Biodegradable Plastic Bags

Topics: Starch, Bioplastic, Biodegradation Pages: 18 (4456 words) Published: March 14, 2012
Chapter 1

Background of the Study
Starch is a linear polymer (polysaccaride) made up of repeating glucose groups linked by glucosidic linkages in the 1-4 carbon positions. The length of the starch chains will vary with plant source but in general the average length is between 500 and 2 000 glucose units. There are two major molecules in starch - amylose and amylopectin. The alpha linkage of amylose starch allows it to be flexible and digestible. Starch-based biodegradable plastics may have starch contents ranging from 10% to greater than 90%.

Starch based polymers can be based on crops such as corn (maize), wheat or potatoes. Starch content needs to exceed 60% before significant material breakdown occurs. As the starch content is increased, the polymer composites become more biodegradable and leave less recalcitrant residues. Often, starch-based polymers are blended with high-performance polymers (e.g. aliphatic polyesters and polyvinyl alcohols) to achieve the necessary performance properties for different applications.

Starch may offer a substitute for petroleum based plastics. Starch is a renewable degradable carbohydrate biopolymer that can be purified from various sources by environmentally sound processes. Starch, by itself, has severe limitation due to its water solubility. Articles made from starch will swell and deform upon exposure to moisture.

To improve some of the properties, starch is often blended with hydrophobic polymers during the past decades by a number of researchers with petroleum polymers to increase biodegradability, and reduce the usage of petroleum polymer.

Biodegradation of starch based polymers is a result of enzymatic attack at the glucosidic linkages between the sugar groups leading to a reduction in chain length and the splitting off of sugar units (monosaccharides, disaccharides and oligosaccharides) that are readily utilised in biochemical pathways.

Biodegradable waste is an important substance due to its links with global warming. When it is disposed of in landfills, it breaks down under uncontrolled anaerobic conditions. This produces landfill gas which, if not harnessed, escapes into the atmosphere. Landfill gas contains methane, a more potent greenhouse gas than carbon dioxide. This can cause harmful effects on the environment. Substances that are broken down by biological processes are said to be biodegradable.

Glycerin is a viscid, colourless liquid of sp. gr. r 265 at 15° C., possessing a somewhat sweet taste; below o° C. it solidifies to a white crystalline mass, which melts at 17° C. When heated alone it partially volatilizes, but the greater part decomposes; under a pressure of 12 mm. of mercury it boils at 170° C. In an atmosphere of steam it distils without decomposition under ordinary barometric pressure. It dissolves readily in water and alcohol in all proportions, but is insoluble in ether. It possesses considerable solvent powers, whence it is employed for numerous purposes in pharmacy and the arts. Its viscid character, and its non-liability to dry and harden by exposure to air, also fit it for various other uses, such as lubrication, &c., whilst its peculiar physical characters, enabling it to blend with either aqueous or oily matters under certain circumstances, render it a useful ingredient in a large number of products of varied kinds. Objectives

General Objective:
To test the cornstarch and glycerin in providing a biodegradable polymer.Specific Objective:
To determine which of the treatments performed in the experimentation is more applicable in making Biodegradable polymers.

Significance of the Study
This study was conducted in order to make something more effective and useful to the world. Today, our world is undergoing and experiencing the global warming. Global warming and climate change are aspects of our environment that cannot be easily or quickly discounted. Many factions still...
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