Pure density

True density is an important term in materials science and refers to the density of a material that takes into account only its pure constituents. In contrast, bulk density measures the overall density of a material including all cavities and porosities. Particularly in the case of solid injection-moulded parts, i.e. plastic parts that are not foamed, true density and bulk density are identical.

This means that the density of the plastic part is based solely on its solid material, without taking into account cavities or other inclusions. This equality between true density and bulk density is crucial, as it indicates a homogeneous material structure that is free of cavities or inclusions. True density therefore serves as an important characteristic value for the quality and consistency of injection-moulded plastic parts.