Averrhoa bilimbi: a natural coagulant for rubber latex

A U Nachiketh Kumar, Aman K A, India 16-18

Rubber plantations are popular all over the world. Farmers use formic acid to coagulate rubber latex, which is very corrosive. The solution released after the coagulation of rubber latex with formic acid remains acidic and makes the surrounding soil acidic when discharged. As a solution to this problem we tried an extract from Averrhoa bilimbi, commonly known as bilimbi, which produces a sour, tangy, juicy fruit. The fruit juice has a high concentration of oxalic acid, which is useful for cleaning and bleaching. It also contains acetic acid. A fruit weighing 20 g can produce approximately 10 ml of extract.

As formic acid has some limitations on rubber coagulation, bilimbi extract was used on rubber latex to get better-quality rubber sheets. The surface of latex particles are charged, which creates forces of repulsion between them that keep them from coagulating. In the coagulation process, formic acid neutralizes these charges, thereby eliminating the forces of repulsion between the particles. Bilimbi has oxalic acid with two replaceable hydrogen ions, compared to formic acid, which has only one replaceable hydrogen ion. Therefore, our aim is to prepare the natural coagulating agent from just bilimbi fruit extract to provide better quality and environmental advantages.

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