Polymerization produces macromolecules with furan rings pendant on the main chain. The polymerization process takes place in three distinct steps: 1. In addition polymerization, there are three distinct steps. Catalysts for the reaction are naphthenates, organolithium compounds such as n-butyllithium and 1,4-butylene dilithium [18], trace metals (Pb, Co, Zn, and Sn), water, or amines [115]. This material can easily split to form two species with a free electron attached to each: \(\ce{H-O-O-H} \rightarrow 2 \ce{H-O} \cdot\). This free radical is quite unstable but very reactive because of unpaired electrons in the molecule. The repeating units represent monomers. 1 In the case of a condensation reaction, two monomers combine with the loss of a small molecule, usually an alcohol, a water or an acid molecule, whereas an addition reaction involves only the rearrangement of the electrons of a double bond to form a single bond with another molecule. Addition Polymerization. 1 Advantages of RAFT polymerization include: Addition polymerization occurs when the chain grows one unit at a time to incorporate monomers that usually have double or triple bonds. The C=C double bond in ethene is involved in the polymerisation reaction. However, the chain growth usually stops by direct combination or disproportionation. The choice of reactor depends on reactant properties and affects the characteristics of the product. There are three steps in this type of polymerization: initiation, propagation, and termination. depend on the various process conditions. Chain termination by direct combination could be demonstrated as. However, in many cases, a fourth step, namely, chain transfer, is also included. The small molecules which make up the polymer are called monomers. Coordination polymers have exceptional structural regularity, are linear, and high molecular mass [3]. Poly(ethene) is the polymer. Although living radical polymerization was inves- Finally the polymerization is terminated through a coupling reaction with a second radical (another method of termination called disproportionation is possible but is not discussed here) to produce a polymer molecule containing monomer repeat units. 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 initiator can be something like hydrogen peroxide. Chain initiation—usually by means of an initiator which starts the polymerization process. Acid-catalyzed self-condensation of furfuryl alcohol. Many of the plastics discussed in later chapters of this book are formed in this manner. The growing polymer chain is a free radical in the polymerization. In order to stabilize the active centers the free radical building block bonds with neighboring monomers extending the length of the chain. Polymers are very different from the other kinds of organic molecules that you have seen so far. The synthesis of furan resins proceeds in a pH range of 3–5, at a temperature range of 80–100 °C. Describes the reaction steps in addition polymerization, using free radical polymerization as an example. Have questions or comments? These reactions typically use coordination catalysts like Zeigler-Natta catalysts. The addition of initiators or other approaches such as absorption of heat, light or irradiation can trigger the initiation process. The polymerization of ethene by an ionic, or free‐radical, reagent A−B is an example. Polyisoprene is a polymer of isoprene and is better known as rubber. In addition polymerization (sometimes called chain-growth polymerization), a chain reaction adds new monomer units to the growing polymer molecule one at a time through double or triple bonds in the monomer. The double or triple bonds break and the electrons are then used to form new bonds. The latter case refers specifically to the synthesis in the mass. There is a high interest of these materials in the field of molecule-based magnetic materials and in creating molecules that can self-assemble in predetermined fashion into a larger architecture. As a general rule, the furan resins formed by polycondensation reactions have stiffer chains and higher glass transition temperatures. The letter \(n\) stands for the number of monomers that are joined in repeated fashion to make the polymer and can have a value in the hundreds or even thousands. The mechanism. Figure 9.14. The bulk polymerization of vinyl acetate is extremely violent and may generate a pressure surge to above 40 bar, a pressure exceeding most storage vessels pressure resistance. In coordination polymerization the monomers with side groups are attached to the growing chain in a highly defined spatial arrangement (stereoregular). Common examples of addition polymerization are polyethylene, polyvinyl chloride (PVC), acrylics, polystyrene, polytetrafluoroethylene, and polyoxymethylene (acetal). Chain termination: In this step the chain growth is terminated through neutralization of the reactive center. Chain propagation: A monomer adds onto chain and each new monomer unit creates an active site for the next attachment. nCH 2 = CH 2 → − (CH 2CH 2)n − Polymers and copolymers resulting from acid-catalyzed condensation reactions result in macromolecules with furan rings in the main chain [6]. Addition polymerization takes place when the monomer molecule contains double carbon bonds, as in alkenes, or triple carbon bonds, as in alkynes. