Use of Polymers and Its Classification - Coursework Example

Running Head: USES OF POLYMERS Uses of Polymers [The Writer’s Name] [The Name of the Institution] Uses of Polymers Introduction In the year 1827 a scientist by the name of Jons Jakob Berzelius coined the word polymer which he derived from the Greek words polys meaning many, and meros meaning parts. Humans have taken advantage of polymers for centuries in the form of oils, tars, resins, and gums. It was not until the industrial revolution that the modern polymer industry started to develop. Plastics under appropriate conditions of temperature and pressure can be moulded or shaped. Unlike rubbery materials plastics have a greater stiffness and lack reversible elasticity. Some plastics such as nylon and cellulose acetate are included in another type of polymers, but are still plastics even though they have been turned into a fibre. The people of the US consume about sixty million pounds of plastics every year. The two main types are thermoplastics and termosets. Thermoplastics soften on heating and harden on cooling. Thermosets flow on heating and form rigid material and does not soften on future heating. Thermoplastics are what are used mostly. Everyday plastics such as polyethylene and poly (vinyl chloride) have replaced traditional materials like paper and copper for a wide variety of applications. Polyethylene is used in a wide variety of applications because it can be produced in many different forms. The first of which is low-density polyethylene or branched polyethylene. This polymer has a large degree of branching; forcing the molecules to be packed rather loosely forming a low-density material. It is soft and pliable and has application ranging from plastic bags, containers, textiles, and electrical insulation, to coatings for packing materials. The opposite form of LDPE is HPDE or high-density polyethylene. The molecules in HPDE are tightly packed and are used in plastic tubing, bottles, and bottle caps. (Semlyen, 2000, 361-66) The two major classes of polymers are rubbery materials and plastics. The rubbery materials have a loose cross-linked structure. This causes rubber to possess memory. On average about 1 in 100 molecules are cross-linked. When the number reaches 1 in 30 the material becomes rigid and brittle. Natural rubber's repeating unit is isoprene. This material is found in the bark of the rubber tree and has been used by humans for centuries. Most of the rubber used today is a synthetic variety called styrene-butadiene rubber. (Doi, 1993, 119-24) Natural rubber played an important role in the creation of synthetic rubber because of isoprene's presence. Researchers eventually found success using butadiene and styrene with sodium metal as the initiator. This rubber was called Buna-S. Hundreds of Thousands of tons of synthetic rubber were produced in government controlled factories during World War 2. After which private companies took over and changed the name to styrene-butadiene rubber. Today the US alone consumes over a million tons of SBR each year. Rubber is an important part of most people's everyday life. Fibres are another form of polymers. Natural fibres such as cotton, wool, and silk are used by many and have been used by many for centuries. Man-made fibres such as nylon, polyester, rayon, and acrylic are also used by millions of people. The combinations of strength, weight, and durability have made these fibres a very important part of history. Nylon is used in parachutes and has a special property, which distinguishes it from other fibres, the fact that it has a degree of elasticity. Recently scientists have used polymers to grow artificial skin, and a group of scientists have recently grown a human ear under the skin of a lab rat. The study of polymers still continues and will continue for a long time to come. With every passing day brings the possibility of another outstanding breakthrough in the fascinating world of polymers. Polycarbonate is a polymer which also has many uses in today’s society. Polycarbonates are long-chain linear polyesters of carbonic acid and dihydric phenols, such as bisphenol-A. Polycarboante is formed when phosgene gas reacts with bisphenol-A (Burchard, 2003, 43-84). To fully understand the properties of polycarbonate, one must understand why the properties are the way they are. To the left is a diagram of the chemical structure of bisphenol-A. In this diagram two six-sided honeycomb shaped structures can be seen. These are called phenyl groups. Two groups labelled CH3 can also be seen. CH3 represents methyl groups. The presence of the phenyl groups on the molecular chain and the two methyl side groups contribute to molecular stiffness in the polycarbonate. The properties of polycarbonate are largely affected by the stiffness cause by this combination. This is done by first; the attraction between both of the phenyl groups between different molecules helps to ‘fix in place’ the individual molecules. (Wiberg, 1995, 69-77) The resulting occurrence is good thermal resistance but relatively high viscosity during processing. The inflexibility and the lack of mobility prevent polycarbonate from developing a significant crystalline structure. This lack