Recycling Plastics - Chemical Composition of Plastics - Case Study Example

Recycling Plastics Name Institution Affiliation Recycling plastics History of plastics The increased human consumption has led to the growth in the production of plastic and has eventually led to an increase of plastic waste produced. The increased concentration of plastic in the environment has resulted in adverse effects affecting human survival and the ecosystem. As people are becoming environmentally conscious, ways that the concentration of plastic can be reduced have imaged. One such way is the recycling of plastics. The paper will discuss the how the adverse effects from plastics can be reduced by limiting the amount of plastic waste. Understanding the history of plastic and their industry is important in developing a sustainable solution to the menace increased due to their concentration. The demand for a substitute to natural ivory in the mid-18th century created the motivation for innovation. In the year 1869, John Wesley Hyatt made the first known synthetic polymer (LaMantia, 2002). A New York firm was offering 10,000 dollars for the substitute. During the process, Wesley discovered that treating cellulose with camphor resulted in substance that could be designed to various shapes. He modified the substance to look similar to natural substances such as ivory and tortoiseshell. Plastics presented gains for both the environment and for financial growth during the time. The demand for poaching so as to use ivory in elephants' tusks scaled down as a cheaper substitute that is readily available emerged (LaMantia, 2002). The innovation also helped people developed economically by providing means of earning removing economic constraints nature had set. After the first discovery had been made, increased demand created by human activities led to the next step in the development of plastics. As electricity use became common in the United States, the demand for electric insulator that could substitute shellac increased. Trying to fill the gap, Leo Baekeland invented Bakelite in the year 1907 (LaMantia, 2002). It provided a better solution since it did not only act as an insulator but also was heat resistant and proved to be more durable. It also provided many alternatives due to its nature that saw it capable of being modified to fit various needs and purposes. Bakelite was the first fully synthetic plastic that did not contain molecule found in nature. The innovation led to the emergence of many companies that aimed at developing the use of polymers. They invested heavily in the research, and a variety of new products entered the market. The industrial revolution that occurred during and after World War (II) resulted in the increased demand for plastics (LaMantia, 2002). Industrial development was believed to be a show of might leading to increased growth of plastic industries. The declining natural resources and the high demand for plastic product further boosted the demand for other synthetic alternatives. Wallace Carothers invented Nylon in the year 1935 that was made up of synthetic silk (LaMantia, 2002). Increased military activities heightened the demand for plastic by 300 percent. Nylon was used in parachutes, body armor, among other military requirements (LaMantia, 2002). The economic recession that the United States experienced after the end of World War (II) demanded more economic activities (LaMantia, 2002). The availability of plastic at a low price and the modification capability to fit into various uses provided a platform for economic growth. Multiple uses of plastic had been discovered that provided cheaper alternatives to a variety of products. Such include replacing wood in furniture, steel in automobiles, and even glass in packaging. Chemical Composition of plastics The composition of plastics has been the basis of the various uses that have been derived out of plastics. The macromolecule structure of plastics is determined by the type of reaction involved. The reaction can be either polyaddition or poly polycondensation (EIRI Board of Consultants and Engineers, 2008). Polyaddition reaction can be as a chain reaction or as a step reaction. As a chain reaction, polyaddition involves the chemical combination of a large chain of monomer molecules enabled by exposing it to energy or by involving a catalyst. The combination can occur either by ring splitting or the aligning of the double bond. Either of the alternatives does not result in the loss of a hydrogen bond. Polyaddition produces thermoplastics types of plastics as a chain reaction. A step reaction occurs when the reaction does not involve the orientation of double bond. The reaction is such a reaction can occur when the hydrogen atoms change their position allowing the combination of the monomer molecules. The reaction can produce both thermoplastics and thermosets type of plastics. The other type of reaction leading to the formation of plastics, also known as polymers, involves polycondensation. The proliferation of compounds with multiple functions can result in the generation of plastics resulting in the release of water or ammonia molecules (EIRI Board of Consultants and Engineers, 2008). Both thermoplastics and thermosets type of plastics can be generated from the reaction. The basic molecules that form the monomer include carbon and hydrogen as the primary atoms (Manrich & Santos, 2009). Other common elements include oxygen, sulfur, and chlorine. The difference in the composition and their alignment justify the different types of plastics. The monomer