1. Introduction
Polymeric materials play a functional role in every aspect of daily life, from clothing to infrastructure. Polymers differ greatly from other materials, such as ceramics or metals, based upon the types of bonding. Metals bond metallically, creating a sea of electrons, and ceramics generally bond ionically, strongly tying electrons to lattice points. Polymers bond covalently in carbon chains, which (in general) make their properties more variable due to the possibilities of arrangement in bond length, angle, and molecular configuration. Polymers, on average, tend to be more lightweight, have a greater range of colors, lower thermal and electrical conductivity, less brittleness, more resistance to acids, bases, and moisture, and higher dielectric strength than their ceramic or metallic counterparts, but with great range. This variety of properties leads to a variety of classifications, and therefore differing processing methods based on the classification of polymer.
2. Polymer Classifications
Polymer processing differs greatly based on the category of polymer within the system. Polymers can be classified by chemical composition, structure, or testing behavior (thermal or mechanical).
2.1. By Chemical Composition
Most polymers are organic molecules, based upon a repeating carbon skeleton, but can also include other elements within the chain, most often oxygen, nitrogen, or sulfur. The base unit of a polymer chain is known as a monomer, or mer. The composition of the monomer will greatly affect the properties exhibited. Monomers can either be natural or synthetically created. Examples of common monomers can be seen in Figures 1-4. Within the monomer, the electronegativity and bonding properties of the constituent e...
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spaced –CONH– amide groups. Nylon 6-6, or poly(hexamethylneadipamide), is composed of. two structural monomers (hexamethylendiamine (H2N(CH2)6NH2) and adipic acid. (HOOC(CH2)4COOH), whereas Nylon 6, or poly(6-caprolactam), is composed of a single structural unit (either 6-aminocaproic acid (H2N(CH2)4COOH) or caprolactam). Ultimately, the answer is yes.
The purpose of this experiment was to create a polymer by reacting a mixture of decanedioyl dichloride and dichloromethane with a mixture of water, 1,6-hexadiamine and sodium carbonate. Specifically, we created the polymer Nylon-6,10. Nylon-6,10 polymers are used in a vast majority of things we use in everyday life such as zippers, the bristles in brushes, and even car parts. This experiment was different from the industrial method of making nylon because that takes place at a much higher temperature. A polymer is a substance that has a structure made of similar or identical units bonded together. All polymerizations fall into two categories: step-growth and chain-growth (both of which we used to form our polymer). Step growth polymerization
The first term that I noted during the movie was Conductive Polymers. Conductive polymers are almost always organic meaning a large class of chemical compounds whose molecules contain carbon. These polymers have extended delocalized bonds which are bonds found in a molecule that do not belong to a single atom or covalent bond. They are conjugated systems of double bonds and in a aromatic systems. The conjugated systems are atoms covalently bonded with alternating single and double bonds. When the electrons are removed or added into the valence bands the electrical conductivity increases. The conductive polymer has a low conductivity until the electron is removed from the valence band called (p-doping) or (n-doping) until it becomes more conductive. The movement of the charges is what is responsible for electrical conductivity. These polymers are plastic which are organic polymers and with mechanical properties such as flexibility and elasticity.
STRUCTURE Kevlar Aramid Fiber is a synthetic (man-made) material known as Polymer. A polymer is a chain that is made up of many similar molecular groups, better known as ‘monomers’ that are bonded together. The ‘Monomers’ are made up of fourteen Carbon atoms, two Nitrogen atoms, two Oxygen atoms and ten Hydrogen atoms. A single Kevlar polymer chain could possibly have anywhere from one to five million monomers bonded together. A group of polymer chains can be organised together in a fiber.
Figures 3a-d show the effect of polymerization time on %GY (Fig. 3a) ; %GE (Fig. 3b); %TC (Fig. 3c) and %HP (Fig. 3d) at four different temperatures ( 50 0 ; 60 0 ; 70 0 and to 80 0C ). It is evident that , as the reaction time became longer , all polymer yield , except %GE , increased. The polymerization time corresponds to 180 min. brought about the maximum percentages for the positively dependence of polymer criteria.
