In this type of polymerization, two molecules combine, causing the loss of a smaller molecule such as water, an alcohol or acid. Addition polymerization results in homochain polymers whereas condensation polymerization results in hetrochain polymers. These processes can occur in the gaseous, liquid and sometimes in the solid phase of the monomer. Words like ethylene dichloride and vcm are not typically used in daily conversation. The present work was performed to add to the knowledge of vcm emulsion polymerization.
The monomers used in addition polymerisation are alkenes or derivatives of alkenes. Typically, the monomers are fed to a reactor with or without a solvent. Lower yield per reactor volume, reduced reaction rate and average chain length necessity of selecting an inert solvent to eliminate the possibility of chain transfer used mainly for ionic polymerization and coordination polymerization. Here the covalent bonding occurs by an s n 2 reaction between a nucleophile, usually an amine, and a terminal epoxide. Temperature dependence of apparent solubility constant for nbutane in pvc. Ukraines pvc exports dropped by 6% to 119,400 tonnes. Find materials for this course in the pages linked along the left. Polymerization reactions to form pvc are the most important reactions from an industrial view see section 3.
Feb 19, 2014 this was a grade 12 chemistry project that i worked on. Pvc is a common, strong but lightweight plastic used in construction. Hope you guys enjoy, might be a bit on the fast side. In addition, in bulk polymerization, an apparatus for bulk polymerization is simple, reaction rate is fast, yield is high, highpurity polymers may be obtained, and polymers may be. The effect of temperature on molecular weight is a matter of polymerization kinetics and is. In the following example, the same bisphenol a intermediate used as a monomer for lexan serves as a. The two main types of polymerization are addition and condensation reactions. Polyvinyl chloridevinyl acetate2hydroxypropyl propenoate. The compound of alkenes and their derivatives are polymerized in the presence of a catalyst which is also known as the free radical generating initiator. Suppose we have a container full of ethene ethylene monomers and we unpair the pi electrons by a suitable method, either by appropriate radiation, or a free radical initiator. There are many forms of polymerization and different systems exist to categorize them.
Abs polymers can be given a range of properties, depending on the ratio of the monomeric constituents and the molecular level connectivity. B reaction is that used to make cocacola bottles i. Anshuman shrivastava, in introduction to plastics engineering, 2018. Suspension pvc accounts for more than 80% of the pvc market. The process for emulsion polymerization of vinyl chloride monomer vcm to produce polyvinyl chloride pvc has been used for decades, yet information concerning the monomer and the reaction mechanism has only recently begun to appear in the chemical literature. This reaction can be promoted by heat, pressure, and a chemical catalyst. Jul 10, 2014 describes the radical mechanism for making polymers from alkenes.
Even though the suspension polymerization of vinyl chloride has been extensively. Reduction of vinyl chloride monomer concentration in poly. It is important for stable polymerization to produce a uniformly mixed blend of monomer and polymer. Bulk pvc is used for specific types of hard sheets and bottles. When discussing the progress of step polymerization, it is not meaningful to use conversion of monomer as a measure because the reaction will still proceed even though all the monomer has been consumed. Any unreacted vcm is recovered through further separation, and recycled back into the process.
Vinyl chloride ch2chcl is most often obtained by reacting ethylene with oxygen and hydrogen chloride over a copper catalyst. Christopher wirthchristopher wirth introduction to polymersintroduction to polymers. The batch reaction of polyvinyl chloride pvc in a pressure auto. During polymerization, smaller molecules, called monomers or building blocks, are chemically combined to create larger molecules or a macromolecule. The bond lines extending at the ends in the formula of the product indicate that the structure extends for many units in each direction. This was a grade 12 chemistry project that i worked on. In chaingrowth or chain polymerization, the only chainextension reaction step is the addition of a monomer to a growing chain with an active center such as a free radical or ion. Emulsion pvc is primarily used for coating applications such as pvc coated fabrics. Polymerization is a reaction process in which two or more monomers are bonded chemically to form large polymer chains or threedimensional networks. You may be surprised to find out what two naturally occurring ingredients are the base for all vinyl compounds. Introduction to polyvinyl chloride downstream of the pvc industry the pvc converter industry pvc is supplied downstream to the pvc converter industries, where various additives including stabilizers and plasticizers are blended, of which are then converted by extrusion molding and calendering. Pdf kinetics and mechanism of bulk polymerization of. However, progressively higher hydrogen pressures are incapable of halting the polymerization reaction completely, but reduce the reaction rate by ca. In a step reaction polymerization reaction, sometimes called condensation polymerization, the polymer chains grow by reactions that occur between two molecular species.
