Comparison of oil resistance and adhesion durability between polysulfide sealant and polyurethane sealant

Abstract

Sealants are widely used in structural applications requiring mechanical strength and environmental resistance. This study compares the thermal, mechanical, and oil resistance properties of polyurethane (PU) and polysulfide (PSF) sealants. PU exhibits high tensile strength and adhesion due to strong hydrogen bonding, while PSF shows higher elongation but poor adhesion. Fractographic analysis reveals brittle failure in PU and ductile features in PSF. Upon kerosene immersion, PU undergoes severe swelling and a drastic reduction in lap shear strength (84.6 %), whereas PSF shows minor surface adsorption and lower degradation (22.3 %). PSF offers excellent oil resistance, its limited adhesion restricts structural use. PU shows superior mechanical performance but poor oil resistance. PU sealants require modification through crosslinking, incorporation of hydrophobic additives, or surface treatment to overcome this trade-off. These results highlight the need for a hybrid approach that combines mechanical advantages of PU with chemical resistance of PSF for high-performance sealants in harsh environments.