Polyvinyl Ethanoate Essay
Introduction
A polymer is a large molecule comprised of numerous smaller molecules. It is possible for these large molecules to be linear, moderately branched, or highly interconnected. In the latter case the structure progresses into a large three-dimensional complex. The small molecules that serve as the basic building blocks for these large molecules are known as monomers (See Figure 1.1). An example of the relationship between a monomer and polymer is the commercially important material polyvinylchloride, which is comprised of the monomer vinyl chloride. The repeat unit in the monomer generally corresponds to the monomer from which the polymer was made. As with any rule, there are exceptions. For example, polyvinylchloride is formally thought to be made up of vinyl alcohol (CH2CHOH) repeat units; but factually, there is no such monomer as vinyl alcohol. The suitable molecular unit exists in the tautomeric form, ethanal (CH3CHO). In order to make this polymer, it is required that polyvinyl ethanoate is firstly prepared from the monomer vinyl ethanoate, and then to hydrolyze the product to yield the polymeric alcohol.
The size of a polymer molecule can be determined in one of two ways: mass or by the number of repeat units within the molecule. This latter indicator of size is deemed the degree of polymerization. …show more content…
The relative molar mass of the polymer is thus the product of the relative molar mass of the repeat units and the degree of polymerization. It is difficult to set a clear cut boundary between polymer chemistry and the remaining chemistry. Typically, molecules of relative molar mass of at least 1000 or a degree of polymerization of at least 100 usually fall into the area of polymer chemistry. A large majority of polymers in commercial use are organic in nature, meaning they are rooted on covalent compounds of carbon. The other elements used in polymer chemistry most frequently include hydrogen, oxygen, chlorine, fluorine, phosphorous, and sulfur, which are all elements that are capable of forming covalent bonds with carbon.
Many of the substances we use in everyday life are made from polymer chains. There are two types of polymers: synthetic and natural. Synthetic polymers are synthesized inside the lab by scientist and engineers through a succession of chemical reactions and are obtained using petroleum oil. A few examples of synthetic polymers include nylon, polyethylene, Teflon, polyvinylchloride, and polypropylene. On the other hand, natural polymers take place in nature and can be extracted from places such as living creatures and plants. These sort of polymers are usually water-based. Silk, wool, DNA, cellulose and proteins are all examples of naturally occurring polymers.
Synthetic polymers have made various industrial impacts with their many applications, but have also shown to be harmful to the environment. Because of this, it will be very advantageous if through the merging of other polymers, we can produce a cutting-edge polymer that has applied uses and is also environmentally friendly. The purpose of this paper is to highlight the applications of popular synthetic polymers polyethylene, polyvinylchloride, and polystyrene and to explain how and why these polymers have such a widespread use in our world today.
Polyethylene
Polyethylene has one of the simplest molecular structures (Figure 2.1) and is an immense tonnage plastic material that was first commercially manufactured in 1939 to be used for electrical insulation. There has been confusion surrounding the nomenclature of this polymer. The IUPAC recommended name for the monomer is ethene making the IUPAC name for the polymer polyethene. However, this name is rarely used by chemists and engineers working with the material. Therefore, throughout this paper this polymer will be referred to as polyethylene, the more widespread name.
There are four distinct industrial routes to the construction of polyethylene which yield products that have moderately different properties. These four routes are:
(a) High Pressure Processes
(b) Ziegler Processes
(c) Phillips Process
(d) Standard Oil (Indiana) Process
The first group of these processes use pressures ranging from 1000 to 3000 atm and temperatures ranging from 80˚C to 300 ˚C. Free-radical initiators, such as benzoyl peroxide or oxygen, are normally used while conditions are carefully controlled in order to prevent a runaway reaction, which would form hydrogen, methane, and graphite instead of the expected polymer. High-pressure processes usually yield lower density polyethylenes, typically falling between the range 0.915-0.945 g cm-3, also having relatively low molar masses.
