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Sustainability Science: Ensuring Recycled Polyester Claims Are Genuine

Growing demand for sustainable products from consumers, governments and NGOs has made the use of recycled materials in fashion tremendously valuable to brands as well as the environment.

The global fibers market is dominated by polyester, and given that one ton of recycled polyester saves 11,100 kWh of energy—the equivalent of two years of energy consumption for an average household—the use of recycled polyester in textiles is rising sharply. PET accounts for approximately 55 percent of the total volume of fibers produced globally. Today, the average percentage of recycled polyester in textiles is 15 percent, and initiatives such as Textile Exchange’s 2025 Recycled Polyester Challenge are driving the apparel industry to boost that number to 45 percent by 2025.

As mindful consumers become more aware and critical of sustainability claims, brands and retailers must be able to back up the use of recycled polyester in their products with proof. Until now, the primary way to attest the inclusion of recycled polyester has been to rely on declarations and documents from suppliers and third parties. By betting on someone else’s information, brands risk greenwashing (claiming something as sustainable when it isn’t) and breaching regulations. For instance, the E.U. and GRS-V3 impose a minimum recycled polyester content of 20 percent.

Putting the control in the hands of brands, SgT and Worms Safety Laboratories have developed an innovative proprietary method that accurately detects and quantifies the amount of recycled polyester in textiles.

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What is recycled polyester?

Of the 57 million tons of polyester (PET) used each year worldwide, the apparel industry accounts for more than half of that at 32 million tons. To create virgin polyester, or PET–the world’s most common plastic—crude oil and natural gas are extracted from the earth and heated to form a resin. The resin is spun into fibers to create polyester fabric or molded into plastic containers. These products aren’t biodegradable and will persist in the environment, even as they eventually break down.

Recycled polyester (rPET) comes primarily from post-consumer PET bottles that are melted down and re-spun into new polyester fibers. Each kilogram of mechanically recycled polyester represents a reduction in greenhouse gas emissions of more than 70 percent compared with virgin polyester.

A scientific solution to verify recycled polyester

Following years of research, SgT and Worms Safety Laboratories have pioneered an innovative solution to detect and quantify rPET in textiles to prove its existence in products and avoid greenwashing. Among many possible methods, the most suited method is based on nuclear magnetic resonance (NMR) technology, which is highly sensitive, robust, accurate, auto-calibrated and not affected by additional chemical substances such as dyes, viscose or others.

In simple terms, the process targets the presence of isophthalic acid (IPA), which is added to PET to give specific properties to the raw material for bottle manufacturing. This new testing method uses NMR technology to compare the IPA content in each testing sample to the average IPA content derived from a reference database of bottles collected in Europe, China and India.

More accurate than any other method

Other methods are available to measure IPA, including Fourier transform infrared spectroscopy, near infrared Raman spectroscopy, liquid chromatography and gas chromatography. However, the common disadvantage of these processes is the generally higher uncertainty of the test equipment and the sensitivity to other substances present in the sample.

The new method developed by SgT and Worms Safety Laboratories is highly sensitive and specific, with low detection limit and greater certainty. The PET bottle reference library is continuously monitored and updated, and any changes in PET quality on the market will be reflected in the test results.

Even if you know your supply chain, relying solely on someone else’s information and declarations is inherently risky. Accurate scientific testing is the only way to be 100 percent sure that the amount of rPET in your products matches what you say it is.

This article has been written with the support of Dr. Samuel Legoupil, who has 20 years of experience in industrial innovation at CEA Tech, the first research and technology organization in Europe. His work includes the development of cutting-edge quality control methods for manufacturing industries such as automotive, aero, energy and space. He is currently Chief Technology Officer at Worms Safety.

Click here to learn more about SgT. For more on this topic, watch SgT’s webinar here.