The impact of navy jet fuel (JP-5) and diesel fuel (F-76) on the swelling and tensile strength of additivity-manufactured and commercially-manufactured O-rings

Abstract

This work explored the effect of military jet (JP-5) and diesel (F-76) fuels, surrogate mixtures, and pure compounds on the swelling and tensile strength of additively-manufactured (AM) acrylate O-rings and commercially-produced acrylate, nitrile, and Ford Motorcraft O-rings. The composition of the fuel was determined using two-dimensional gas chromatography (GC × GC) and the uptake of the organic compounds from surrogate mixtures into the AM O-rings was determined using gas chromatography. Exposure of the O-rings to various organic mixtures for 7 days produced volume changes that ranged from −3 to 155% for AM O-rings, 0 to 130% for commercial acylate O-rings, 1 to 260% for Buna-N O-rings, and −4 to 3% for Ford Motorcraft O-rings. The greatest swellings were found for the aromatic compounds followed by the cycloalkanes. JP-5 and F-76 fuels caused the AM O-rings to swell by 15.2 and 11.6%, respectively. A jet fuel surrogate containing 10% dodecane, 51% isocetane, 15% butylbenzene and 24% butylcyclohexane produced a similar swell (14.9%) to that of the JP-5, which contained 10.9% aromatics, 5.6% cycloaromatics, and 25% cycloalkanes. Diesel fuel surrogates containing 1-methylnapthalene produced much higher swells in the AM polymers (greater than 22%) than did the diesel fuel, illustrating that while this component may be good for enabling diesel surrogates to emulate the physical and combustion properties of diesel fuel, it also comes with increased swelling. Tensile strengths of the swollen O-rings were reduced by as much 90%. Evaporation of the fuels and components from the O-rings for more than 3 weeks returned most of the O-rings to their original size and tensile strength, suggesting that the short-term exposure did not adversely affect the O-rings.