TEACHING CHEMISTRY USING PRACTICAL PROJECTS; BIODEGRADABLE POLYMER FILMS FROM PECTIN

In order to encourage high school students to be interested in Chemistry, the Faculty of Chemistry (Universidad Nacional Autónoma de México, UNAM) has been working closely with several schools during the last years. A group of six students were involved in the 2014 term. The aim of the project was to study the feasibility of obtaining environment-friendly plastics from citric fruit materials. They did a literature search, with a constant supervision of their teachers at school, in order to find a biodegradable film material.

During the development of the assignment, they spent one day a week, throughout four months, at the University, under the surveillance of a Professor to perform the experiments and find the different variables involved in the process.

An advantage to such an approach is flexibility in learning new concepts and the formation of students with an incentive to choose a science career.

The specific raw materials chosen were oranges, they are abundant and available in Mexico all the year around; it's peel contains a large amount of polysaccharide, pectin, to be used as a raw material to obtain plastic films.

The initial step, was to extract pectin (a natural polysaccharide) from the orange's albedo (white part of the peel).

The process of extraction consists in several steps:
1.- Separation of the albedo from the orange's peel by mechanicals means.
2.- Vacuum drying.
3.- Hydrolysis with hydrochloric acid, to release the pectin from the albedo.
4.- Filtration of the soluble pectin.
5.- Recovery by ethanol precipitation, and drying in a vacuum oven.

Power dried pectin, was mixed with polyvinyl alcohol at various ratios, to achieve improvement in the physical properties. Furthermore, glycerine was added to the film as a plasticizer. Biodegradable flexible films were obtained from the extracted pectin.

The different samples of bioplastic films were characterized by infrared spectroscopy. Various types of films ranging, from rigid to flexible, were obtained with distinct formulations.

The most important aspect of this type of work, is the motivation of students to get involved actively in the use of science as a tool to protect environment, and find new green process alternatives.