ABSTRACT: BIOPLASTICS or organic plastics are a form of plastics derived from renewable biomass sources, such as vegetable oil, corn/pea starch, Microbiota. Kanjivellam is ‘Malayalam’ word for the water (vellum) drained from boiled rice (kanji). Rice water is the suspension of starch obtained by draining boiled rice. Here, starch is extracted from Kanjivellam & this starch-based bioplastic is compostable which can break down in either anaerobic or aerobic environments. Flexibiliser and Plasticizer such as sorbitol and glycerine are added to it to make Thermoplastic Starch. Penetrating water-repellent chemicals such as reactive silanes and siloxane resins are used to make it waterproof. Characteristics (strength, tensile) of the material can be tailored to specific needs by other chemical additives such as vinegar.
INTRODUCTION: Our bioplastic is derived from a renewable raw material like starch (extracted from kanjivellam or rice water). This rice water is very rich in starch which is the main ingredient of our plastic. It can be extracted by using drying agents like Sodium Sulphate, Magnesium Sulphate, Calcium Chloride. The bioplastics are not hazardous/toxic in production and decompose back into carbon dioxide, water, biomass etc. when composted. Biodegradable plastics combine the utility of plastics (lightweight, resistance, relative low cost) with the ability to completely and fully biodegrade.
STARCH- BASED BIOPLASTIC:
Thermoplastic starch currently represents the most widely used bioplastic, constituting about 50% of the bioplastics market. Pure starch is able to absorb humidity, and is thus a suitable material for the production of drug capsules by the pharmaceutical sector. Flexibiliser and plasticiser such as sorbitol and glycerine can also be added so the starch can also be processed thermo plastically. The characteristics of the resulting bioplastic (also called "thermo-plastical Bioplastic”) can be tailored to specific needs by adjusting the amounts of these additives. Starch-based bioplastics are often blended with biodegradable polyesters to produce starch/polycaprolactone or starch/Ecoflex blends. These blends are used for industrial applications and are also compostable.
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined by glycosidic bonds.It consists of two types of polymer molecules: the linear and helical Amylose and the branched Amylopectin. AMYLOSE This is a long straight-chain polymer. This is a very useful polymer as it would give strength to the plastic. AMYLOPECTIN This is branched. When starch is dried from an aqueous solution it forms a film due to hydrogen bonding between the chains. However, the AMYLOPECTIN inhibits the formation of the film, as it makes the plastic brittle. Reacting the starch with a chemical like vinegar breaks down the amylopectin, giving strength to our plastic. Imparting different properties:
1. Physical : Varying the quantity of vinegar accordingly can give different properties to the plastic
if less amount of vinegar is used, then the plastic obtained would be hard and stiff. if more amount of vinegar is used, then the plastic obtained would be tensile and flexible.
2. Chemical: The starch based bioplastic or Thermoplastic starch need to be waterproof. This water repelling property can be imparted by ‘Penetrating water-repellent chemicals’ – such as reactive silanes and siloxane.