Ziegler processes are contingent on coordination reactions that are catalyzed by metal alkyl systems. Karl Ziegler of Germany discovered such a reaction and it was developed by G. Natta of Milan in the early 1950s, giving this process its name.
Titanium tetrachloride and triethylaluminium are parts of the complex a typical Ziegler-Natta catalyst is prepared from. This is fed into the reaction vessel before ethylene is added. This reaction takes place at low pressures and low temperatures, typically never exceeding 70˚C, with meticulous exclusion of air and moisture, which would result in the destruction of the catalyst. The polyethylenes created by such processes are of intermediate density, showing values of about 0.945 g cm -3. A range of relative molar masses may be acquired for such polymers by changing the ratio of the catalyst components or feeding a small amount of hydrogen into the reaction vessel.
Lastly, the Phillips and Standard Oil (Indiana) Processes create polyethylenes with high densities using fairly low pressures and temperatures. Below, Table 2.1 includes details of these processes.
Table 2.1 Details of Processes for Preparing Polyethylene
Process Catalyst Pressure/atm Temperature/˚C Density of product/ g cm-3
Phillips 5% CrO3 in finely divided silica/alumina 15-35 130-160 9.6
Standard Oil (Indiana) Supported MoO3 with Na, Ca metal or hydride promoters 40-80 230-270 9.6 Present-day, polyethylene is a very familiar material. It is a waxy solid which is fairly low in cost, easy to process, and displays superior chemical resistance. The disadvantage lies with the low relative molar mass grades due to the fact that they suffer from environmental stress cracking meaning they abruptly and catastrophically fail for no evident reason after having being exposed to sunlight or moisture. Despite this drawback, the various groups of polyethylene have a wide range of uses such as piping, packaging, and a component for chemical plants, crates, and items for electrical insulation. Applications of Polyethylene
Polyethylene is amongst the most common plastics produced in our world today. There is a wide variation of physical properties that his polymer comes in. Polyethylene can be firm and rigid or soft and elastic. To package and store a large variety of products, the packaging industry tend to go with soft and pliable films are often.
The low cost of polyethylene construction has motivated producers to prefer its use over many other plastics. Polyethylene provides the lowest softening point of the primary packaging plastics. The lower softening point contributes to lower processing energy costs. The three types of polyethylenes that are frequently used in the packaging industry are: High-Density Polyethylene, Low-Density Polyethylene, and Linear Low-Density Polyethylene. Detailed below are the different types of polyethylene and a few of its applications in the packaging industry.
(A) High-Density Polyethylene
High-density polyethylene has many advantages over many other polymers such as providing low cost, simple processing, and the ability to manufacture an opaque packaging product. Detailed below is a list of recurrent packaging products that use high-density polyethylene:
(i) Blown Mold Containers
Blown mold containers create common products that can be found in a regular household. Examples of these products include shampoo and oil bottles, cleaning bottles, blown mold drums, flower pots, and many more. Majority of blown containers are opaque in order to upgrade appearance and marketing appeal of a product. Clear HDPE containers commonly have a milky haze color similar to what is seen in Figure 2.2 to the left.
(ii) Extruded Packaging Films
High-density polyethylene extruded polymers also contribute to the making of many shopping bags. Grocery bags, packaging films, trash bags, and a large selection of retail packaging bags all fall under this category. High-density polyethylene provides exceptional puncture resistance, low stretch, reduced tearing, and moisture protection. High-Density Polyethylene film can come in a variety of thicknesses depending on the need but most high-density polyethylene extruded films are provided between 2 – 10 mils in thickness. (B) Low-Density Polyethylene and Linear Low-Density Polyethylene
Low-density polyethylene and linear low-density polyethylene are by far the most recurrent types of polyethylene when it comes to the manufacturing of packaging materials. Majority of packaging products are made with low-density polyethylene and linear low-density polyethylene. Their low production costs, extreme clarity, heat seal-ability, elongation, and softness are key reasons these forms of polyethylene are chosen more often for packaging. Detailed below are recurring packaging products that are widely used thanks to low-density polyethylene and linear low-density polyethylene.