of crystalline structure allows for light transparency. Polycarbonate is naturally transparent, nearly as transparent as glass. It has high strength, toughness, heat resistance, and excellent dimensional and colour stability. (Peacock, 2000, 89-99) Flame retardants can be added to polycarbonate without significant loss of properties. One of the biggest advantages of polycarbonate is its high impact strength. The diagram above compares the impact strength of polycarbonate to various other polymers (Paying particular attention to the variation between polycarbonate (PC) and Acrylic). Although this is an outstanding polymer for a variety of uses, it does have its disadvantages. It has only fair chemical resistance and is attacked by many organic solvents. It is also fairly expensive compared to other plastics. Some of the many uses of polycarbonate include being an ideal engineering plastic due to its ease of being moulded, blow moulded and extruded including having good electrical insulating properties. This means it is applied in electric meter housing and covers. As well as this polycarbonate is used as casket hardware, portable tool housings, safety helmets (due to its extremely high impact strength), computer parts and even vandal proof windows and bullet proof windows used in large bank safes. The price of polycarbonate makes it more suitable for application mainly in engineering. (Ramington, 1986, 22-26) Another big use of polycarbonate that hasn’t been mentioned is plastic lenses in sunglasses due to its high transparency and impact resistance. Acrylic refers to a family of synthetic polymers that contain one or more derivatives of acrylic acid. The most common of these is polymethyl methacrylate (PMMA). PMMA is a tough, highly transparent material giving it many similarities to polycarbonate which is why the two are in competition. Acrylic has excellent resistance to ultraviolet radiation and weathering. It can be coloured, moulded, cut, drilled, and formed. (Ivin, 1997, 55-59) Acrylic polymers are formed by the reaction of a monomer, the most common being methyl methacrylate with a catalyst. Organic Peroxide would be a typical catalyst. The catalyst provides the activation energy needed to start the polymerisation but does not become part of the polymer. The chemical structure of Acrylic can be seen in the diagram to the left. Acrylic, being nearly crystal clear is an excellent option for display cases. The thicker Acrylic material can shield against beta radiation. Acrylic is available in a wide array of forms and colours as well as being machineable and bendable. It can be used in a wide range of applications such as aquariums, picture frames, shelves and cabinets. Compared to polycarbonate, acrylic has a lot lower impact resistance, cannot be bullet-proof within a reasonable thickness, less bendable and formable and is harder to work with but on the other hand compared to acrylic, polycarbonate is more likely to scratch, the clarity isn’t as high, yellows after time due to the UV light whereas Acrylic doesn’t and is a lot more expensive. The facts presented have proved that there is no definite answer to which is better, Acrylic of Polycarbonate. (Moore, 2002, 217-23) The truth is both polymers are more suitable in the other depending on the various applications which they are being used for. Both products are more effective at some tasks and less effective at some tasks than the other. (Kaplan, 1993, 401-11) Plastics can be useful for many things in life. But sometimes they can be a nuisance because they are not naturally occurring and are made synthetically they take a very long time to decompose and will often stay in the environment for very long times. Some plastics cannot be recycled which will equate to more problems since they take a very long time to decompose already. Although plastics have many cons there are also many pros. Plastics such as glad wrap of cling wrap can keep out oxygen and moisture, which will prolong life of foods. Plastics that are non-reactant can be used as containers of foods because they do not react with any liquids. (Winter, 2006, 332-33) These plastics also replaced glass bottles which were much more expensive and took up much more room than plastics. In today's society many products are extremely over packaged. We can often find ourselves having to pay for the price of the package, which is included in the price of products. A clear example of over packaging is cheese slices. Each slice of cheese is wrapped in plastic and then all the slices are again wrapped in another layer of plastic; these give consumers an illusion that the product is much more hygienic. Plastics take a very long time to biodegrade and so they can remain in the environment for a very long time. Plastics can often get washed into the ocean where they will do the most damage. They can often get caught up with sea animals or be digested by the larger sea animals. Of the plastic wastes some end up in rubbish tips and dumps. Because the plastics are different they cannot be melded together and recycled. Also they take a long time to break down thus there are limited methods of disposing of the plastics. The plastics cannot all be easily burnt because, like