Bioplastics save cost as well as the environment

Researchers in Malaysia have developed low cost polymer based materials using natural and waste products.

Low cost coatings, polymers and composites derived from natural and waste agricultural products have long been a major feature of research and development efforts in Malaysia. This should come as no surprise coming from a country that is one of the world's largest producers of that major natural and sustainable polymer; rubber.

In a fusion of old and new technologies, Professor Azizah Ahmad from the Universiti Teknologi MARA in Selangor explains that if Dammar resin is mixed with nano clay and silicon, it produces an extremely tough coating that is suitable for use on steel.

Dammar is a natural gum that is extracted from Dipterocarpaceae trees in a similar manner to rubber and has been used for nearly two centuries to make varnish. In Malaysia it is very cheap and the combination of these materials stands up particularly well in scratch tests. It is also water repellent, does not crack, and makes a good thermal barrier. The base resin melts at 120ºC. To make it a truly a sustainable product it can be coloured black using carbonised palm kernel, which is a waste product.

There is also a movement toward sustainable materials derived from agricultural wastes. Mohammed Bin Kamarudin, also from the Universiti Teknologi MARA, has developed a thermal insulating board that makes use of the remarkable engineering properties of crushed eggshells. Despite the delicate nature of whole eggs, crushed eggshell is quite strong.

The shells also possess natural micro pores to allow oxygen to pass through which incidentally makes the material a good thermal insulator. Kamarudin has been developing a composite of crushed eggshell in polystyrene as an alternative to commercial gypsum board for the building industry.

However, this has potential far beyond buildings since it has a flexural strength of 61MPa, slightly below that of polystyrene, but a stiffness of 7.5GPa, a tensile strength of 32MPa and a thermal conductivity of 0.873W/mºC at 100ºC. Since it is about half the price of gypsum board, it should also appeal to automotive designers.

The other Malaysian development area already a major commercial product in South Africa, is composite plastic, usually polypropylene, reinforced with Kenaf. It is delivered by Sustainable Fibre Solutions (SFS) to BMW, Daimler Chrysler, Toyota, GM, VW and Nissan.

Kenaf is a herbaceous plant which grows 1.5m to 3.5m tall. Its main uses were originally, rope, twine, coarse cloth and paper. But Dr Khalina Adban of the Universiti Putra Malaysia has been improving its rheology and mechanical properties using a radiation treatment.

Kenaf produces two kinds of fibre, coarse 'bast' fibre in its outer layers and a finer fibre in the core. It is the bast fibres that are used as part of a composite. SFS says that it imparts greater strength and dimensional stability but permits rapid production and deeper 3D moulding. Natural fibres in general provide stiffness enhancement and acoustic damping at lower cost and density than glass fibres and mineral fillers, resulting in greater strength to weight ratios.

Author
Tom Shelley

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