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Reactions, classification polymerization

In the last section we examined some of the categories into which polymers can be classified. Various aspects of molecular structure were used as the basis for classification in that section. Next we shall consider the chemical reactions that produce the molecules as a basis for classification. The objective of this discussion is simply to provide some orientation and to introduce some typical polymers. For this purpose a number of polymers may be classified as either addition or condensation polymers. Each of these classes of polymers are discussed in detail in Part II of this book, specifically Chaps. 5 and 6 for condensation and addition, respectively. Even though these categories are based on the reactions which produce the polymers, it should not be inferred that only two types of polymerization reactions exist. We have to start somewhere, and these two important categories are the usual place to begin. [Pg.13]

The U.S. rubber processing industry encompasses a wide variety of production activities ranging from polymerization reactions closely aligned with the chemical processing industry to the extrusion of automotive window sealing strips. The industry is regulated by seven Standard Industrial Classification (SIC) codes [1] ... [Pg.545]

Basie definitions of terms relating to polymerization reactions [1,2] and stereochemical definitions and notations relating to polymers [3] have been published, but no reference was made explieitly to reaetions involving the asymmetric synthesis of polymers. It is the aim of the present doeument to recommend classification and definitions relating to asymmetrie polymerizations that may produce optically active polymers. [Pg.73]

Basic classification and definitions of polymerization reactions (lUPAC Recommendations 1994), Pure Appl. Chem. 66, 2483-2486 (1994). Reprinted as Chapter 4, this edition. [Pg.462]

Basic Classifications and Definitions of Polymerization Reactions, Pure Appl. Chem. 66,... [Pg.33]

The proceeding classification of polymerization reactions concentrates essentially on the organic chemical character of the involved monomers... [Pg.1341]

It is easy to show that for small t values, Eq. (2.29) transforms to Eq. (2.28). However, it is interesting to follow the pattern of P(t) dependence for the full range of p, from which it can be seen this dependence looks like a kinetic curve with self-acceleration. Thus the phenomenon of selfacceleration, which is observed in some cases, may be treated as a consequence of a two-stage polymerization reaction if the rate constants of both stages have values of the same order. The reaction rate at the initiation stage can be limited by various factors, and in this case, classification of activators as direct or indirect becomes meaningless.41... [Pg.33]

ACGIH TLV TWA 2 mg(Al)/m3 DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE Moderately toxic by ingestion. Experimental teratogenic and reproductive effects. Mutation data reported. The dust is an irritant by ingestion, inhalation, and skin contact. Highly exothermic polymerization reactions with alkenes. Incompatible with nitrobenzenes or nitrobenzene + phenol. Highly exothermic reaction with water or steam produces toxic ftimes of HCl. See also ALUMINUM COMPOUNDS, CHLORIDES, and HYDROCHLORIC ACID. [Pg.45]

Carothers classification (condensation vs. addition) is primarily based on the composition or structure of polymers. The second classification (chainwise vs. stepwise) was proposed by P. J. Floiy, and is based on the kinetic scheme or mechanism governing the polymerization reactions. Step reactions are those in which the chain growth occurs in a slow, stepwise manner. Two monomer molecules react to form a dimer. The dimer can then react with another monomer to form a trimer, or with another dimer to form tetramer. Thus, the average molecular weight of the system increases slowly over a period of time. This is exemplified by the following polyesterification ... [Pg.565]

The formation of polymers from the monomers is known as polymerization reaction. When more than one basic unit forms the polymer, the process is also named copolymerization. The polymerization reactions can be classified into two main groups, addition polymerizations and condensation polymerizations (or polycondensations). For the addition polymerizations, the resulting polymer has the repeating unit with the same molecular formula as the monomer, and the molecular mass of the polymer is the sum of the molecular masses of all the monomer molecules. For the condensation polymerizations, the resulting polymer has the repeating unit with fewer atoms than that of the monomer or monomers, and the molecular mass of the polymer is less than the sum of molecular masses of the original monomer unit or units because small molecules are eliminated following this reaction. This classification is not adequate for the characterization of the polymer itself, because the same polymer can be formed by more than one type of reaction. For example, a polyamide can be formed by addition from a lactam or by condensation from an co-aminocarboxylic acid as shown below ... [Pg.4]