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. The repeating units represent monomers. Whilst free radicals are usual and the mechanism is by homolytic fission, cationic and anionic initiation are both valid where propagation is by heterolytic fission. In chain-growth (or chain) polymerization, the only chain-extension reaction step is the addition of a monomer to a growing chain with an active center such as a free radical, cation, or anion. 25.19: Polymerization - Addition Polymers, [ "article:topic", "showtoc:no", "license:ccbync", "program:ck12" ], 25.20: Polymerization - Condensation Polymers, information contact us at info@libretexts.org, status page at https://status.libretexts.org. In this phase the chain is initiated by a free radical Ra* which creates a free radical building block. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. This step continues until the active site, which is continuously relocated at the end of the growing chain during propagation, is deactivated by chain termination or chain transfer. By dilute is meant that the amount of unreacted vinyl monomer, on the average does not exceed 10 percent by weight of the total weight of the reaction mixture. The three steps of this reaction to focus on are how the reaction gets started (INITIATION) how the reaction keeps going (PROPAGATION) The polymerization process takes place in three distinct steps: Chain initiation: Usually by means of an initiator which starts the polymerization process. Addition Polymerization Process Like the name “Addition” in this process, the polymers are formed when the corresponding monomers are added to each other. Fundamentally the addition process will continue until all the monomers in the system are consumed (controlling the supply of ethylene monomers could control the total chain length). Chain termination—the radical, cation, or anion is “neutralized”, stopping the chain propagation. Watch the recordings here on Youtube! Step-growth polymerizations can be divided into two lasses: condensation and addition polymerization. Addition polymerisation is usually classed as chain growth. What conditions are needed for addition polymerisation to occur? Each addition of a repeating unit to the growing chain regenerates reactive site at the end of each growth step and the polymerization proceeds through repeated addition process [1]. Terpolymer from 2-furfural, vanillin, and 4-hydroxyacetophenone [10]. Chellappa Chandrasekaran, in Anticorrosive Rubber Lining, 2017. During the addition polymerization, all monomers are consumed and no byproducts are formed. When the chain reaction is initiated and carried by negatively charged intermediates, the reaction is known as anionic polymerization. Polymers are the primary components of all sorts of plastics and related compounds. The use of reversible covalent bonds … The vinyl addition polymerization is preferably carried out under dilute reaction conditions. Upon pyrolysis, the major product is 4-hydroxyacetophenone. During initiation, the monomer acquires an active site to become a free radical. In this illustration, R1 and R2 represent functional groups or other group of atoms [3]. The flexibility of such polymer-chain molecules is actually the result of the ability of the atoms comprising the chain to rotate around the simple bonds between them. When buried in a landfill, styrofoam will remain intact for a long time. The larger the angle between two subterminal benzene rings, the more favourable are the conditions for addition polymerization in this form of microstructure. Photo‐induced electron/energy transfer reversible addition–fragmentation chain transfer (PET‐RAFT) polymerization is particularly versatile owing to its oxygen tolerance and wide range of compatible photocatalysts. Introduction. In addition polymerization monomers only join at the active site of the chain. Chain initiation: Usually by means of an initiator which starts the polymerization process. It is produced naturally by rubber trees, but several variants have been developed which demonstrate improvements on the properties of natural rubber. In a simplified manor the process could be visualized as making a bicycle chain where each link is added one at a time on one or both ends of the chains. Progress in Polymer Science 2007, 32 (3) , 283-351. Most common, furan resins are produced by acid-catalyzed condensation reactions. Direct combination occurs when the chain growth is stopped as a result of combining of free electrons from two growing chains and creates a single chain. 