Meaning
Short polymer chains with a molecular mass below one thousand daltons are small enough to migrate through plastic and potentially enter food or the environment. These sub-1000 da polyolefin oligomers represent the fraction of the polymer most likely to be mobile. Their presence is a result of incomplete polymerization or thermal degradation during processing.
Reducing the concentration of these chains is a goal for manufacturers of high purity resins.
Size Limit
The molecular weight cut-off is based on the ability of the substance to pass through biological membranes. Because sub-1000 da polyolefin oligomers fall below this threshold, they are of particular interest to toxicologists.
Migration Pathway
Molecules move through the amorphous regions of the polymer by a process of diffusion. In sub-1000 da polyolefin oligomers, the small size of the chains allows them to pass through the spaces between the larger polymer molecules. This movement is accelerated by heat, making the risk higher during the moulding process or when the part is used for hot-filling.
The rate of migration depends on the concentration of the oligomers and the density of the plastic. High-density materials generally exhibit lower migration rates than low-density ones.
Exposure Potential
Evaluating the total quantity of these small molecules is a requirement for many food safety regulations. Findings regarding sub-1000 da polyolefin oligomers help resin producers improve their catalysts and processing conditions. Reducing the level of these mobile chains enhances the safety and quality of the final moulded product.