(i) Extruded Packaging Films
The majority of stretch film is constructed using either blown or cast extruded linear low-density polyethylene.
Linear low-density polyethylene provides the high polyethylene shrink film the stretch rate required for stretch film. The majority of polyethylene bundling shrink films are created with low-density polyethylene. This is because low-density polyethylene offers a low shrink temperature along exceptional clarity. One of the most recognizable uses for polyethylene bundling film is for wrapping water bottles and canned goods. This is because polyethylene bundling film is much thicker and provides more strength than polyolefin or PVC shrink
film.
(ii) Packaging Bags and Tubing
Most stock poly bags used to wrap a large variety of products are made from low-density polyethylene. Many flat poly bags, Ziploc bags, and poly tubing derive from low-density polyethylene. The thickness of polyethylene bags usually range from 1 – 6 mils. The Flat poly bags and poly tubing can be closed using a heat sealer, staples, or tied using twist ties whereas the thicker poly bags are usually used to package nails, knives, and a variety of other sharp objects.
(iii) Injection and Blown Molded Containers
A portion of bottles and containers are made using low-density polyethylene and linear low-density polyethylene. The use of low-density polyethylene is common when the goal is to have a container with flexibility and clarity. The majority of squeezable bottles and containers use low-density polyethylene. An example of a container using low-density polyethylene is squeezable syrup bottles.
Polyvinylchloride
Polyvinylchloride is the widely accepted name for poly (1-chloroethene) and, in terms of international construction, is one of the three main polymers in current use, with the other two being polyethylene and polystyrene. Polyvinylchloride has many uses such as cable insulation, packaging, and toys. Polyvinylchloride has been shown to have a head-to-tail structure. Experimental evidence of this is that when dissolved in dioxin and treated with zinc dust, it goes through a Wurtz-type reaction yielding a product that contains a slight amount of chlorine and no obvious unsaturation. The alternate possible structure, the head-to-head organization, would yield unsaturated locations where adjacent chlorine atoms had been detached (See Figure 3.1).
A polymer is a large molecule comprised of numerous smaller molecules. It is possible for these large molecules to be linear, moderately branched, or highly interconnected. In the latter case the structure progresses into a large three-dimensional complex. The small molecules that serve as the basic building blocks for these large molecules are known as monomers (See Figure 1.1). An example of the relationship between a monomer and polymer is the commercially important material polyvinylchloride, which is comprised of the monomer vinyl chloride. The repeat unit in the monomer generally corresponds to the monomer from which the polymer was made. As with any rule, there are exceptions. For example, polyvinylchloride is formally thought to be made up of vinyl alcohol (CH2CHOH) repeat units; but factually, there is no such monomer as vinyl alcohol. The suitable molecular unit exists in the tautomeric form, ethanal (CH3CHO). In order to make this polymer, it is required that polyvinyl ethanoate is firstly prepared from the monomer vinyl ethanoate, and then to hydrolyze the product to yield the polymeric alcohol.
The size of a polymer molecule can be determined in one of two ways: mass or by the number of repeat units within the molecule. This latter indicator of size is deemed the degree of polymerization. …show more content…
The relative molar mass of the polymer is thus the product of the relative molar mass of the repeat units and the degree of polymerization. It is difficult to set a clear cut boundary between polymer chemistry and the remaining chemistry. Typically, molecules of relative molar mass of at least 1000 or a degree of polymerization of at least 100 usually fall into the area of polymer chemistry. A large majority of polymers in commercial use are organic in nature, meaning they are rooted on covalent compounds of carbon. The other elements used in polymer chemistry most frequently include hydrogen, oxygen, chlorine, fluorine, phosphorous, and sulfur, which are all elements that are capable of forming covalent bonds with carbon.