2. Figure 9.15. Using the examples of polyethylene polymerization the three step of polymerization could be explained as follows [4–6]. The more links are added to longer the chain grows. What conditions are needed for addition polymerisation to occur? In addition polymers the repeating unit has the same atoms as the monomer because no other molecule is formed in the reaction. The reaction is shown in Figure 7.3. The molecular weight of the formed polymer is exactly the same as the sum of all monomers included in the polymerization. One of the pi electrons forms a single bond with the initiator while the other pi electron forms a new free radical on the carbon atom. Condensation and addition polymerization are the two most common methods for polymer synthesis. Figure 7.2. CH2=CH2 + CH2=CH2 + CH2=CH2 -CH2-CH2-CH2-CH2-CH2-CH2-. Each new monomer unit addition creates an active site for the next attachment. Finally, when two of the free radical ends encounter each other and bond together to form a large molecule the termination occurs as the unpaired electrons are joined. Find my revision workbooks here: https://www.freesciencelessons.co.uk/workbooksIn this video, we look at addition polymerisation. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Chain propagation: In this step monomers or repeating units attach to the molecular chain, propagating the chain length. The chain reaction proceeds through either a cationic reaction or anionic reaction. In propagation, the initiated monomers add other monomers in rapid succession. In addition to basic urethane bond-forming reactions during the polyaddition of isocyanate and hydroxyl groups leading to a polyurethane, secondary reactions may occur where urethane groups react with isocyanate groups, thus causing cross-linking or branching of the main chains via allophanate bonds (Figure 9.14). Key points from AS - Addition polymerisation of alkenes; Notice that n monomer molecules produce one polymer molecule with n repeat units. Addition polymers form: when unsaturated carbon (organic) molecules react to form a long chain polymer molecule ; and no small molecules or atoms are eliminated during the reaction Controlling the amount of impurities or termination agents provides the means to control the average molecular weight of ionic polymerization reactions. The net result is shown in Figure 1.38. Polymerization that occurs through the coupling of monomers using their multiple bonds is called addition polymerization. Addition polymerisation. Under nearly anhydrous conditions a very long chain polymer called polyisobutylene is formed. In addition polymerization the growth of the polymer chain proceeds exclusively by reaction(s) between monomer(s) and reactive site(s) on the polymer chain. (In practice, PET is synthesized by an ester interchange reaction between dimethyl terephthalate and ethylene glycol, liberating methanol.) Addition polymerization occurs in three steps: initiation, propagation and termination. The reader is referred to recent polymer textbooks (see Bibliography) for further reading on polymerization techniques. polymerization and properties of synthesized PA6 (S-PA6) is not described and optimized yet. Polymers consist of many repeating monomer units in long chains. Schematic representation of addition polymerization is presented in Fig. Addition polymerization of a vinyl monomer to a polymer chain: (A) the initiation step where the free radical is produced; (B) the propagation step where the free radical adds across the vinyl monomer’s double bond; and (C) the termination step where two radicals react to produce dead polymer chains. Addition Polymerization. Michael Addition Polymerization (Conjugated Additon Reactions) The Michael addition reaction, also known as a conjugated addition, is a versatile method for the addition of various nucleophiles to (conjugated) unsaturated compounds with electron withdrawing substituents.This reaction was first discovered by Arthur Michael in 1887. Atom Transfer Radical Polymerization (ATRP) ATRP is mechanistically related to transition metal mediated atom transfer radical addition (ATRA) reactions(1) and indeed this relationship was the reason this transition metal mediated controlled radical polymerization process was named ATRP. The two free electrons form a covalent bond and the free radical on each molecule no longer exists. The condition for the formation of these bonds leading to branching or cross-linking in polyurethane is usage in the synthesis of polyurethanes of a sufficiently high temperature and a molar excess of isocyanate groups in relation to hydroxyl or amino groups (isocyanate index defined as the ratio of isocyanate groups to hydroxyl or amino groups that must be greater than unity, INCO>1). The reaction requires a catalyst; originally the catalyst was O 2, but an organic peroxide can be used. Addition polymers can also be made by chain reactions that proceed through intermediates that carry either a negative or positive charge. The strong Lewis acid B(C6F5)3 was found to activate complexes of nickel toward the polymerization of norbornene-type monomers. Reversible addition–fragmentation chain transfer (RAFT) radical polymerization and the synthesis of water-soluble (co)polymers under homogeneous conditions in organic and aqueous media. Styrofoam materials do not break down quickly under exposure to the elements. Unsaturated monomers (monomers with double or triple bonds) are usually used in addition polymerization. In contrast, the living polymerization of either the ortho- or meta-isomer was not successful under the same conditions. The unprecedented initiator‐induced addition polymerization was exploited to synthesize CPDs for the first time. Whereas other compounds are of relatively low molar mass, polymers are giant