svällningsfaktor

Svällningsfaktor, literally “swelling factor” in Swedish, is a dimensionless quantity that describes how much a material increases in volume when it is exposed to a liquid or atmosphere. The term is commonly used in the packaging, pharmaceutical, and food industries to assess the performance of absorbent materials such as ready‑to‑eat products, gel‑packs, or absorbent cores in diapers. It is also applied to polymers, foams, and other porous solids that undergo dimensional changes during drying or rehydration.

The swelling factor (S) is calculated by measuring the mass or volume of a dry sample, adding a known amount of liquid, and measuring the resulting mass or volume after equilibration. A typical formula is S = (m_f – m_d) / m_d, where m_d is the dry mass and m_f is the fully swollen mass. For volume measurements the equation becomes S = (V_f – V_d) / V_d. The value is expressed as a fraction or a percentage; a swelling factor of 1.5 means the material has become 50 % larger in the measured dimension.

Because swelled mass or volume is indicative of water or solvent uptake, the swelling factor is an important design parameter. In pharmaceuticals, it helps to predict how quickly a tablet will dissolve. In the food sector it informs shelf‑life estimation by indicating how much a product will expand when chilled or warmed. In absorbent products, a high swelling factor can improve activeness but must be balanced against material integrity and cost.

Regulatory agencies occasionally reference acceptable swelling factors in safety and quality guidelines, while manufacturers often use the metric in internal quality control programs. The measurement is straightforward, but specialists emphasize the need for standardized test conditions – such as temperature, pressure, and liquid composition – so that results are comparable across batches and laboratories.