| Starch & Starch Blends |
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Flexibiliser and plasticiser such as sorbitol and glycerine are added so that starch can also be processed thermo-plastically. By varying the amounts of these additives, the characteristic of the material can be tailored to specific needs (also called "thermo-plastical starch"). Thermo-plastical starch represents only one substance out of which starch-based bioplastics can be produced. The second fundamental component of the blends consists of water-repellent and biologically degradable polymers such as polyester, polyesteramids, polyesterurethanes or polyvinylalcohols. One plastic blend consists therefore of two phases: the continuous and hydrophobic polymer phase on one side and the disperse and hydrophilic starch phase on the other side. During the melting process in the extruder, the water soluble, disperse starch phase and the water-insoluble, continuous plastics phase bond together to form/produce a waterproof starch plastic. This cognition founded the basis for the further development and finally the break through of starch plastics (EP 0596437, EP 0799335). Starch blends and compounds are produced and developed individually for further use in the plastics processing industry, depending on and specific to their field of application. The existing production facilities allow the processing of foils, deep-drawn flat foils, die casting articles or coating out of starch granulates. Examples of this are carry bags, yogurt tubs, drinking cups, plant pots, cutlery, diaper foil, coated paper and cardboard. A chemical alteration (conversion to starch ester or starch ether with a high grade of substitution) can also modify starch thermo-plastically. This treatment is not yet overly widesprad or viable, due to the associated (high) cost.
(Sources: FNR, European Bioplastics) Bookmark this page!      |
Constituting
about 80 per cent of the bioplastics market, thermo-plastical starch currently represents
the most important and widely used bioplastic. Pure starch possesses the
characteristic of being able to absorb humidity and is thus being used for the
production of drug capsules in the pharmaceutical sector.
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