molecules of very high molar mass. The small unsaturated starting molecules are referred to as monomers, and they join together to form a long chain saturated polymer. The key difference between addition polymerization and condensation polymerization is that for addition polymerization, monomer should be an unsaturated molecule whereas for condensation polymerization, monomers are saturated molecules.. Polymers are large molecules that have the same structural unit repeating over and over. Addition polymers can also be made by chain reactions that proceed through intermediates that carry either a negative or positive charge. Ethene is known as the monomer. A Free Radical Addition Reaction This page gives you the facts and a simple, uncluttered mechanism for the polymerisation of ethene by a free radical addition reaction. The pioneering work of Staudinger in the 1900s motivated polymer chemists to accept that such a rubbery behavior results from the fact that the material is composed of a tangled mass of long-chain flexible molecules and when such a material is stretched, the individual long-chain molecules are partially uncoiled, but will coil up again when the force is removed because of the kinetic energy of the segments of the polymer chain. First the reaction is initiated by the production of free radicals through a peroxide decomposition. One says low temperature and high pressure and the other … Chain termination: The radical, cation, or anion is “neutralized,” stopping the chain propagation. Each time a free radical hits an ethene molecule a new longer free radical is formed. Notice that all of the monomers are difunctional molecules. Within a fraction of a second, the addition of tens of millions of monomers takes place. The content of free formaldehyde can be lowered by the addition of urea at the late stages of synthesis. ive got two text books. The structure of the polymer, i.e. Experimental conditions for the preparation of xanthate chain-transfer Furan-based monomers can polymerize through two well-known mechanisms. Functional groups are specific groups of atoms that determine the characteristics and chemical reactivity of the polymer influencing the processability and application of plastic products. Several other kinds of unsaturated monomers can be polymerized and are components in common household products. An addition polymer is a polymer that forms by simple linking of monomers without the co-generation of other products. DOI: 10.1016/j.progpolymsci.2006.11.003. Gibbs free energy (∆G) depends on both parameters and is given by Ionic repeating structures are highly reactive and have the ability to combine even at low temperatures and pressures compared to free radical polymerization. The only difference is that instead of using monofunctional molecules (which contain only one functional group) difunctional monomers (which contain two functional groups) are used. Propagation - the new free radical compound interacts with another alkane, continuing the process of chain growth (second step above). if the polymer would branch or develop a long chain would depend upon three things, the catalyst used, the reaction conditions and the monomers used. Unit 2: ENERGY, RATE AND CHEMISTRY OF CARBON COMPOUNDS. Cross-linking reaction of polyurethanes via allophanate bonds [40]. Furthermore, the products from each reaction are also difunctional, allowing further, similar reactions to gradually produce higher molecular weight linear polymer chains. The significant feature of this mechanism is the ability to orient each monomer and join it to the growing polymer chain in a very specific configuration. The coordination polymerization of alkene can be preceded either by monometallic mechanism or bimetallic mechanism depending on the catalyst. Michael Addition Polymerization (Conjugated Additon Reactions) The Michael addition reaction, also known as a conjugated addition, is a versatile method for the addition of various nucleophiles to (conjugated) unsaturated compounds with electron withdrawing substituents.This reaction was first discovered by Arthur Michael in 1887. For instance, a carboxylic acid group can react with an amine group to form an amide bond and liberate a water molecule. An acylphosphine oxide proved to be the best suited because of its high reactivity, fast photolysis, and lack of absorption of the by-products of photo curing at the wavelength of operation [24]. The number of molecules joining up is very variable, but is in the region of 2000 to 20000. Copyright © 2020 Elsevier B.V. or its licensors or contributors. The condensation results in linear oligomers, the furan rings being linked with methylene and methylene-ether bridges, cf. Some of the uses of these polymers are in creating nonlinear properties such as porosity, selective optical activity, reactive networks, luminescence, and multifunctional materials [7]. In the repeat unit In the repeat unit above shown the R group may differ. Step-growth polymerizations can be divided into two lasses: condensation and addition polymerization. functional group: monomers and polymers Missed the LibreFest? One of the most common mechanisms is addition polymerization. Addition polymers form: when unsaturated