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Super strong plastic pipes will be lighter and last longer

A cross section showing a die-drawn pipe. Image: University of Bradford

Engineers at the University of Bradford have perfected a technique to give ordinary plastic pipes super strength.

The die-drawing process turns ordinary plastic into a lighter, stronger material – now the process is being commercialised by Saudia-Arabian company Sabic.

The new pipes outperform standard plastic plumbing pipes in pressure tests, are much cheaper to transport and last longer, and will therefore be more sustainable.

Sabic aims to capture 20% of the market with the new ‘biaxially oriented’ polyethylene and polypropylene pressure pipes.

Dr Fin Caton-Rose, who runs the research laboratory in the university’s globally-recognised Polymer IRC, said: “Biaxially orientated pipes are lighter and much stronger than traditional polyolefin pipes. They are cheaper to make, cheaper to transport and they last longer which means they are better for the environment.”

Plastic pipe before die-drawing process. Image: University of Bradford

Biaxially orientated pipes are created using ordinary plastic that has been drawn through a die, or in this case, through a die and over a mandrel – this process changes the properties of the plastic at the molecular level, making them far stronger and more durable than traditional plastic pipes.

Dr Caton-Rose explained: “Most people will be familiar with the plastic yokes that were widely used to keep cans together on supermarket shelves. If you were to pull those apart with your hands, you will notice part of the plastic turns white. This indicates you have changed the properties of that part of the plastic. If you were to then try to pull that apart, you will find you cannot, because it is now much stiffer.

“Pulling plastic through a die has a similar effect, in that it forces the molecules in the plastic to realign, so they are all facing the same direction, which makes it much stronger. In our biaxial pipes, we use a combination of a die and a mandrel to give us a balanced molecular alignment down the length of the pipe and through its thickness.”

Dr Ajay Taraiya, from Sabic, said: “Our collaboration with the University of Bradford is crucial in terms of the scientific-based research they are able to conduct, in order to accelerate solutions for commercial products.

“We selected the University of Bradford based on our needs and their expertise. Scientists there have a wealth of knowledge in the solid-phase deformation of polymers, in addition to world-class research facilities, not to mention globally recognised academics and a successful track record of industrial collaboration.”

University of Bradford technician Lee Thomas and Dr Ajay Taraiya from Sabic

Professor Phil Coates, who invented the die-drawing process, said: “This is an exemplary collaboration between a major global company with its significant research and development, plus commercial capabilities and a world-class polymer research laboratory. It is genuinely a win-win collaboration and serves as an example of how the kind of research universities do can have a direct impact on helping industry innovate.”

Over the past few years, SABIC and the University of Bradford have been involved in a successful collaboration to develop the process of biaxial stretching of polyolefin pipes. This has involved linking the material design to the structure and has led to the development of high performance pressure pipes. 

These results are being applied to the development of a commercial scale pilot line by Tecnomatic in Italy and Aquatherm in Germany, both in collaboration with SABIC.

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