structure determines the type of plastic to be produced. Plastic formed by the combination of ethylene monomers is known as polyethylene, propylene forms polypropylene, whereas vinyl chloride forms polyvinylchloride. Other monomers include caprolactam and tetrafluoroethylene resulting in the formation of polycaprolactam and polytetrafluorethylene respectively (EIRI Board of Consultants and Engineers, 2008). The atoms of the different elements are held together by valence bonds. The conformation that the plastic may adopt also determines its weight and the length. The structure may be linear, zigzag, helix, or even ball-shaped (Manrich & Santos, 2009). The difference in the conformation makes the various types of plastic have different length and weight. The forces that hold together atoms within the monomer structure are the primary valence bond and the secondary valence bond. The primary valence bonds determine the molecular structure, design, size, chemical type and the linkage with other molecules to form polymers (Manrich & Santos, 2009). Secondary valence bonds, on the other hand, influence the mechanical and thermal properties of the polymers as well as the formation of crystalline (Manrich & Santos, 2009). Classification of Plastics The different chemical structures of polymers determine the type of plastic to be formed. Plastics are classified into thermoplastics, elastomers, and thermosets (Manrich & Santos, 2009). The material structure of thermoplastics can either be linear or with branches whereas the elastomers are cross-linked with side chains. Thermosets, on the other hand, have a molecular structure that is strongly cross-linked. Examples of thermoplastic include polyvinylchloride, polyethylene, polycarbonate and polypropylene whereas elastomers include Butadiene-Elastomers and Elastomers Polyurethane (Manrich & Santos, 2009). Plastics classified as thermosets include Polyester Resins and Phenol Resins. Manufacture of plastics and the processes involved Plastics are made from products of petroleum and natural gas. Extraction of the hydrocarbons used to make plastics from refined oil and natural gas is the first process in the manufacture of plastic (Goodship, 2007). The extraction process results in the emission of greenhouse gases that have and adverse effect on the environment. The manufacturing process involves cracking and processing. Cracking involve heating hydrocarbon to extreme temperatures. The excessive heating enables the breakdown of large hydrocarbon molecules to smaller molecules. Monomers such as ethylene and propylene are extracted as a result of the cracking process. After cracking, the monomers go through the next phase of manufacturing known as processing. Multiple monomers are combined to form polymers (Goodship, 2007). The polymers are shaped into different shapes and sizes achieving the desired plastic resin. Once plastic resins are modified to the desired characteristics, they are converted into plastic by undergoing several additional processes such as extrusion blow molding and injection molding. Extrusion molding involves injecting molten polymer into the blow molding machine at a right angle. The molten polymer leaves the machine as a round shaped but hollow preform. Air is inserted through the seal of the hollow preform to design it into a desired shape. The shaped parison is then cooled allowing it to harden giving the desired product having been tested for possible leaks. Some of the plastics produced by the process include polypropylene and polyvinyl chloride. Injection molding is used to produce such plastics as nylon, polypropylene, and polyethylene. It differs from extrusion molding by using material to define the shape of the given plastic. Plastics in Packaging Plastics have been preferred the best for packaging due to the many advantages they provide. The ability of plastics to be molded into different types makes them favorable for packaging. Both manufacturers and consumers are hereby offered with various options to choose from depending on the intended purpose. The ability of plastics to be modified into rigid objects or flexible enhances them in playing their roles in offering protection and convenience respectively (Frane, 2014). They are also resistance to chemicals enabling their role in medical facilities. The major disadvantage of using plastics in packaging is their adverse effect on the environment. Their manufacturing process and their incapability to be decomposed make their use unsustainable. The manufacture of plastics from petroleum product and natural gas result in greenhouse emission that results in global warming (Goodship, 2007). A lot of campaign has been done to sensitize the threats posed by use of plastics on the environment by both governmental and non-governmental agencies. Companies that produce plastics and other bodies have responded by emphasizing the importance of recycling plastics so as to reduce these effects. Recycling plastics Increase in the amount of plastics waste has presented a challenge for the industries and innovators to devise ways to tackle the menace. It has presented a problem for through climate change, decline in world's resources and also energy consumption. The manufacture of plastics is based on utilizing scarce and non-renewable natural resources such as petroleum and natural gas (Knight, 2013). The ability to recycle and reuse plastics depends on the nature of given plastic. There are various methods that can be used to help reduce the effects posed by increased concentration of plastic waste. The