Environmental aging of polymers to evaluate their use in remediating natural gas pipelines

Document Type

Presentation

Date of Original Version

3-27-2026

Abstract

The United States natural gas distribution system consists of more than 2.3 million miles of pipelines that deliver natural gas to homes and businesses. Many sections of this network were built decades ago using cast iron, particularly in older urban areas. Over time, cast iron pipelines can deteriorate due to corrosion, cracking, and long-term environmental exposure. These failures can lead to gas leaks that pose risks to public safety and create significant economic costs. One promising strategy for addressing this challenge is the use of polymeric liners that can be installed inside existing pipelines using trenchless rehabilitation methods. These approaches avoid large-scale excavation, reduce disruption to surrounding infrastructure, and provide a cost-effective way to extend the service life of aging pipelines. However, to ensure their long-term reliability, it is important to understand how polymer materials behave when exposed to natural gas environments over extended periods of time. In this work, we investigate the effects of natural gas exposure on several industrial polymers that are commonly considered for pipeline liners, including high-density-polyethylene (HDPE), polyamide (PA), and polyvinylidene difluoride (PVDF). Samples were exposed to model natural gas mixtures under elevated temperature and pressure conditions designed to simulate long-term service environments. The materials were then characterized using dynamic mechanical analysis (DMA), quasistatic tensile testing, and Fourier transform infrared spectroscopy (FTIR) to evaluate changes in their mechanical, chemical, and dynamical behavior. Our results show that the primary mechanical properties of the polymers remain largely unchanged after exposure to natural gas. However, more subtle changes are observed in the way polymer chains move and relax over time. These changes are quantified using time–temperature superposition, which allows us to analyze the relaxation behavior of polymers across long time scales. From this analysis, we extract the activation energy associated with polymer relaxation processes. Activation energy in this context does not describe how strong the material is at a given moment. Instead, it reflects how quickly the internal molecular structure of the polymer evolves over long periods of time. In other words, activation energy is not about how strong the material is today—it is about how fast its properties may change over decades. After exposure to natural gas, we observe a measurable decrease in this activation energy, indicating that absorbed gas molecules act as plasticizers that slightly increase the mobility of polymer chains. Importantly, these changes are largely reversible when the samples are removed from the gas environment, suggesting that the effect arises primarily from physical absorption of gas molecules rather than permanent chemical degradation. Overall, these results show that polymer liners retain their mechanical strength while experiencing modest and reversible changes in their molecular dynamics. This work provides important insight into the long-term performance of polymer materials in natural gas environments and supports their use as a practical and effective solution for rehabilitating aging pipeline infrastructure.

This document is currently not available here.

Share

COinS