Pdf polyvinyl chloride pvc is the third most commonly produced polymer and is important because of its mechanical characteristics. Polymer chemistry university of south carolina upstate. There are still, despite the huge commercial production of. Ratio of gc detector response areas for nbutane versus conversion of vcm at 60. Suppose we have a container full of ethene ethylene monomers and we unpair the pi electrons by a suitable method, either by appropriate radiation, or a. Step growth polymerization and condensation polymerization are two different concepts, not always identical. Christopher wirthchristopher wirth introduction to polymersintroduction to polymers ce435ce435. Describes the radical mechanism for making polymers from alkenes. An example is the polymerization reaction involving terephthalic acid and ethylene glycol, both of which are bifunctional. R t decreases at high conversion due to the trommsdorf effect, making the reaction hard to control. Graphenebased electrochemical sensors for biomolecules, 2019. Major industrial polymers major industrial polymers polyvinyl chloride pvc. Classification of polymerization reaction addition and. Major industrial polymers polyvinyl chloride pvc britannica.
All of the raw materials and water for this reaction must be fi ltered during production to ensure a quality end product. Viscosity increases as conversion increases, making heat removal and processing more difficult. Polymers include polyethylene, polypropylene, polyvinyl chloride pvc and polystyrene. In this unit we will look at those formed by the process of free radical polymerization. The manual adjustment of the vcm flow rate by means of. When the functionality of monomer is two bifunctional linear or straight chain polymer is formed.
Suspension polymerization of vinyl chloride and the processibility of. Vinyl chloride polymerization in microdroplet reactor core. The intermediate that carries the chain reaction during polymerization can also be a positive ion, or cation. Increasing pvc suspension polymerization productivity by using. The polymerization reaction in the reactor takes place by means of chaingrowth polymerization of vinyl chloride monomer vcm. Bulk and solution polymerization processes are characterized by the fact that the reactions proceed in a single phase. Heat released by the reaction is absorbed by the solvent, and so the reaction rate is reduced.
This paper is based on suspension polymerization method for pvc production. Degree of polymerization is a number, which indicates the number of repetitive units monomers present in the polymer. Chainreaction addition polymerization the polymerization can be represented by the reaction of a few monomer units. In this case, the cationic polymerization reaction is initiated by adding a strong acid to an alkene to form a carbocation. This cage reaction is substantial even in bulk polymerization at low conversion when the medium is essentially monomer. Pvc is one of the most extensively investigated and studied polymers. Mixing is facilitated as solvent reduces the rate of increase of the reaction medium.
After polymerization, pvc may be obtained without a drying process. Kinetics and mechanism of bulk polymerization of vinyl. Chlorinated polyvinyl chloride, cpvc, as it is called, is produced by chlorination of aqueous solution of suspension pvc particles followed by exposure to uv light which initiates the freeradical chlorination. Pvc one of the most used polymers, because it is easily processed and compounded, the raw materials involved in its formulation have a relative low cost and because a wide. To make the polyvinyl chloride pvc as per the requirements of the consumer market, many other additives are added into it. The reaction to make polypropylene h 2 cchch 3 is illustrated in the middle reaction of. Chain reaction polymerization, sometimes called addition polymerization, requires an initiator to start the growth of the reaction. Polymerization initiator an overview sciencedirect topics. Second only to pe in production and consumption, pvc is manufactured by bulk, solution, suspension, and emulsion polymerization of vinyl chloride monomer, using freeradical initiators. In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or threedimensional networks. This polymerization reaction may take place in pure monomer, in a solution, in a watermonomer emul sion or in a water suspension of monomer.
Vinyl chloride polymerizations are known to be autoaccelerating. The feasibility to reclaim the effluent for reuse in the pvc polymerization step of a pvc factory located in spain was demonstrated at pilot scale. Polymers can be formed by a variety of reaction pathways. Christopher wirthchristopher wirth introduction to. Vinyl chloride polymerization macsphere mcmaster university. At the reaction temperature, the initiator decomposes to form radicals that initiate the polymerization reactions. Polyvinyl chloride pvc is produced from vinyl chloride monomer vcm by a polymerization reaction. Experimental and theoretical evaluation of the reactions. It is made softer and more flexible by the addition of plasticizers. In this procedure, a monomer is dissolved in a nonreactive solvent that contains a catalyst.
