posted on 2020-03-31, 19:45authored byLinhong Xiao, Ziye Zheng, Knut Irgum, Patrik L. Andersson
Plastic materials contain various
additives, which can be released
during the entire lifespan of plastics and pose a threat to the environment
and human health. Despite our knowledge on leakage of additives from
products, accurate and rapid approaches to study emission kinetics
are largely lacking, in particular, methodologies that can provide
in-depth understanding of polymer/additive interactions. Here, we
report on a novel approach using quartz crystal microbalance (QCM)
to measure emissions of additives to water from polymer films spin-coated
on quartz crystals. The methodology, being accurate and reproducible
with a standard error of ±2.4%, was applied to a range of organophosphate
esters (OPEs) and polymers with varying physicochemical properties.
The release of most OPEs reached an apparent steady-state within 10
h. The release curves for the studied OPEs could be fitted using a
Weibull model, which shows that the release is a two-phase process
with an initial fast phase driven by partitioning of OPEs readily
available at or close to the polymer film surface, and a slower phase
dominated by diffusion in the polymer. The kinetics of the first emission
phase was mainly correlated with the hydrophobicity of the OPEs, whereas
the diffusion phase was weakly correlated with molecular size. The
developed QCM-based method for assessing and studying release of organic
chemicals from a polymeric matrix is well suited for rapid screening
of additives in efforts to identify more sustainable replacement polymer
additives with lower emission potential.