Many of the substances we use in everyday life are made from polymer chains. There are two types of polymers: synthetic and natural. Synthetic polymers are synthesized inside the lab by scientist and engineers through a succession of chemical reactions and are obtained using petroleum oil. A few examples of synthetic polymers include nylon, polyethylene, Teflon, polyvinylchloride, and polypropylene. On the other hand, natural polymers take place in nature and can be extracted from places such as living creatures and plants. These sort of polymers are usually water-based. Silk, wool, DNA, cellulose and proteins are all examples of naturally occurring polymers.
Synthetic polymers have made various industrial impacts with their many applications, but have also shown to be harmful to the environment. Because of this, it will be very advantageous if through the merging of other polymers, we can produce a cutting-edge polymer that has applied uses and is also environmentally friendly. The purpose of this paper is to highlight the applications of popular synthetic polymers polyethylene, polyvinylchloride, and polystyrene and to explain how and why these polymers have such a widespread use in our world today.
Polyethylene
Polyethylene has one of the simplest molecular structures (Figure 2.1) and is an immense tonnage plastic material that was first commercially manufactured in 1939 to be used for electrical insulation. There has been confusion surrounding the nomenclature of this polymer. The IUPAC recommended name for the monomer is ethene making the IUPAC name for the polymer polyethene. However, this name is rarely used by chemists and engineers working with the material. Therefore, throughout this paper this polymer will be referred to as polyethylene, the more widespread name.
There are four distinct industrial routes to the construction of polyethylene which yield products that have moderately different properties. These four routes are:
(a) High Pressure Processes
(b) Ziegler Processes
(c) Phillips Process
(d) Standard Oil (Indiana) Process
The first group of these processes use pressures ranging from 1000 to 3000 atm and temperatures ranging from 80˚C to 300 ˚C. Free-radical initiators, such as benzoyl peroxide or oxygen, are normally used while conditions are carefully controlled in order to prevent a runaway reaction, which would form hydrogen, methane, and graphite instead of the expected polymer. High-pressure processes usually yield lower density polyethylenes, typically falling between the range 0.915-0.945 g cm-3, also having relatively low molar masses.
Ziegler processes are contingent on coordination reactions that are catalyzed by metal alkyl systems. Karl Ziegler of Germany discovered such a reaction and it was developed by G. Natta of Milan in the early 1950s, giving this process its name.
Titanium tetrachloride and triethylaluminium are parts of the complex a typical Ziegler-Natta catalyst is prepared from. This is fed into the reaction vessel before ethylene is added. This reaction takes place at low pressures and low temperatures, typically never exceeding 70˚C, with meticulous exclusion of air and moisture, which would result in the destruction of the catalyst. The polyethylenes created by such processes are of intermediate density, showing values of about 0.945 g cm -3. A range of relative molar masses may be acquired for such polymers by changing the ratio of the catalyst components or feeding a small amount of hydrogen into the reaction vessel.
Lastly, the Phillips and Standard Oil (Indiana) Processes create polyethylenes with high densities using fairly low pressures and temperatures. Below, Table 2.1 includes details of these processes.
Table 2.1 Details of Processes for Preparing Polyethylene
Process Catalyst Pressure/atm Temperature/˚C Density of product/ g cm-3
Phillips 5% CrO3 in finely divided silica/alumina 15-35 130-160 9.6
Standard Oil (Indiana) Supported MoO3 with Na, Ca metal or hydride promoters 40-80 230-270 9.6 Present-day, polyethylene is a very familiar material. It is a waxy solid which is fairly low in cost, easy to process, and displays superior chemical resistance. The disadvantage lies with the low relative molar mass grades due to the fact that they suffer from environmental stress cracking meaning they abruptly and catastrophically fail for no evident reason after having being exposed to sunlight or moisture. Despite this drawback, the various groups of polyethylene have a wide range of uses such as piping, packaging, and a component for chemical plants, crates, and items for electrical insulation. Applications of Polyethylene
Polyethylene is amongst the most common plastics produced in our world today. There is a wide variation of physical properties that his polymer comes in. Polyethylene can be firm and rigid or soft and elastic. To package and store a large variety of products, the packaging industry tend to go with soft and pliable films are often.
