Additively Manufactured O-rings: Tensile Strength and Swelling Behavior in the Presence of Gasoline and Surrogate Mixtures

This work investigates the swelling and physical properties of additively manufactured (AM) acrylate and traditionally manufactured (TM) O-rings when exposed to gasoline and organic mixtures. Fuel chemical compositions were determined using gas chromatography/mass spectrometry. Polymer properties were found using differential scanning calorimetry, thermal gravimetric analysis, and tensile testing. Exposure to gasoline for 24 h caused the AM and TM O-ring to lose from 54 to 80% of their unexposed failure strength. AM O-ring failure strength varied more (~ 20%) than TM O-rings (~ 7%). AM O-rings swelled from 46 to 110% with greater swelling in E10 than in E85 or ethanol-free gasolines. Volume changes ranged from −5 to 175% for commercial polymers. Aromatic compounds increased O-ring swelling. For ternary mixtures with 30% toluene, decane, and ethanol, increasing the ethanol up to mass 35% increased the swelling from 30 to 100 vol.%, after which the swelling remained level. Subsequent fuel evaporation from the polymers returned most of them to their original size and tensile strength, suggesting that the 24-h exposure caused no permanent damage. One AM O-ring exposed to 30% toluene/70% ethanol showed visible structural changes accompanied by a tensile strength less than half that of those with no visible changes.