Biodegradable Plastic Bags
Chapter 1
Introduction
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
Introduction
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