According to the principle of thermal insulation, thermal insulation materials are divided into: ① porous materials, which are insulated by gases with low thermal conductivity filled in pores. Generally, air is used as thermal resistance medium, mainly fiber aggregation structure and porous structure materials. The smaller the fiber diameter, the smaller the bulk density of the material and the better the thermal insulation performance. The thermal conductivity of closed-cell structure is lower than that of open-cell structure. For example, when the closed-cell structure is filled with other gases with smaller thermal conductivity, the thermal conductivity of the two structures is quite different. The thermal insulation of foamed plastics is better, followed by mineral fiber, expanded perlite, porous concrete and foamed glass. (2) Reflective materials, such as aluminum foil, can greatly reduce radiation heat transfer through thermal reflection, and several layers of aluminum foil or paper can form a composite structure with thin air layer, which can also increase thermal resistance. Thermal insulation materials are divided into: fibrous aggregation tissues (inorganic or organic fibers and products); Loose granular, flaky or powdery tissues (such as lightweight aggregate, pumice and diatomite); Porous structure (porous concrete, foamed plastics, etc.). ) and dense structure (aluminum foil, etc. ). Thermal insulation materials can also be based on raw materials, density, hardness, thermal conductivity and ...
Because air is a thermal resistance, general thermal insulation materials are mainly loose and porous. So they are all light.