Meaning
Saturated hydrocarbon molecules that move through a polymer matrix because they lack an electrical charge. Non-polar alkane migrants often originate from processing aids or the base resin itself in polyolefins. These substances can accumulate on the surface of a part, creating a greasy feel or affecting adhesion.
Diffusion Mechanism
Lack of polarity allows these molecules to slip between polymer chains with minimal resistance. Temperature increases the rate at which non-polar alkane migrants reach the exterior of the moulded item. This movement is a function of molecular weight, where smaller chains move faster than larger ones.
Surface Interaction
Once on the surface, these alkanes can interfere with printing, painting or secondary bonding processes. Non-polar alkane migrants act as a release agent that prevents adhesives from wetting the plastic. Cleaning the parts with solvents provides only a temporary fix as more material migrates from the core.
Regulatory Compliance
Limits are placed on these substances in medical and food packaging to prevent contamination. Analytical labs measure the concentration of non-polar alkane migrants using hexane extraction. High levels may indicate a problem with the resin purity or the additive package.
Maintaining low levels of these migrants is essential for parts intended for medical assembly.