The self reaction of these radicals is often the major pathway for the direct conversion of primary radicals to nonradical pro ducts in solution, bulk, or suspension polymerization. The reaction produces cpvc, which has thermal and chemical properties that are superior to pvc. Introduction to polyvinyl chloride downstream of the pvc industry the pvc converter industry pvc is supplied downstream to the pvc converter industries, where various additives including stabilizers and plasticizers are blended, of which are then converted by. Notice how every other carbon must have a chlorine attached. A good example is the freeradical polymerization of styrene, which is initiated by a free radical r that reacts with styrene. Pdf kinetics and mechanism of bulk polymerization of vinyl. Mar 31, 2017 the process for making pvc polyvinyl chloride is a mystery to most. Polyvinyl acetate produced industrially by the polymerization of vinyl acetate in bulk or solution processes. Polymers products that are commonly referred to as plastics by the general public are known to chemists as polymers. A polymer is a macromolecule which consists of small molecular units that are repeated over and over again to form a long chain. The ion produced in this reaction adds monomers to produce a growing polymer chain.
This article is a succinct description of the chemistry and technology involved in the production of polyvinyl chloride. If no plasticizers are added, it is known as upvc unplasticized polyvinyl chloride or rigid pvc. Once the growth of a chain is initiated by formation of an active center, chain propagation is usually rapid by addition of a sequence of monomers. The most common mode of the polymerization reaction, in this case, is the reaction governed by the free radicals. Polyvinyl chloride produced in bulk polymerization using monomer soluble free radical initiators. The largest family of polymers 3, vinyl polymers, are produced by chain polymerization reactions. Pdf ethylene polymerization reactions with zieglernatta. Mechanism of radical chain polymerization fundamental steps initiation, propagation, termination. Addition reactions with other halogens at the double bond, for instance, to yield 1,1,2trichloroethane or. Regnault in france first produced vinyl chloride monomer in 1835 and baumann first recorded its polymerisation in 1872 after exposing sealed tubes containing the monomer to sunlight. Solution polymerization is a method of industrial polymerization. In fact polyurethane polymerizes with addition polymerization because its polymerization produces no small molecules, but its reaction mechanism corresponds to a stepgrowth polymerization. Chemical engineering 160260 polymer science and engineering.
The reaction results in a polymer which is also soluble in the chosen solvent. Solution polymerization organic solvent or water solvent soluble monomer and initiator. Most of the homopolymers and copolymers of vinyl chloride, however, are produced by suspension polymerization. Table s1, showing the characteristics of the pvc samples, table s2, showing the mpw1k6. Polyvinyl chloride pvc, a synthetic resin made from the polymerization of vinyl chloride. Teknor apex has been an innovator in the pvc compound industry for more than six decades. The market share for emulsion pvc is approximately 10% and for bulk pvc, 5%. Article views are the countercompliant sum of full text article downloads since november 2008 both pdf and html across all institutions and individuals. Polymers with ahigh degree of polymerization are called high polymers and those with low degree of polymerization are called oligopolymers degree of polemerization dp.
Polymerization reactions are divided into two groups known as step reactions also called condensation reactions and chain reactions also known as addition reactions. These metrics are regularly updated to reflect usage leading up to the last few. Also, the relation between polymerization process and pvc dehydrochlorination is discussed and a new mechanism of its initiation based on the reactivity of. Polyvinyl chloride pipe fittings, clear film for meat packaging condensation polymerization and hydrolysis the chemical mechanism that cells use to make and break polymers are basically the same. The most significant difference is that in addition polymers there is no loss of atom. Addition polymerization and condensation polymerization addition polymerization. Since the termination reaction is retarded by the increase of the viscosity in the polymerization reaction, the polymerization sometimes proceeds rapidly by the gel effect into a runaway reaction. The molecules produced in a typical reaction vary in the number of carbon atoms in their chains. This method provides an effective tool not only for vinyl chloride polymerization kinetic studies but also can be adapted for use with other monomer and comonomer systems. Jan 21, 2016 pvc manufacturing methods using bulk polymerization do not use a heating medium such as water unlike suspension polymerization and emulsion polymerization, and polymerization thereof is performed using only a vinyl chloride monomer initiator and, as needed, a reaction additive. The process for making pvc polyvinyl chloride is a mystery to most. These polymers are then processed to make various kinds of plastic products. Chemical engineering 160260 polymer science and engineering lecture 6 mechanism and kinetics of free radical chain polymerization january 29, 2001.
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