Experimental Comparison of Elastomeric Materials for Hydraulic Seal Durability Under Reciprocating Conditions

Wave Energy Converters (WECs) depend on hydraulic Power Take-Off (PTO) systems in which elastomeric seals must withstand wear, fatigue, and corrosion under harsh marine loading. This study quantitatively compares two commercial polyurethane seals (E1-E2) with custom-compounded Ethylene propylene diene monomer rubber (EPDM) formulations (E3-E5) using reciprocating wear tests (ASTM G133) at 3-10 N and 10-30 mm/s. It is noted that all experiments were conducted under dry conditions at room temperature as a baseline assessment, and the findings provide foundational insight prior to considering lubrication, hydraulic fluid effects, and marine environmental conditions relevant to WEC operation. Coefficient of friction (COF), specific wear rate, and worn-surface morphology were assessed to determine material durability. The commercial thermoplastic polyurethane (TPU) grades exhibited high hardness (93-94 Shore A), low wear rates (2.29-1.93 × 10^-4 mm³/Nm), and shallow wear scars (≤380 µm). Carbon-black-reinforced EPDM (E3) produced the lowest wear rate among all samples (1.45 × 10^-4 mm³ N^-1 m^-1) and the longest predicted service life (6.2 years), whereas silica-filled and plasticized EPDMs (E4, E5) showed higher wear (2.44-2.88 × 10^-4 mm³/Nm) and broader deformation zones. Archard-based lifetime estimates at 10 N and 30 mm/s ranged from 3.1 to 6.2 years across materials. These results demonstrate that optimized EPDM formulations can serve as cost-effective alternatives to commercial TPUs for medium-load hydraulic sealing applications while providing a quantitative basis for material selection and life prediction.