Nouryon contributes to the development of composite materials made from natural fibers, such as flax. This development includes renewable constituents such as biofiber reinforcements to make recyclable composites with high bio-content for the transport and electronics industries. For example, the Floriade Bridge, a project developed and implemented in 2022 in the Netherlands, is a remarkable example where innovative curing systems and the desired closure of the lifecycle of a thermoset composite end products coincided.


The innovative curing systems offered by Nouryon bring great value to a sustainable trend and desire for weight reduction, reduced fuel consumption and carbon footprint, increased bio-content and enabling recyclability. This can be achieved, for example, by replacing glass reinforcement with flax fibers. For the use of flax fibers as reinforcements in unsaturated polyester resins (UP), the new curing systems have proven to be instrumental and necessary.

Nouryon's new range of curing systems for composite material are non-sensitive to water and therefore provide excellent curing in flax fiber reinforced composites based on unsaturated polyester resins. These curing systems do not require prior drying of the biofibers, enabling energy cost savings. This makes it possible to build large end products, such as bridges and large flat panels for truck trailers.

In addition, the use of biofibers in the production of these larger end-products helps the composite market to meet sustainability targets for weight reduction. By using biofibers, the bio-content of the end-products increases and the use of glass as reinforcement can be reduced. In fact, the reduction of fuel-intensive glass production contributes to sustainability.

Making sustainable bridges using natural fibers

The use of natural fibers in composites is up till recently mainly limited to the automotive industry, where polypropylene is used as binder material. With UP resins, the use of natural fibers has been more challenging as the water content in the biofibers affects the curing process in a negative way.

Natural fibers such as flax contain up to 12% water. Curing composites based on flax fibers is therefore challenging, if not impossible, when using conventional cobalt-based curing systems. Cobalt-based curing systems are prone to hydrolyze under the influence of water and become unreactive to the curing process.

The flax fibers must therefore be dried before use. This requires an oven, which consumes a large amount of energy and has a negative impact on the CO2 footprint. In addition, the dried fibers must be stored in a confined condition to avoid the reabsorption of moisture from the air. For these reasons, the use of natural fibers in UP resin composites has so far mainly been successful in small sized end-products such as scooters, chairs, and tabletops.

Flax plants used for natural fibers

Nouryon’s new curing systems solve this problem, as they are not sensitive to water when curing UP resins with high water content. This allows customers to work with wet filler materials, such as non-dried natural fibers.

“By curing composite materials with Nouryon’s curing systems, customers can easily switch from glass to flax fibers while maintaining mechanical properties,” said Roel Zuijderduin, Global Technical Development Manager at Nouryon Polymers Specialties. “With this, customers don’t have to dry the flax and store it under restricted conditions. Instead, they can start using biofibers in their composite end-products and produce larger objects, which makes the use of natural fibers easy and affordable.”

Nouryon aspires to be a net-zero organization by 2050. Read more about how our R&D pipeline is focused on solutions with sustainability benefits.

Discover Nouryon’s curing systems, Nouryact® accelerators, for biofiber reinforced composites and check the Smart Circular Bridge live data here

Any further questions, please feel free to contact us.

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