PE‐RT Grades for High‐Temperature Flexible Risers: Comparative Evaluation of Thermal, Mechanical, and Aging Performance

This study compares three polyethylene grades—a benchmark PE100 and two high‐temperature resistant polyethylene (PE‐RT) types (Type I and Type II)—to assess their suitability for flexible riser applications. The materials were evaluated for their thermal stability, crystallinity, mechanical performance, and resistance to thermal aging at 110°C for up to 180 days. Differential scanning calorimetry (DSC) and x‐ray diffraction (XRD) indicated that PE‐RT Type II had a higher degree of crystallinity. Thermogravimetric analysis (TGA) showed that PE100 had the highest T onset (457°C), confirming its superior thermal stability. However, PE‐RT Type II was the most promising material, showing a balanced response to thermal and chemical stress with excellent thermo‐oxidative durability, flexibility, and aging resistance. The tensile test results demonstrated that PE‐RT Type II consistently outperformed PE‐RT Type I in mechanical strength and durability. After aging tests performed in synthetic oil at 80°C for 180 days, PE‐RT Type II retained approximately 85% of its original elongation at break and 90% of its initial tensile strength. In contrast, PE‐RT Type I exhibited a significant reduction in performance, retaining only about 42% of its original elongation and 70% of its tensile strength. These results indicate that PE‐RT Type II is more resistant to thermal and oxidative degradation, reinforcing its suitability for long‐term use in high‐temperature flexible riser systems. Fourier‐transform infrared (FTIR) spectroscopy revealed more significant oxidation in Type I, suggesting lower resistance to thermo‐oxidative degradation. Overall, PE‐RT Type II displayed an enhanced balance of properties, making it the most promising candidate among the evaluated materials for application in high‐temperature flexible riser barrier layers.