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New resins strengthen pipe repair industry

For over 20 years the clay pipes of the world's sewage systems have been repaired with resins and composites containing synthetic ingredients made of crude oil. Growing pressure to use environmentally benign materials, alongside a pressing need to improve adhesive strength, prompted Hungarian and German partners to develop a new generation of high-performance pipe repair products made with vegetable oils.

"Vitrified clay pipes have a glazed surface that makes adhesion difficult and a strong bond with composite repair rings is critical to withstand cleaning with powerful water jets. In Germany it is now obligatory to mill the surface to create a matte finish and improve adhesion, but milling takes time and costs money", explains Dr Tamas Balogh of Polinvent, the manufacturer of resins for short pipe segment repairs which led the EUREKA COMPONAT project.

Polinvent recognised the economic potential of developing resins and composites with outstanding adhesion to shiny surfaces without milling. It also saw the opportunity to future-proof the industry in the face of environmental and regulatory pressure by replacing the crude oil-based raw materials in existing resins with renewable materials. And these advances, it believed, could also lead to improved technical properties and overall performance - and extensive international applications.

Rising to the challenge

As a small niche supplier, Polinvent knew it needed to join forces with scientific experts and end users to bring the new plant-based resins into being and to market. "We are in the middle of our two partners," says Dr Balogh. "On one side is the Institute for Composite Materials of the Technical University in Kaiserslautern, which has long experience with similar resins. On the other side is Fluvius GmbH, a major exporter of wastewater pipe repair products which works closely with field engineers and understands exactly what they want from its products."

As a small niche supplier, Polinvent knew it needed to join forces with scientific experts and end users 

Through EUREKA, the partners were able to secure Hungarian and German government funding: the Hungarian part of the project was funded by the EUREKA_HU_13 Programme. The call published by the National Research, Development and Innovation Office aims to support the participation of Hungarian institutions in the international collaborative EUREKA projects by providing the necessary Hungarian funds. The German part of the project was funded by the central innovation programme for SMEs (ZIM), a funding programme of the Federal Ministry for Economic Affairs and Energy (BMWi).

In the project, the partners got to work experimenting with 832 different material compositions. "The challenge was to identify the most promising vegetable oils, look at their ratios of adherence strength, workability time and hardening time and fine tune these to optimise key parameters so the new resins imitate, or improve on, the behaviour of resins currently in use," explains Dr Balogh.

Finding unexpected markets

Linseed oil had been expected to deliver the desired results, but it turned out that cashew nut oil and pine needle oil were the best-performing options. Financial and ethical factors came into play in their selection too: they are not as expensive as many others and don't affect the food market in developing countries as they are not fit for human consumption. Novel resins incorporating these oils were then used to make composites with stronger adhesion, longer storage life and higher heat resistance compared to their predecessors.

The market has judged the new resins and composites very positively and while they cost €1 more per kilogram this is still a significant saving compared to the cost of milling. There is an expectation that sewage system applications requiring especially high strength joining materials will lead to more sales in the future. In the meantime, Polinvent has discovered two new markets. It has supplied the resin to coat industrial flooring for a major pharmaceutical firm and to make corrosion protection coatings for stainless steel tanks at the Hungarian plant of a German chemical and consumer goods manufacturer. 

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