nylon, they can release fumes, chemical which can have the possibility to be toxic. Having been stressed numerous times before, plastics cannot break down in the environment easily. This is because they are very molecularly stable. Scientists in recent times are trying to develop plastics that can react with the environment in order to break down. These plastics can react to such things as bacteria, soil, sunlight, water or certain temperatures. These plastics can be revolutionary in helping the environment and further developing plastics to become friendlier. Like compost they can be used very much the same way and be disposed of much more easily thus saving everyone more money, time and resources in order to recycle or dispose of the plastics properly. Plastics can be difficult to recycle because it is well known that different types of plastics cannot be melted together then reshaped to form new packaging or products. Although the melting and reshaping of plastics is possible it can be very laborious. Separating, cleaning and stripping of other materials from plastics are all required before an effective recycling method can be used on plastics. Although this method can be useful it can only work on thermoplastics because they are the only kind that can melt. Thermosetting plastics cannot be melted. But they can be ground up into powders or shredded. In conclusion plastics have changed our lives a great deal. Many things in today's world are made of plastic from Lego pieces to computer parts to aeroplane and car parts. Ever since plastics started they began to grow and improve. There is no doubt that in the future they will only continue to grow and improve. Plastic is something that the world would not be the same without. Plastic has become such an ordinary part of society that we hardly even notice it. Polymer chemistry deals with the development of plastics and has become such a vital part of chemistry. (Yamamoto, 2002, 299-307) Many synthetic fibres such as nylon and man-made rubber are also polymers. The extent to which these polymers affect our lives is amazing. Today plastics have replaced metals, natural fibres and hides, paper wood and stone and glass ceramics. Manufacturers use these plastics to make their products stronger, lighter, inexpensive and durable. Plastics' versatility is responsible for its many uses: everything from car parts to doll parts, from soft drink bottles to the refrigerators they get stored in. From the car you drive to work in to the television you watch when you get home, plastics help make your life easier and better. Plastic bottles mean we can actually lift an economy-size bottle of juice. And should we accidentally drop that bottle, it is shatter-resistant. Plastics also help to conserve energy in our homes. Vinyl siding and windows help cut energy consumption and lower our heating and cooling bills. Plastics have also replaced paper in packaging, wood and stone in making furniture etc. Plastics thus have become an integral and indispensable part of our lives. But, as useful they are, plastics do have disadvantages. The biggest problem is that most plastics take a very long time to decompose. Deciding how to dispose the plastic wastes has become a major environmental concern. As more and more plastic packaging materials are used by consumers, more plastic waste is generated. Since most plastics do not easily breakdown, this problem contributes significantly to environmental pollution. Plastics use up natural resources, consume energy to manufacture, create litter, choke marine life and add to landfill waste. There is a growing international movement to ban or discourage the use of plastic because of their environmental effects. Countries from Ireland to Australia are cracking down on the bags and action is stirring in the United States. Ooty too has banned the bags. The bottom line of this is that we cannot eliminate the monster of plastic which we ourselves have created. But we can definitely control and limit the use of plastic. References Burchard,W. Cyclic Polymers (Elsevier Applied Science, London, 2003), pp. 43–84. Doi, Y. K. Fukuda, Biodegradable Plastics and Polymers, Shinto Press, Osaka, Japan, 1993, 119-24 Ivin, K. J. J. C. Mol, Olefin Metathesis and Metathesis Polymerization (Academic Press, San Diego, 1997) 55-59 Kaplan, D. L. E. Thomas, C. Ching, Biodegradable Materials and Packaging (Technomic Press, Lancaster, PA, 1993), pp. 401–411. Moore, G. F. S. M. Saunders, Advances in Biodegradable Polymers (Rapra Review Reports, vol. 9, no. 2, 2002). 217-23 Peacock, A. J. Handbook of Polyethylene: Structure, Properties, and Applications (Marcel Dekker, New York, 2000). 89-99 Ramington, S. J. (1986). Industrial Plastics. The Goodheart-Willcox Company. 22-26 Semlyen, J. A. Cyclic Polymer (Kluwer Academic, Dordrecht, The Netherlands, ed. 2, 2000). 361-66 Wiberg, K. B. Oxidation in Organic Chemistry (Academic Press, New York, 1995). 69-77 Winter, Arthur. Organic Chemistry 1 for Dummies. (Wiley Publishing Inc, 2006). p. 332~333 Yamamoto, M. U. Witt, G. Skupin, D. Beimborn, R.-J. Muller, in Biopolymers Polyesters, A. Steinbüchel, Y. Doi, Eds. (Wiley-VCH, Weinheim, Germany, 2002), vol. 4, chap. 3, p. 299-307 Read More