Effect of Lacticaseibacillus paracasei, extracted from an aircraft fuel system in marine environment, on the performance of modified polysulfide-sealed rubber

In aircraft fuel systems, rubber is commonly used to seal and connect components such as pipes and valves. Microbially influenced corrosion (MIC) leads to the aging, expansion and deformation of rubber, potentially impacting the sealing and safety of fuel systems. In this study, we focused on isolating a typical microorganism, Lacticaseibacillus paracasei (L. paracasei), found in an aircraft fuel system in marine environment and our investigation aimed to assess the impact of L. paracasei on the mechanical properties of modified polysulfide-sealed rubber using a series of measurements of tensile strength, hardness and permanent compression. The results indicated that with the increasing immersion time, the tensile strength, hardness and elongation-at-break of rubber all decreased, while the permanent compression deformation rate increased. Upon observing the morphology of the rubber before and after immersion, we discovered pits and precipitated granular substances on the rubber surface within the L. paracasei system. At the same time, through scanning electron microscopy examination of the rubber fracture surface after microbial immersion, distinct smooth regions were identified at the edge, indicating a severe degree of degradation. In addition, the results of the infrared spectroscopy analysis revealed that L. paracasei caused damage to the double bond chains of the rubber, resulting in degradation in its performance.