From recycled bottles to water pipes

"It turned out that the pipelining material had brown and gray traces," says Matthias Peppel, Product Manager for Trelleborg’s rehabilitation products in Germany. "Some of our customers use UV light to cure the resins in the liner and therefore we have special requirements for color."

The Trelleborg pipe repair team therefore developed a color specification tailored for UV-cured applications and soon found a supplier capable of delivering sufficiently white or translucent fibers.

Lower emissions

Since the end of 2024, all the Thermoliner Plus produced by Trelleborg has been made from recycled polyethylene terephthalate (rPET) fiber.

“It is a no-brainer to use rPET for the purpose that we use it for, because you may not be able to use it for other more technical applications,” he adds.

Trelleborg estimates that using rPET instead of virgin PET (vPET) reduces the CO2 emitted in the manufacture of its Thermoliner Plus textile by up to 79 percent, without any impact on cost or performance. This comes on top of the existing benefits of PET: relining old pipes even with vPET, as opposed to rPET, leads to 70 to 78 percent lower carbon emissions than replacing them with new pipes, while using PET for a product with a design life of 50 years also functions as a form of waste disposal. Given that currently only a little over half of

PET produced is recycled even in Europe (it’s a third in the US), that is a significant advantage.

Growing business

The sheer number of pipes requiring replacement or repair across Europe, as infrastructure built in the boom of the 1950’s reaches the end of its useful life, means that the total CO2 saving could be considerable.

"For instance, there is work for the entire labor force employed in the field in Germany for the next 50 years, and once those 50 years are over, we will reach the design life of the pipes that we are building now,” Peppel says. “So, you can just start all over again."

Virgin PET, he believes, is best reserved for products where the technical requirements make it necessary.

Next in Line

Trelleborg started with its Thermoliner Plus material range first, because the structural properties required for the product, which is used for relining sections of pipe with bends of no more than 45 degrees, are less demanding. The molecular weight, chain length, and crystallinity of PET degrade during recycling, making rPET more brittle and harder to spin into long fibers.

A 2020 study from the Indian Institute of Technology in Delhi, estimated that rPET had 15 percent lower tensile strength, or tenacity, than vPET. This in turn makes rPET harder to use for knitted fabrics than for a needle felt with relatively short fibers, such as that used for Thermoliner Plus.

For this purpose, rPET easily meets the two key requirements for the liner: a good chemical resistance, so the material does not degrade over time, and a high level of absorbency so it fuses with resin. Other Trelleborg pipe liner products such as Ultraflex and MultiFlex, which can be used in pipes with dimension changes or bends of 90 degrees or more, are more of a challenge.

"The fibers for these products have to first be formed into a thread and then knitted to form the carrier, so that will be a different story, and may involve a little more work," Peppel explains.

He is confident nonetheless that rPET can ultimately be used for almost every liner in Trelleborg's portfolio, with Ultraflex the next product in which vPET is set to be replaced.

Liners act as carriers for resin, which then sets inside it, building a laminate which forms a new, seamless and leak-tight pipe inside the old one. The new pipe, effectively manufactured in situ, meets the same technical requirements as the old pipe did.

Trelleborg polymer chemist for pipe repairs, Juan Dominguez, has also shown that about 20 to 25 percent of the material that goes into the company’s resins can be replaced with renewable, plant-based materials, meaning the total solution's embodied carbon emissions can be reduced still further.

Market differentiator

Trelleborg has a clear focus on reducing its climate footprint and set a target in 2022 to halve its Scope 1 and 2 emissions by 2030. That target was already achieved in 2024, six years ahead of schedule, and new targets are now being set to continue reducing the Group's climate impact.Sustainability and CO2 emissions are increasingly on the agenda for stakeholders in the trenchless pipe repair market. In some regions, such as the Nordics, the CO2 impact of the products used is already taken into account in public tenders and can therefore be the decisive factor for winning a contract alongside price. For these customers, the changes Trelleborg has made are already a significant advantage. The shift to rPET in Thermoliner Plus demonstrates that making substantial savings in carbon emissions does not always require investing in research and development, bring additional costs, or require compromises in performance.

"It was not magic and it was nothing that took us years and years,” Peppel concludes. “But it shows that with a little effort, you can make a difference.”

Visit Trelleborg.com for further insights on solutions for trenchless pipe rehabilitation.