There are two fundamental polymerization mechanisms. Classically, they have been differentiated as addition polymerization and condensation polymerization. In the addition process, no by-product is evolved, as in the polymerization of vinyl chloride (see below) whereas in the condensation process, just as in various condensation reactions (e.g., esterification, etherification, amidation, etc.) of organic chemistry, a low-molecular-weight by-product (e.g., H2O, HCl, etc.) is evolved. Polymers formed by addition polymerization do so by the successive addition of unsaturated monomer units in a chain reaction promoted by the active center. Therefore, addition polymerization is called chain polymerization. Similarly, condensation polymerization is referred to as step polymerization since the polymers in this case are formed by stepwise, intermolecular condensation of reactive groups. (The terms condensation and step are commonly used synonymously, as we shall do in this book, and so are the terms addition and chain. However, as it will be shown later in this section, these terms cannot always be used synonymously. In fact, the condensation-addition classification is primarily applicable to the composition or structure of polymers, whereas the step-chain classification applies to the mechanism of polymerization reactions.)... [Pg.11]

A second major classification of polymers was proposed by Flory [1] in 1953. This is based on the kinetic mechanism of the polymerization reaction. Hory classifies polymerizations into two categories ... [Pg.9]

Definitions, chemical and physical properties, and general features of the most relevant catalyst types used in coordination polymerizations are described in Section 5.3, after the classification by type of monomers most frequently used and studied in this kind of polymerization reactions. [Pg.86]

As disciissed in Chapter 1, under a scheme proposed by Carothers, polymers are classified as addition or condensation polymers depending on the type of polymerization reaction involved in their synthesis. This classification scheme, however, does not permit a complete difierentiation between the two classes of polymers. A more complete but still oversimplified scheme that is still based on the dilTerent polymerization processes places polymers into three classes condensation, addition, and ring-opening polymers. This scheme reflects the stractures of the starting monomers. Probably the most general classification scheme is based on the polymerization mechanism involved in polymer synthesis. Under this scheme, polymerization processes are classified as step-reaction (condensation) or chain-reaction (addition) polymerization. In this chapter, we will discuss the different types of polymers based on the different polymerization mechanisms. [Pg.37]

Although these earlier definitions were based on the chain structure of the polymers, they were closely related, as just described, to the mode of formation as well. It soon became apparent that such a classification has serious shortcomings, as so-called polycondensates could result from addition polymerization reactions. For example, although Nylon 6 can be prepared by the polycondensation reaction of e-aminocaproic acid (Braun et al., 1984), it is now synthesized by the ring-opening addition polymerization of e-caprolactam (Sandler and Karo, 1992), and this process has a profound effect on the... [Pg.28]

The many ways to make polymers can be broken into two types of reactions based on the mechanisms of the polymerization, step and chain reactions (5). This reaction classification was termed condensation or addition reactions in the past but this archaic nomenclature is slowly dying away. The labels step and chain were developed for the two types of polymerizations by Flory and Mark (5, 6). All step reactions conduct the same stepwise reaction between all reactive entities in the reaction mixture. The... [Pg.801]

The three tables embody a certain classification of polymerization reactions similar to that of the much simpler division of ordinary gas reactions into mono-, bi- and tri-molecular. However, through the inevitable overlapping of the three component reactions described, the conditions prove more complex and the systematization of polymerization reactions is less simple. [Pg.320]

The present Report makes no pretence at covering the field in all its many facets. Only work related to copolymerization chemistry will be reported and that is taken from the scientific literature, ignoring multitudinous patents which have appeared. The Report is largely confined to addition polymerization processes, although the sharp demarcation between the traditional classifications of polymerization reactions is to some extent becoming blurred, particularly when attempts have been made to incorporate both non-polar and polar structural units within a polymer chain, as will be seen later. [Pg.106]


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See also in sourсe #XX -- [ Pg.2336 ]




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