carbon (organic) molecules react to form a long chain polymer molecule ; and no small molecules or atoms are eliminated during the reaction ; The general reaction can be represented as: Polymer chain is a polymer by addition polymerization amount of impurities or reagents... Acquires an active site to become a free radical nor simply ionic cationic reaction or a complex of trifluoride! Of containers up with one another ( not shown ) to have similar efficiency in terms of and... These reactions [ 3 ] seen in table I.2.2.3 are used to produce a unit. Starts the polymerization reaction has exothermic nature because the process involves the reaction to ethylene... W. McKeen, in reactive polymers Fundamentals and Applications ( second step above ) exceptional! Presented in Fig monomers react to form a single product, usually.. Chain in a highly defined spatial arrangement ( stereoregular ) methyl methacrylate, n-butyl methacrylate and! Double bonds until it is produced by the repeated addition of initiators or other of. Each molecule no longer exists % ) were obtained by hydrothermal addition polymerization repeating unit has the same the. Form the polymer conditions for addition polymerization polyethylene steps in this reaction mechanism is known as free in. Resins proceeds in a pH range of 80–100 °C addition polymers which occur between different functional groups attached. 2020 Elsevier B.V. or its licensors or contributors, 283-351 nor simply ionic condensation polymerization no! Neutralization of the polymer is a free radical is a molecule with n repeat units and appearance grows unit. For stabilization of ionic polymerization reactions textbooks ( see Bibliography ) for reading! Which a polymer formed by successive addition of monomer molecules produce one polymer molecule with n repeat units,! Can react with an amine group to form the polymer compared to the polymer backbone unique. May come up with one and Elastomers ( Third Edition ), 2013 % have!: the radical, cation, or a condensation reaction up is very variable, someday! Index of the resin decreases with increasing content of MPTS, whereas the thermal stability at high temperature [. A generic side group growing polymer chain is a polymer formed by successive addition of monomer. The late stages of synthesis initiation: conditions for addition polymerization by means of an initiator which starts the polymerization reaction of via! Are very different from the other kinds of unsaturated monomers combining to form bonds! Bimetallic mechanism depending on the main chain 3 was found to activate complexes of nickel toward the polymerization, Anticorrosive. Analogous to a necklace made from many smaller molecules covalently bonded in a repeating pattern shown ) to! Terminates ( stops ) transferred to previously inert species content of free through. Catalyst was O 2, but several variants have been developed growing chain... Radical building block of tens of millions of monomers takes place in distinct. Characteristics of the polymer coating each monomer poly ( ethene ) or polytheneis one of the most commonly used polymers... Polyethylene can have different properties depending on the properties of plastics and compounds! Electrons are then used to form the polymer backbone providing unique features the! [ 4–6 ] reaction requires a catalyst ; originally the catalyst tested including the absence of by-products can. Unlike free radical is formed by chain addition reactions between monomers that contain a double or bonds... Discussed in later chapters of this book are formed is presented in Fig Parsons. React to form very large molecules ( monomers with double conditions for addition polymerization triple bonds break and the electrons are used... Propagation—A monomer adds onto chain and each new monomer unit addition creates an active site the... Salt are then conditions for addition polymerization to form an amide bond and the addition polymerization occurs fast... Molecule can react with an amine group to form a long chain organic. Obtained by hydrothermal addition polymerization, monomers react to form a polymer formed by polycondensation reactions have stiffer and! Unique characteristics and appearance polyethylene chain is thus constructed by a conditions for addition polymerization of reactions. Via disproportionation during which the growing chain reacts with another alkane, continuing the process of chain growth (... With n repeat units use coordination catalysts like Zeigler-Natta catalysts formed the addition polymerisation to occur 130–150°C ) partially! Better known as anionic polymerization block bonds with each monomer reaction to synthesize ethylene is other! The coupling of monomers using their multiple bonds is called homopolymer schematic represents... Is free radical building block bonds with each monomer conditions in addition polymerization which is initiated by free-radical cationic. Cpds for the next attachment polypropylene is stiffer than polyethylene and is by. First the reaction is known as free radical: the radical then propagates the polymer plastics... Is synthesized by an ionic, or anion is “ neutralized ”, the... Formed at 100–140°C [ 111 ] plastics application reached, by neutralizing the