Analysis of Sunlight-Induced Strain Variations in High-Density and Linear Low-Density Polyethylene Blends.

Abstract

This study evaluates the effect of prolonged sunlight exposure on the strain behavior of High‑Density Polyethylene (HDPE) and Linear Low‑Density Polyethylene (LLDPE) blends, with emphasis on the rate of mechanical degradation across varying compositions. Six blend ratios—100:0, 90:10, 80:20, 70:30, 60:40, and 50:50 (HDPE:LLDPE)—were subjected to tensile loading, and strain values were recorded at intervals of 60 s, 120 s, 180 s, 240 s, 300 s, 360 s, 420 s, 480 s, 540 s, and 600 s. Prior to exposure, the materials exhibited high strain capacities, with pure HDPE reaching 0.77 mm at 60 s and 5.23 mm at 600 s, while the 50:50 blend recorded 0.48 mm at 60 s and 4.90 mm at 600 s, indicating good viscoelastic behavior. After four weeks of sunlight exposure, strain values declined across all blends; for example, at 60 s pure HDPE reduced from 0.77 mm to 0.65 mm, while the 50:50 blend dropped from 0.48 mm to 0.35 mm. After nine weeks, the strain values declined further, with HDPE reducing to 0.60 mm and the 50:50 blend to 0.30 mm at 60 s. After seventeen weeks of exposure, the lowest strain values were recorded: HDPE decreased to 0.50 mm and the 50:50 blend to 0.20 mm at 60 s, representing a reduction of approximately 35% and 58% respectively from initial values. Similar patterns were observed at longer loading times, demonstrating cumulative degradation.These results confirm that mechanical degradation increases with LLDPE content and exposure duration, while HDPE‑rich blends (e.g., 100:0 and 90:10) maintain higher strain retention and better resistance to UV‑induced embrittlement. The findings highlight the importance of selecting suitable HDPE/LLDPE ratios for outdoor applications and suggest that incorporating UV stabilizers can further improve performance in sunlight‑exposed environments.