KEY POINTS:
Professor Debes Bhattacharyya and his team at the Centre for Advanced Composite Materials at Tamaki have shown that one and one can equal three.
They have taken used plastic milk containers (made of polyethylene), and used Coke bottles (polyethylene terephthalate, or PET), and blended them together to create
a new material that is significantly greater than the sum of its parts.
The new polymer (plastic) composites being produced at the centre are not only much stronger than either of the original materials, they are also two or three times more effective at keeping out oxygen - making them highly suitable for packaging food products.
Bhattacharyya's group has designed and built a machine at the centre which is producing hundreds of metres of the new composites daily. He says they are excited about the implications of being able to take two source products and generate new materials that could be highly valuable to industry.
The secret of the group's success has been in overcoming the classic problem of composites: When a reinforcing fibre is added to a base material, defects often arise because of incompatibility between the two.
Bhattacharyya's group has discovered that this can be remedied if the two source materials have different melting temperatures (at variation of at least 40C).
Their work with polyethylene milk containers and PET Coke bottles shows that when the two are melted and stretched, the PET - which has the higher melting point - forms into tiny fibrils, or fibres, with diameters of just micro or nanometers.
As a result of the blending process, these fibrils are evenly distributed throughout the new material. "There are thousands and thousands of those fibrils in the material, all stretched and elongated in a particular direction, so you generate huge strength and stiffness," said Bhattacharyya.
"It's a fantastic way of creating a high-grade material from two low-grade materials."
Not only has the group proved that reject plastics can be transformed in this way, the composite materials themselves can be recycled several times with no reduction in their mechanical properties.
The researchers have also shown that by including suitable additives, the electromagnetic shielding properties of the material are also lifted, pointing to applications in electronic componentry and packaging.
The centre is also working on similar composites with biomedical applications. Last year it was contacted by a large American medical biomedical company (which Bhattacharyya says he can't name for confidentiality reasons), with which it is now working on a project to develop improved materials for stents and balloons used in cardiovascular surgery.
In the course of this work, the group has also discovered that by making a fibrillar composite reinforced with material acceptable to the human body, and then separating the reinforcing fabric, the new material could be used in tissue scaffolding - an area of medicine where support materials are inserted to restore function to damaged organs.
This work has been successfully tested in animals by the National University of Singapore.
"They have been received well by the animal tissues, and tissue growth has been fantastic," said Bhattacharyya.
The group is working with Auckland University's commercialisation arm UniServices to patent the oxygen barrier properties of the polyethylene/PET composites and the tissue scaffolding work.
Bhattacharyya's work in composites has put the centre on the map - in the past year he and colleague Professor Stoyko Fakirov have been invited to give eight international conference presentations, and the centre has received calls from around the world from companies interested in the new materials being created.
But he would like to see the work commercialised in New Zealand for the benefit of local industry - although past experience shows that's not easy.
In 2000 a process he developed with two doctoral students for roll-forming fibre-reinforced thermoplastic sheets was sold to a Florida firm because there were no takers for it in New Zealand.
Seven years on, he's hoping the New Zealand business and venture capital communities' appetite for taking new high-tech materials to market has increased.
"We have one or two [New Zealand] companies in our mind and we have spoken to them, they have shown interest, and we are manufacturing some products to convince them. We will soon have all the data and we can start talking to them more seriously."
