Migration of cosmetic components into plastic packaging material

Abstract

The interaction between cosmetic products and packaging materials is a critical issue in various industries, particularly in cosmetics. This study investigated key factors influencing the migration of product components into the packaging material to better understand the process. The research focused on HDPE samples, as it is widely used to manufacture cosmetic bottles from both virgin and recycled sources. To assess migration variations across different HDPE samples, other POs were included for comparison. Migration measurements determined the diffusion coefficient as a comparative parameter for different polymer materials, various migration components, and their conditions. Initially, product properties were analyzed for their migration behavior. Various components, primarily oils, displayed migration patterns influenced by polarity, molecular size, and viscosity. Smaller and more non-polar molecules demonstrated a faster migration. Further migration measurements under various environmental conditions, including those embedded in emulsions, revealed that higher temperatures and smaller emulsion droplet sizes facilitate faster oil migration. In emulsions, oil-based systems enabled faster migration compared to a water-based emulsions. The diffusion process of oils was facilitated when the oil formed the continuous phase in direct contact with the packaging wall. Other emulsion components, such as thickening emollients and emulsifiers, and their variations in the choice and concentration showed no impact on oil migration. These findings were consistent in all measured PO materials.The study also observed differences in migration behavior across different PO samples. For comparative analysis, isopropyl palmitate at 40 °C was used as a model. The diffusion coefficient and oil uptake varied across POs. PP exhibited the highest oil uptake, followed by LDPE, LLDPE, and HDPE, correlating with material density. Lower-density materials, like PP, had greater inter-chain spacing, facilitating oil migration, while virgin and recycled HDPE showed migration but exhibited no differences in oil uptake. Conversely, migration speed, defined by the diffusion coefficient, did not correlate with oil uptake. Migration was fastest in LLDPE and LDPE, followed by HDPE, and slowest in PP. Thereby, recycled materials consistently exhibited faster migration than virgin materials of the same type, showing a wide range of diffusion coefficients. Various properties were observed to understand the differences in migration behavior of HDPE. The key parameters influencing the migration included: ¥ Contamination with PP (0310%), ¥ Molecular structure variations, such as the amount of short-chain branches, and ¥ Polymer crystallinity. Lower crystallinity correlated with higher PP contamination or increased short-chain branching, both of which enhanced migration rates. These parameters are particularly significant in recycled materials due to inadequate separation processes of POs, other contaminants, and structural alterations during extrusion. Overall, recycled materials are inherently complex, with migration behavior driven by multiple factors, including feedstock, recycling methods, composition, and processing conditions, all of which influence the structure. Other properties, like molecular weight, molecular weight distribution, and contamination with other organic and inorganic substances, as well as mechanical properties, showed no correlation with the diffusion coefficient. Finally, the effect of material processing on oil migration was evaluated. Pellet samples were compared with IM pellets and extrusion blow molded bottles. No differences were observed in oil uptake and diffusion coefficient. Furthermore, the addition of a masterbatch also did not exhibit a correlation with migration behavior and was considered negligible. In conclusion, these results provide a comprehensive methodology for evaluating and monitoring the migration of cosmetic components into packaging materials. Differences within polymers, virgin and recycled materials, cosmetic components, and environmental conditions were analyzed. Specific parameters influencing the migration process were identified, offering potential strategies to minimize or prevent migration. However, polymers, particularly recycled ones, are complex systems with variable molecular structures and compositions that influence the migration behavior.