Contribution to the development and physico-chemical characterization of cassava starch-based bioplastics reinforced with kaolinitic clay

Résumé

The fight against plastic pollution implies the development of polymers as alternatives to synthetic polymers. Starch is a natural polymer that can easily be plastified by means of additives. Yet, thermoplastic starch-based materials are chiefly identified by feable, mechanical properties and a high sensitivity to water. This work aims at elaborating and identifying cassava starch-based plastic films. They are reinforced with kaolin and processed with heat or not in order to be used as packaging. The physico-chemical characterisation of the starch reveals that starch is acid (pH=4.7), fine (diameter:19μm) and content 21.2% of amylose. It displays a small quantity of water and minerals. The monostructural characterisations show that the starch of cassava is of type C and the granulous are displayed in conical, elliptical and angular shapes. The physico-chemical characterisation of the kaolinitc clay highlights the presence of 75% of kaolinite, 11% of illite and 14% of quartz. The thermal processing of that kaolin at 700°C during one hour produces a metakaolin. The survey on plastic films developed with both kaolin and metakaolin testifies that metakaolin is a mineral filler which significantly improves the physico-chemical properties of plastic films. The metakaolin is then added to the different rates of masses (0; 5; 10; and 15 for 100g of starch) and to the mixture of starch and glycerol. The increase of the rate of metakaolin makes the plastic films become rigid by increasing the young's modulus and decreasing the lengthening of the breakage. The metakaolin induces some barriers effects at water intake and when emitting heat. All the plastic films are biodegradable items in the soil and on the soil surface. The rate 10% of metakaolin leads to a better compromise between both rigidity and deformation of the plastic films. Those plastic films may be used as packaging.

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