Permeability and Plastics<\/p>\n
Permeability is the quality or property of a substance or material that allows another substance to pass through it. The substance that passes through a material\u00a0can be referred\u00a0to as the penetrating substance. Permeability can also be described as the flux of the penetrating substance through the matrix formed by the molecular structure of the material it is passing through. In polymer plastics, the main penetrating substances of interest are typically liquids, such as water or other chemicals; and gases, such as air, oxygen, methane, and so forth.<\/p>\n
Permeation \u2013 the process of the liquid or gas penetrating another material \u2013 is driven primarily by diffusion based upon the concentration and pressure gradient of the liquid or gas, the permeable material\u2019s intrinsic permeability, and the permeating liquid\u2019s or gas\u2019 ability to diffuse or spread out in another medium. Permeation is also affected by chemical reactions that occur between the penetrating substance and the material it is passing through. Chemical reactions notwithstanding, with respect to a material\u2019s permeability, the greater the concentration of a gas or liquid and the greater its pressure, the greater its ability to penetrate a material.<\/p>\n
Permeability is an important consideration for plastics because plastics are frequently used as containers, tubing, or other packaging to keep the contained items and liquids free from contaminants. Permeability is also a concern with respect to sterility for biomedical plastics applications and high-tech analytical equipment.<\/p>\n
Because the morphology of the polymer matrix changes during processing, permeation is best tested on the final product. We recommend that you are thoroughly familiar with the potential chemical exposures that your polymer products may be subjected to.<\/p>\n