The low cost of polyethylene construction has motivated producers to prefer its use over many other plastics. Polyethylene provides the lowest softening point of the primary packaging plastics. The lower softening point contributes to lower processing energy costs. The three types of polyethylenes that are frequently used in the packaging industry are: High-Density Polyethylene, Low-Density Polyethylene, and Linear Low-Density Polyethylene. Detailed below are the different types of polyethylene and a few of its applications in the packaging industry.
(A) High-Density Polyethylene
High-density polyethylene has many advantages over many other polymers such as providing low cost, simple processing, and the ability to manufacture an opaque packaging product. Detailed below is a list of recurrent packaging products that use high-density polyethylene:
(i) Blown Mold Containers
Blown mold containers create common products that can be found in a regular household. Examples of these products include shampoo and oil bottles, cleaning bottles, blown mold drums, flower pots, and many more. Majority of blown containers are opaque in order to upgrade appearance and marketing appeal of a product. Clear HDPE containers commonly have a milky haze color similar to what is seen in Figure 2.2 to the left.
(ii) Extruded Packaging Films
High-density polyethylene extruded polymers also contribute to the making of many shopping bags. Grocery bags, packaging films, trash bags, and a large selection of retail packaging bags all fall under this category. High-density polyethylene provides exceptional puncture resistance, low stretch, reduced tearing, and moisture protection. High-Density Polyethylene film can come in a variety of thicknesses depending on the need but most high-density polyethylene extruded films are provided between 2 – 10 mils in thickness. (B) Low-Density Polyethylene and Linear Low-Density Polyethylene
Low-density polyethylene and linear low-density polyethylene are by far the most recurrent types of polyethylene when it comes to the manufacturing of packaging materials. Majority of packaging products are made with low-density polyethylene and linear low-density polyethylene. Their low production costs, extreme clarity, heat seal-ability, elongation, and softness are key reasons these forms of polyethylene are chosen more often for packaging. Detailed below are recurring packaging products that are widely used thanks to low-density polyethylene and linear low-density polyethylene.
(i) Extruded Packaging Films
The majority of stretch film is constructed using either blown or cast extruded linear low-density polyethylene.
Linear low-density polyethylene provides the high polyethylene shrink film the stretch rate required for stretch film. The majority of polyethylene bundling shrink films are created with low-density polyethylene. This is because low-density polyethylene offers a low shrink temperature along exceptional clarity. One of the most recognizable uses for polyethylene bundling film is for wrapping water bottles and canned goods. This is because polyethylene bundling film is much thicker and provides more strength than polyolefin or PVC shrink
film.
(ii) Packaging Bags and Tubing
Most stock poly bags used to wrap a large variety of products are made from low-density polyethylene. Many flat poly bags, Ziploc bags, and poly tubing derive from low-density polyethylene. The thickness of polyethylene bags usually range from 1 – 6 mils. The Flat poly bags and poly tubing can be closed using a heat sealer, staples, or tied using twist ties whereas the thicker poly bags are usually used to package nails, knives, and a variety of other sharp objects.
(iii) Injection and Blown Molded Containers
A portion of bottles and containers are made using low-density polyethylene and linear low-density polyethylene. The use of low-density polyethylene is common when the goal is to have a container with flexibility and clarity. The majority of squeezable bottles and containers use low-density polyethylene. An example of a container using low-density polyethylene is squeezable syrup bottles.
Polyvinylchloride
Polyvinylchloride is the widely accepted name for poly (1-chloroethene) and, in terms of international construction, is one of the three main polymers in current use, with the other two being polyethylene and polystyrene. Polyvinylchloride has many uses such as cable insulation, packaging, and toys. Polyvinylchloride has been shown to have a head-to-tail structure. Experimental evidence of this is that when dissolved in dioxin and treated with zinc dust, it goes through a Wurtz-type reaction yielding a product that contains a slight amount of chlorine and no obvious unsaturation. The alternate possible structure, the head-to-head organization, would yield unsaturated locations where adjacent chlorine atoms had been detached (See Figure 3.1).