Zeolites as odor scavengers for plastics and recyclates

Recycling is a key element in achieving a sustainable circular plastics economy. However, many challenges remain. One major challenge affecting the quality of plastics and recyclates is the presence of unpleasant odors. Odor reduction can be achieved using odor scavengers - additives that work by either reacting with or absorbing odorous compounds.
Zeolites are well known for their adsorptive properties and are therefore commonly used as odor absorbers. However, the effectiveness of an odor absorber strongly depends on the odorant and the type of recycled polymer. Finding a zeolite that meets these requirements is a time-consuming and costly process. Furthermore, many challenges remain regarding the interactions of odor absorbers with other additives in the product, e.g. plastic stabilizers.
This study presents a three-step characterization cascade to evaluate zeolites as odor scavengers for odorous materials. One step involves a rapid test to determine the amounts of volatile organic compounds (VOCs) and semi-volatile compounds (FOGs) captured by the zeolites, which allows for the pre-selection of promising additives. Another step focuses on compounding the polymers with the zeolites and other additives to assess the stability and aging of the resulting compounds. Additionally, test specimens of odorous materials containing the zeolites are prepared, and their odor is evaluated by human sensory analysis.