Determination of degradation products derived from oxidation processes on plastic films versus time.
The goal of the study was to understand the formation of compounds during the aging of plastics, in particular polyethylene, and to determine the substances that are formed during the degradation processes of plastic films exposed to UV radiation.
The study used two aging methods: one using an open chamber accelerated aging cell (Q-Lab’s QUV UV) in which the sample is directly exposed to the atmosphere, and one in a closed chamber designed by LMPE researchers, where the oxygen content is monitored by optical sensors via the Ametek instrument (optech O2 Platinum).
The aging of the material was evaluated by monitoring the carbonyl index (determined by infrared spectroscopy FTIR-ATR Perkin Elmer Spectrum model two) and the embrittlement of the samples measured by Shimatzu electromechanical dynamometer (AGS-X 10-10KN) with periodic evaluation of degradation products by the techniques shown in the table.
Analysis showed that the aging process leads to a reduction in the molecular weight of the polymer by about 10 times after 300 hours of irradiation. In addition, changes have occurred to the thermal resistance and crystallinity of the material.
Finally, UV exposure caused the formation of ketone/aldehyde and carboxylic compounds, alkyne and alkene systems, and products with multiple functional groups in the molecular chain (as shown by the GC-MS and NMR analyses, both outsourced to Partner Universities). It also observed the formation of fatty acid-like compounds, their most oxygenated derivatives, and unsaturated systems following exposure to UV rays.
This method is useful to monitor the aging and determine the shelf life of a material over time (shelf life), as well as identify the substances released into the environment during the degradation process.