Polysaccharides Polysaccharides are polymers composed of multiple subunits of monosaccharides (simple sugars). They are formed by condensation reaction, in the same way as disaccharides are formed, the difference stands in the larger number of monomer units which they are composed from . The number of monosacchardies composing the chain is variable, and there are two types of chains that can be formed: branched or unbranched. The chains may be folded, thus making them compact and therefore ideal for storage.
The synthesis of polymers starts with ethylene, (or ethene). Ethylene is obtained as a by-product of petrol refining from crude oil or by dehydration of ethanol. Ethylene molecules compose of two methylene units (CH2) linked together by a double carbon
Polymer-Polyethylene is partially crystalline as well as amorphous because it has crystalline and amorphous regions. Also it has linear chains so this is the simplest structure compared to a branched or network chain. This can be of an advantage to it over other types of materials as its good toughness and elongation makes it very significant in the engineering industry as it can be moulded or extruded into shape...
chains instead of hydrogen atoms. Cross-linking is another way in which the polymer can be made stronger. This involves ultraviolet radiation that bombards the polymer with electrons and formulates bonds between the molecular chains of the polymers. This is like linear polyethylene but different in that it is more impact resistant, and it has a much higher density. This allows it to be stored or be used with different chemicals that would normally cause the polymer to desolve.3 This can start to become a problem because as the polymer continues to become chemically enhanced. So the ways of dissolving and recycling the polymer become more difficult.
BIBLIOGRAPHY Advantages to Aluminum. http://www.kaiserextrusion.com/advantage.html. November 28, 2000. Aluminum Facts. http://www.epa.gov/seahome/housewaste/src/alum.htm. November,28 2000. Bowman, Kenneth A. World Book Encyclopedia. "Aluminum." Chicago: World Book, Inc., 1992. Cobb, Cathy. Creations of Fire. New York: Plenum Press, 1995 Geary, Don. The Welder's Bible. Pensilvania: Tab Books, 1993. Knapp PhD, Brian. Aluminum. Connecticut: Grolier, 1996. Newmark, Dr. Ann. Chemistry. London: Dorling Kindersley, 1993. Walker, John R. Modern Metalworking. Illinois: The Goodheart-Willcox Company, Inc., 1985.
The small molecules which form polymers are called monomers. In other words monomers are the building block of polymers. Hundreds and thousands of monomers combine together to form a large molecule of polymer. A polymer can be a three dimensional network ( repeating units linked together left and right, front and back, up and down)
Conductive polymer has been known to have poor process ability due to their physical and mechanical characteristics. In order to overcome this difficulty, it has to be treated with a conductive polymer.Such treatment with a conducting polymer reduces the surface resistivity to (1–104 Ω).”6”
I have spent so much time learning about design through the paradigm of materials but now I want to connect mechanical aspects to the knowledge I have already gained. I am particularly interested in the research done by Dr. Drew Nelson, Dr. Sheri Sheppard and Dr. Friedrich Prinz whose work most closely fits my interests. I am interested in doing research in mechanical design as influenced by material usage. I am also looking forward to taking courses such as Imperfections in Crystalline Solids, The Magic of Materials and Manufacturing, and Nanomaterials Synthesis and Applications for Mechanical Engineers to explore topics I have already studied, but from a mechanical engineering perspective. Stanford’s combination of rigor and creativity appeal to me. I have always enjoyed a challenge and get great satisfaction from expanding my knowledge. Coming from a Materials Science and Engineering background where I have performed well, both in academics and leadership, I know I can be an asset to and learn from the world-class Mechanical Engineering program at
There are many different polymers available depending upon the starting raw ingredients. There are several broad categories, each with numerous variations. The most common are known as polyester, vinyl ester, epoxy, phenolic, polyimide, polyamide, polypropylene, polyether ether ketone (PEEK), and others. The reinforcement materials are often fibers but can also be common ground minerals.
Polymers are some of the core factors that enable the continuation of life, which is both the natural and the synthetic ones. Over time since the beginning of life, natural polymers were the main supports to living things. Eventually, in line with human development, synthetic polymers has become a valuable addition to the available and usable polymers.