A plastic water bottle must be able to hold it shape, withstand high temperatures, must not absorb the water or release toxins, should be easy to clean and must be eco-friendly. To understand this, it is first necessary to define polymers, how they are made and the intermolecular forces that lead to polymers properties. Two polymers, Polylactic acid and polypropylene, will be explained to illustrate the connection between structure and properties. The differences and similarities will be explained, followed by the environmental and economic considerations. These factors will be used to show why Polylactic acid is preferable to other polymers for the production of water bottle.
A polymer is a long chain of molecules made up of many repeating identical units called monomers. A polymer made from two or more repeating units of monomers are called copolymers (Smith et al., 2006). Monomers are often made up of Hydrogen and Carbon with extra elements such as Oxygen, Nitrogen and Chlorine, creating the backbone of the polymer. These can be made synthetically, such as polyethylene or occur naturally like cellulose, as are the polymers being investigated are. Polylactic acid is made naturally and Polypropylene is made synthetically. Polymers can be three dimensional networks which don’t melt such as epoxy resin, and are called thermoset polymers, two dimensional or one dimensional networks or chains which can be melted such as polypropylene called thermoplastic polymers