How Sunlight Transforms Polyethylene and Promotes Microplastic Formation from Greenhouses

Linear low-density polyethylene (LLDPE) is widely used in agricultural films, packaging, and everyday products. Although it may appear stable, ultraviolet (UV) radiation, oxygen, moisture, and temperature fluctuations can progressively alter its structure. This article explains how LLDPE films age and how chemical oxidation, molecular rearrangement, surface damage, and embrittlement can promote fragmentation and microplastic formation. The underlying study compared outdoor weathering in Urcuqu´ı, Ecuador, for up to 342 days with controlled irradiation at 365 nm using a 50-W LED for up to 579 hours. ATR-FTIR tracked oxidation through the carbonyl index, Raman spectroscopy monitored conformational changes, and scanning electron microscopy (SEM) documented surface defects. The carbonyl index increased from approximately 0.03 to 0.22 after 342 days outdoors, compared with approximately 0.08 after 400 hours under controlled UV exposure. Defective surface area also increased under both conditions. These findings support a coupled degradation process involving oxidation, chain scission, structural rearrangement, and surface embrittlement. The article also discusses greenhouse-plastic waste management in Ecuador and presents a qualified, order-of-magnitude estimate of potential annual film replacement. The estimate is not an official waste inventory; it illustrates why timely removal, collection, and recycling of aged films are important.