three commonly forms of recycling include mechanical recycling, chemical recycling and thermal recycling (Knight, 2013). Mechanical recycling is done to generate raw material and other plastic products from the industrial plastic waste. The waste contains low level of dirt and the resins are well separated making it suitable for use as raw material for new products (Knight, 2013). The other recycling mechanism is through chemical recycling. It may involve several ways including monomerization, use of blast furnace, chemical feedstock or even gasification (Knight, 2013). Monomerization involves decomposing the waste chemically into their original monomers. The monomers are then used to reconstruct the plastic. Blast furnace feedstock recycling method includes the use of plastic waste as reducing agent in a reaction (Knight, 2013). The reaction is done at high temperatures in the absence of oxygen. The last form of chemical recycling is through gasification, which is conversion of plastic waste into gas. The gas is later used as a raw material for chemical industries. The end products of the recycling process include hydrocarbon, water, and carbon (IV) oxide. Liquefaction involves turning the waste back into oil that was used to generate it. Thermal recycling is the last common form of recycling. The waste is used in generating power through gasification, liquefaction or even forming solid fuel. Power is generated by gasification through converting the waste into gas that is later used to move steam turbine leading to power generation (Knight, 2013). The method is widely used in the country, and many nations across the world such as Japan, German, Holland and Sweden are adopting it (Knight, 2013). The choice of the recycling form by each country is dependent on various factors such as the cost involved, the guiding laws and the type of waste under consideration. Code numbers in plastic containers and their influence in recycling The difference in the types of plastics thus the type of recycle led the Society of the Plastic Industry to come up with a classification system that allowed consumers to identify the plastics (Frane, 2014). At the bottom of each plastic product, there is a triangle made up of three arrows. The sign means that it is possible to recycle the product. In the middle of the triangle, there is a number commonly known as the SPI code, meaning the Society of Plastic Industry code. Code one means that the plastic is Polyethylene Terephthalate and (PET, PETE) which is clear with good gas and moisture barrier (Frane, 2014). It is highly resistance to solvents and carbon (IV) oxide making it common for medicine jars, beverage bottles and food jars. Code two is high-density Polyethylene (HDPE) commonly known for its safety by offering protection against chemicals (Frane, 2014). The property makes it suitable for use in oil, foods and drinks at a household level. Other properties are that it is stronger when compared to other forms of polyethylene plastics and is highly resistance to solvents. Industries use the plastics in packaging of sensitive products such as detergents and other industrial chemicals. It is however highly recommended not to reuse the container made of high density polyethylene for food and drink if it did not contain such products originally. Products made of Polyvinyl chloride (PVC) have an SPI code number three. The material is used in all types of pipes and tiles due to its stable physical properties. It also has very stable electrical properties, excellent chemical resistance and highly resistant to chemicals (Frane, 2014). It is also used in insulating wires and cables and is also used for flexible packaging. Society of Product of the plastic industry (LDPE) code four is given to products made of Low-Density Polyethylene (Frane, 2014). The plastic is highly resistant to acids, base and even vegetable oils giving it multiple purposes. Some of the purposes include its use in packaging frozen foods, covering milk and other beverages, as container lids and in injection molding. Polypropylene plastic products are indicated by an SPI code number five in the middle of the triangle. The products have good chemical resistance to acids, alkalis and even most solvents (Frane, 2014). It also has a high melting point. The properties make it suitable for packaging hot liquids. It also has excellent optical clarity that enables its role in medicine bottles. Polystyrene plastics have low melting point and can be rigid or be foamed due to their versatility (Frane, 2014). Some of the properties include having an excellent moisture barrier, optical clarity, and low density. They form common food service items including plates, cups, trays and bowls. Other types of plastics made of other resins other than the ones listed are indicated by the code seven. The chemical and physical properties are dependent on the combination of resins, and the products are normally used for making gallons of reusable water (Frane, 2014). References EIRI Board of Consultants & Engineers. (2008). Plastic waste recycling technology. Delhi, India: Engineers India Research Institute. Frane, A. (2014). Collection & recycling of plastic waste. Place of publication not identified: Nordic Council Of Ministe. Goodship, V. (2007). Introduction to plastics recycling. Shawbury, UK: Smithers Rapra. Knight, G. (2013). Plastic pollution. London: Raintree. LaMantia, F. P. (2002). Handbook of Plastics Recycling. Rapa Technology. Manrich, S., & Santos, A. S. F. (2009). Plastic recycling. New York: Nova Science Publishers. Read More