# Determining the Swelling Behavior and Tensile Strengths of Commercially Produced Buna‑N O‑Rings and Stereolithographic Additively Manufactured O‑Rings after Exposure to Mixtures Containing Jet Fuels, Synthetic Fuels, and Fuel Surrogate

## TL;DR

This study examines how different fuel mixtures affect the swelling and strength of O-rings made from Buna-N and stereolithographic materials.

## Contribution

The novel contribution is formulating a surrogate for ATJ-SPK and comparing the effects of various fuel mixtures on O-ring materials.

## Key findings

- ATJ-SPK and its surrogate caused less swelling in O-rings compared to JP-5.
- Adding cyclic and aromatic compounds increased swelling but decreased tensile strength.
- SLA O-rings showed lower tensile strength than Buna-N O-rings.

## Abstract

Synthetic fuels are among the portfolio of fuels that
enable operational
energy resilience. This work investigates the physical properties
of mixtures of military jet propellant fuel JP-5 with synthetic paraffinic
kerosene (alcohol-to-jet, ATJ-SPK), formulates a surrogate mixture
for ATJ-SPK, and explores the swelling behavior and tensile strengths
of commercially manufactured Buna-N O-rings and stereolithographic
additively manufactured (SLA) acrylate O-rings after exposure to fuels,
surrogate, and fuel mixtures with additives. An ATJ-SPK surrogate
was formulated (0.185 mole fraction of iso-cetane
in iso-dodecane isomers) whose density, speed of
sound, viscosity, flash point, and swelling matched those of ATJ-SPK.
ATJ-SPK and its surrogate swelled Buna-N (∼3%) and SLA (∼5%)
O-rings less than did JP-5 (∼23% Buna-N, ∼18% SLA).
Adding cyclic and aromatic compounds to mixtures of JP-5 with ATJ-SPK
or its surrogate increased swelling and decreased the tensile strength
of the O-ring. SLA O-rings had tensile strengths lower than those
of Buna-N O-rings. The densities of some mixtures met military fuel
specifications, while many flash points were too low. This work shows
that SLA O-rings can produce adequate swelling behavior and that cyclic
and aromatic compounds can be used to enhance swelling, but the fuel’s
physical properties must be examined to determine if they are adversely
impacted.