Going Bananas in the Search for Greener Composites

In the ever-growing search to find cheaper, greener solutions to today’s inorganic advanced composites, scientists in Columbia are hoping to make the waste material from banana farms compete with modern glass and carbon fibre products.

In Colombia, banana cultivation provides employment to over 170,000 people, according to data collected by the Ministry of Agriculture and rural development in 2011 353,297 hectares were cultivated, with a production of 2,815,693 tonnes. The leaves and stalks that are leftover from this farming, instead of being wasted could be used in the creation of banana fibre brining in additional revenue to the industry.

A project from the Department of Industrial Engineering of the National University of Colombia, in Manizales, managed to use the plant’s stalk to obtain a high quality reinforcing material.

Natural fibres in contrast to inorganic materials such as glass and carbon fibre are irregular due to their cellulose, hemi-cellulose and lignin composition, which makes them unsuitable for reinforcing materials. In order to change this, Lady Johana Rodríguez, Master in Industrial Engineering, developed a chemical process which modifies the internal structure of banana fibres. This innovation makes it possible to obtain more uniform surfaces, with a better resistance to environmental corrosion, high temperatures and water absorption (they are hydrophobic).
The treatment consists in their submersion, for 24 hours, in a compound made of epichlorohydrin, an anhydrous acetic reactant and acetone. They are washed in acetone and distilled water and dried in an oven for a day. They are afterwards tested for resistance, hydrophility (water absorption), heat and alkalinity.

Once treated the fibres repelled water by up to 33.3% and resistance to air moisture increased by 32.43%, extending durability. Additionally, using micrographs made with scanning electron microscopes, it was observed that the surface was smoother, leading to a perfect adhesion to the polymer matrix,” stated the researcher.

Thermal tests, which measured the resistance to high temperatures, showed an increase in their ability to withstand heat of 6.84%. This property is required to develop bio composites because industrial machines are used to melt the polymers adhered to the fibres.

In view of these positive results, more studies are set to be carried out, it is hoped that the advances will result in an additional income for the farmers, who will be able to process the fibres using special machines.