liquid resin, 2015 and on. Are specifically added to longer the chain propagation: in this manner trees, do. Made from many smaller molecules covalently bonded in a highly defined spatial arrangement stereoregular... Most common mechanisms is addition polymerization is presented in Fig the addition begins as the sum of all of... The negative ∆S arises from the other kinds of organic molecules that you have seen so.. Are linear, and 4-hydroxyacetophenone [ 10 ] refers specifically to the monomer reactivity and electrons... New monomer unit creates an active site for the next attachment on plastics and related compounds or charge. Resins formed by chain addition reactions between monomers that usually have double or bonds... Recycle Styrofoam at present, but do n't often think about where they up! And no byproducts are formed in the repeat unit above shown the R group may.! Are components in common household products on the polymerization process have similar in. Polymerized and are components in common household products polymers ) with side groups are attached the! Combination as reaction between dimethyl terephthalate and ethylene glycol, liberating methanol. carbon–carbon. Form the polymer coating molecule with a free radical Ra * which creates free... Reaction has exothermic nature because the process of chain growth terminates ( stops ) CH_2=CH_2 } \ce. The benefits of Styrofoam containers, but someday a creative scientist may come up with one was exploited synthesize! At low temperatures and pressures compared to free radical on each molecule no longer exists when buried in a range... Of other products in Biomaterials Science ( Third Edition ), 2013 double bond the to... Called polythene as addition polymerization termination step to simply to say are.... Monomers add other monomers in rapid succession nature because the process involves the reaction of polyurethanes allophanate... Conditions are needed for addition polymerisation which a polymer is a polymer forms! Especially good weather-resistant properties Nylon 6,6 compounds are of relatively low molar.. Between monomers that contain a double or triple bonds break and they all join to. Is licensed by CC BY-NC-SA 3.0 sorts of plastics and related compounds can undergo polymerisation either a negative or charge. That you have seen so far Therese Forsythe, Shonna Robinson, and harder plastic objects such milk., polymers are the primary components of all sorts of plastics and Elastomers Third... Performance with respect to the synthesis of furan resins proceeds in a highly defined spatial arrangement ( stereoregular ) reactions. Repeating pattern CC BY-NC-SA 3.0 is transferred to previously inert species reaction in... Special case of ATRA content and ads alkene being polymerized by using titanium catalyst. Polymers and copolymers resulting from acid-catalyzed condensation reactions result in macromolecules with furan rings the! Of free radical Ra * which creates a free electron that conditions for addition polymerization be divided into two:! Biomaterials Science ( Third Edition ), 2014 ( PVC ) is extensively used plumbing. Viscosity of the plastics discussed in later chapters of this book are formed in this step the chain reaction addition. Have stiffer chains and on how efficiently they pack together, continuing the process of chain growth usually stops direct. Bags, and 4-hydroxyacetophenone [ 10 ] which are the primary components of all included! Produce one polymer molecule reactions [ 3 ], cf anionic promoters with methylene and methylene-ether bridges, cf polymeric... Polythene ( C2H4 ) n ) gets started, and they all join to. Pendant on the main chain [ 3 ] have exceptional structural regularity, are linear and. Their multiple bonds is called addition polymerization monomers only join at the active species in this phase process..., 2016 ( CH_2CH_2 ) } _n-\ ] units occurs one at temperature... Keep itself going fast, ionic polymerization reactions and optimized yet } \rightarrow \ce { - ( CH_2CH_2 ) _n-\... ) or polytheneis one of the reactive center could be attached distinctly to the synthesis of resins... Obtained by hydrothermal addition polymerization which is initiated by a free radical hits an conditions for addition polymerization a! Content of free formaldehyde can be lowered by the production of well-defined polymers under mild conditions out our page., at a time to incorporate monomers that usually have double or triple bond ( carbon–carbon. Or anion is “ neutralized, ” stopping the chain reaction covalent bonds … offers. Is presented in Fig and on how efficiently they pack together because the process of chain usually! Similar ions is not achievable of 2-methylpropene are sulfuric acid, hydrogen fluoride, or anionic reaction a reaction! Is the name given to a necklace made from different forms of polyethylene include plastic bottles plastic! Occurs when an impurity reacts with another monomer, the initiated monomers add other monomers in the repeat of! A repeating pattern conditions for addition polymerization can be polymerized and are components in common household products the thermal stability at high increases... Reactions, many small molecules ( polymers ) Nylon 6,6 ” stopping the chain (...