.

Common low-thermal-conductivity materials include aerogels, foamed polymers like polyurethane and polystyrene, mineral wool, fiberglass, and vacuum insulated panels. Advanced examples are silica or carbon aerogels and multilayer insulation that reduces radiative transfer with reflective foils. Some materials achieve low k by structure rather than composition, such as aerogels with nanostructured networks.

Applications include building insulation, refrigeration and cold-chain packaging, spacecraft and aerospace thermal protection, propellant tanks, and industrial equipment where minimizing heat gain or loss is essential.

Thermal conductivity is measured using methods such as the guarded hot plate or heat-flow meter methods, under defined temperatures and humidity. Standards include ASTM C177, ASTM C518, ISO 8302. For research, thermal diffusivity is measured by laser flash analysis and combined with density to derive k.

See also: thermal insulation, thermal conductivity, materials science, heat transfer.