Permeation
Permeation refers to the transport of substances through solid materials at the molecular level. This process is of great importance, as it influences the properties of materials in various applications.
The three phases of permeation
The process of permeation can be divided into three essential phases:
- Adsorption: In this first phase, gases, vapours or chemicals dissolved in liquids or suspended substances are absorbed on the surface of the plastic material. This means that the molecules of the substance enter into an interaction with the surface of the material and remain attached there.
- Diffusion: After the molecules have been adsorbed, diffusion begins. In this process, the adsorbed molecules move through the material at the molecular level. This process occurs due to concentration gradients, in which the molecules migrate from the region of higher concentration to the region of lower concentration. The speed and efficiency of this diffusion depend on the nature of the material and the properties of the diffusing substances.
- Desorption: In the final phase, the diffused molecules escape as gas on the opposite side of the material. This means that the substances leave the material and pass into the surrounding atmosphere or into an adjacent medium.
High permeation resistance
A central aim of polymer engineering is to develop high-performance plastics that exhibit the lowest possible permeation. A high permeation resistance means that the material strongly restricts the passage of substances. Materials with a low degree of permeation are particularly important in medical technology, chemical apparatus engineering and food technology. Here they can help to improve the safety and efficiency of products and processes. Fluoroplastics are an example of materials with a particularly high permeation resistance and are therefore frequently used in applications where low substance transmission is required.
Inertness and permeation
In addition to permeation, the chemical inertness of a material is also a decisive factor for its suitability in permanent contact with liquids. Inertness means that the material does not react with the chemicals contained in them and thus its structural integrity and the purity of the liquids remain guaranteed. This is particularly important in areas such as medical technology, where materials are often in contact with sensitive liquids over long periods of time and must not cause any contamination.