Polymer Engineering
Introduction
Polymer engineering is a branch of engineering that involves the design, analysis, and modification of polymer materials. Polymers are large molecules composed of repeating subunits known as monomers, which are linked together by covalent bonds. The field of polymer engineering covers aspects of petrochemical industry, polymerization, structure and characterization of polymers, properties of polymers, compounding and processing of polymers and description of major polymers, structure property relations and applications.
History
The history of polymer engineering is intertwined with the history of polymer chemistry, a specialty that emerged in the 19th century with the discovery of rubber and the invention of vulcanization by Charles Goodyear. The development of plastics and synthetic fibers in the 20th century expanded the applications of polymers and led to the establishment of polymer engineering as a distinct field.
Polymerization
Polymerization is the process by which monomers are chemically bonded to form polymers. There are two main types of polymerization: addition (or chain-growth) polymerization and condensation (or step-growth) polymerization. In addition polymerization, monomers with unsaturated bonds are linked together by a chain reaction, while in condensation polymerization, monomers with two or more reactive groups react with each other to form polymers and a small molecule such as water or methanol.
Structure and Characterization of Polymers
The structure of a polymer is determined by the arrangement of its monomers and the chemical bonds between them. This structure can be characterized by various techniques, including spectroscopy, microscopy, and rheology. The characterization of polymers is crucial for understanding their properties and behavior, and for designing new polymer materials with desired characteristics.
Properties of Polymers
The properties of polymers depend on their structure and composition. These properties include mechanical properties such as strength, elasticity, and toughness, thermal properties such as melting point and glass transition temperature, electrical properties such as conductivity and dielectric constant, and optical properties such as refractive index and transparency. Polymers can also exhibit unique properties such as viscoelasticity, which is the combination of viscous and elastic behavior.
Compounding and Processing of Polymers
Compounding is the process of mixing polymers with additives to improve their properties or processing characteristics. Additives can include fillers, plasticizers, stabilizers, colorants, and flame retardants. Processing of polymers involves shaping them into useful products by various methods, including extrusion, injection molding, blow molding, thermoforming, and film blowing.
Major Polymers and Their Applications
There are many types of polymers, each with its own unique properties and applications. Some of the major polymers include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyethylene terephthalate, and poly(methyl methacrylate). These polymers are used in a wide range of applications, from packaging and construction to automotive and electronics.
Future Trends in Polymer Engineering
The field of polymer engineering is constantly evolving, with new developments in polymer synthesis, processing, and applications. One of the major trends is the increasing use of biopolymers and biodegradable polymers, driven by environmental concerns and sustainability goals. Other trends include the development of smart polymers, nanocomposites, and polymer-based energy storage devices.