trappedair

Trappedair is a term used in materials science and engineering to describe pockets of air that remain enclosed within a solid, liquid, or composite after manufacture or during service. These air pockets are typically disconnected from the external environment and persist due to a combination of porosity, surface tension, and processing conditions that limit air escape.

Causes of trapped air include manufacturing and processing steps such as mixing, pouring, vibration, compaction, and curing, as well as rapid cooling or sequencing that locks air into place. In porous materials, trapped air forms as voids within the pore structure. In some products, air may be intentionally entrapped to reduce density or modify insulation properties; in others, it is an unwanted defect that can compromise performance.

The presence of trapped air can influence several material properties. Thermal insulation often benefits from air voids because air has low thermal conductivity, while excessive or poorly distributed trapped air can degrade mechanical strength and reduce structural integrity. In concrete, trapped air voids can lower compressive strength and durability, whereas in foams and composites, the size, connectivity, and distribution of voids determine stiffness, damping, and acoustic behavior. Trapped air can also affect moisture transport and corrosion risk in some packages and devices.

Measurement and analysis of trappedair typically employ imaging and volumetric techniques. X-ray computed tomography and micro-CT provide three-dimensional views of void geometry, while density measurements and gas volume analyses estimate total porosity. Materials engineers seek to control trapped air through processing adjustments, degassing, vacuum or vibration methods, and the use of anti-foaming agents when appropriate.

See also porosity, air void, degassing.