Study the removal of fluoride from water by using chitin

Abstract

Polymer is a large molecule (molecular weight ~10 000 or greater) composed of many smaller molecules (monomer) covalently bonded together. While the term polymer in popular usage suggests "plastic", polymers comprise a large class of natural and synthetic materials with a variety of properties purposes.Single polymer molecules typically have molecular weights between 10,000 and 1,000,000 g/mol--that can be more than 2000 repeating units depending on the polymer structure! The mechanical properties of a polymer are significantly affected by the molecular weight, with better engineering properties at higher molecular weights. The softening point (glass transition temperature) and the melting point of a polymer will determine which applications it will be suitable for. These temperatures usually determine the upper limit for which a polymer can be used. For example, many industrially polymers have glass transition temperatures near the boiling point of water (1000C, 212F), and they are most useful for room temperature applications. Some specially engineered polymers can withstand temperatures as high as 3000 C (572 F). Higher molecular weights. Polymers can be crystalline or amorphous, but they usually have a combination of crystalline and amorphous structures (semi-crystalline). The polymer chains can be free to slide past one another (thermoplastic) or they can be connected to each other with cross links (thermosets or elastomer). Thermoplastics can be reformed and recycled, while thermosets and elastomers are not rework able. The chemical structure of the chains also has a tremendous effect on the properties. Depending on the structure the polymer may be hydrophilic or hydrophobic (likes or hates water), stiff or flexible, crystalline or amorphous, reactive or uncreative.