Condensation polymers polyurethanes

This process is not a condensation, because it does not involve the loss of a small molecule. Polyurethanes are technically addition polymers, but nevertheless, they are step-growth polymers because the growing polymer chain has two growth points rather than one. This example illustrates that step-growth polymers cannot always be classified as condensation polymers. Polyurethanes are used for insulation in the construction of homes and portable coolers. 

Uses. The largest uses of butanediol are internal consumption in manufacture of tetrahydrofuran and butyrolactone (145). The largest merchant uses are for poly(butylene terephthalate) resins (see Polyesters,thermoplastic) and in polyurethanes, both as a chain extender and as an ingredient in a hydroxyl-terminated polyester used as a macroglycol. Butanediol is also used as a solvent, as a monomer for vadous condensation polymers, and as an intermediate in the manufacture of other chemicals. 

Aromatic Isocyanates. In North America, aromatic isocyanates ate heavily used as monomers for addition and condensation polymers. The principal appflcafions include both flexible and rigid polyurethane foam and nonceUulat appflcations, such as coatings, adhesives, elastomers, and fibers. 

Synthetic resins form the heart of the paint industry. The tw o main types of synthetic resins are condensation polymers and addition polymers. Condensation polymers, formed by condensation of like or unlike molecules into a new, more complex compound, include polyesters, phenolics.. iniino resins, polyurethane, and epoxies. Addition polymers include polyvinyl acetate, polyvinyl chloride, and the acrylates,... 

Condensation polymers, which are also known as step growth polymers, are historically the oldest class of common synthetic polymers. Although superseded in terms of gross output by addition polymers, condensation polymers are still commonly used in a wide variety of applications examples include polyamides (nylons), polycarbonates, polyurethanes, and epoxy adhesives. Figure 1.9 outlines the basic reaction scheme for condensation polymerization. One or more different monomers can be incorporated into a condensation polymer. 

Figure 2.15 Reactions to produce typical condensation polymers a) polyester, b) polyamide with water as a byproduct, c) polyamide with HCI as a byproduct, d) polyurethane, and e) polyurea...

We report here that polyethylene adipate (PEA) and polycaprolactone (PCL) were degraded by Penicillium spp., and aliphatic and alicyclic polyesters,ester type polyurethanes, copolyesters composed of aliphatic and aromatic polyester (CPE) and copolyamide-esters (CPAE) were hydrolyzed by several lipases and an esterase. Concerning these water-insoluble condensation polymers, we noted that the melting points (Tm) had a effect on biodegradability. 

Using Carothers original classification, one would classify the polyurethanes as addition polymers, since the polymer has the same elemental composition as the sum of the monomers. However, the polyurethanes are structurally much more similar to the condensation polymers than to the addition polymers. The urethane linkage (—NH—CO—O—) has much in common with the ester (—CO—O—) and amide (—NH—CO—) linkages. 

To avoid the obviously incorrect classification of polyurethanes as well as of some other polymers as addition polymers, polymers have also been classified from a consideration of the chemical structure of the groups present in the polymer chains. Condensation polymers have been defined as those polymers whose repeating units are joined together by functional... 

Condensation polymers are prepared by reactions in which the monomeric units are joined by intermolecular elimination of small molecules such as water and alcohol. Among the most important kinds are polyesters and polyamides. Polyurethanes are addition polymers of acid derivatives. 

Problem 16.56 Indicate the reactions involved and show the structures of the following condensation polymers obtained from the indicated reactants (a) Nylon 66 from adipic acid and hexamethylene diamine (b) Nylon 6 from e-caprolactam (c) Dacron from methyl terephthalate and ethylene glycol (d) Glyptal from glycerol and terephthalic acid (e) polyurethane from diisocyanates and ethylene glycol. ... 

Phthalimidoglutaric acid (18), readily prepared from glutamic acid and phthalic anhydride, has served as a precursor for the preparation of several interesting condensation polymers (76MI1110l). For example, it is readily transformed (Scheme 7) into diisocyanate (19), which was utilized for the preparation of a number of optically active polyureas (by reaction with diamines), polyurethanes (by reaction with diols) and polyurea-urethanes (by reaction with amino alcohols). 

Interest in the photoconductive properties of the carbazole nucleus has also prompted studies concerned with its incorporation into condensation polymers. Examples of polymers prepared include polyamides (34), polyesters (35) and polyurethanes (36) (80MI11105). Thorough studies on the CT interactions of these polymers with the monomeric acceptor 2,4,7-trinitrofluorenone have been done. In all cases, the formation constant for the CT complex was higher with polymers than for monomeric models. At least two polymer... 

Much attention has been paid to the synthesis of fluorine-containing condensation polymers because of their unique properties (43) and different classes of polymers including polyethers, polyesters, polycarbonates, polyamides, polyurethanes, polyimides, polybenzimidazoles, and epoxy prepolymers containing pendent or backbone-incorporated bis-trifluoromethyl groups have been developed. These polymers exhibit promise as film formers, gas separation membranes, seals, soluble polymers, coatings, adhesives, and in other high temperature applications (103,104). Such polymers show increased solubility, glass-transition temperature, flame resistance, thermal stability, oxidation and environmental stability, decreased color, crystallinity, dielectric constant, and water absorption. 

Physical Stabilization Process. Cellular polystyrene, the outstanding example polytvinyl chloride) copolymers of styrene and acrylonitrile (SAN copolymers) and polyethylene can be manufactured by this process, Chemical Stabilization Processes. This method is more versatile and thus has been used successfully for more materials than the physical stabilization process. Chemical stabilization is more adaptable for condensation polymers than for vinyl polymers because of the fast yet controllable curing reactions and the absence of atmospheric inhibition. Foamed plastics produced by these processes include polyurethane foams, polyisocyanurates. and polyphenols. 

The synthesis of optically active polymers is an important area in macromolecular science, as they have a wide variety of potential applications, including the preparation of CSPs [31-37]. Many of the optically active polymers with or without binding to silica gel were used as CSPs and commercialized [38]. These synthetic polymers are classified into three groups according to the methods of polymerization (1) addition polymers, including vinyl, aldehyde, isocyanide, and acetylene polymers, (2) condensation polymers consisting of polyamides and polyurethanes, and (3) cross-linked gels (template polymerization). The art of the chiral resolution on these polymer-based CSPs is described herein. 

Most condensation polymers fall into one of four major categories the polyamides, polycarbonates, polyesters, and polyurethanes. One of the first and eventually most popular synthetic polymers to be synthesized was a polyamide called nylon 66, discovered in 1935 by the American chemist Wallace Carothers (1896-1937). Nylon 66 is made in the reaction between adipic acid (hexanedioic acid, HOOC(CH2)4COOH) and hexamethylenediamine (NH2(CH2)6NH2). The equation for that reaction is as follows ... 

Step-growth, or condensation, polymers are usually formed in a reaction between two monomers, each of which is at least difunctional. Polyesters, polyamides, polyurethanes, and epoxy resins are typical examples of step-growth polymers. These polymers grow by steps or leaps rather than one monomer unit at a time. 

Fig. 6.3 shows the empirical Yg values of the different series of condensation polymers characterised by their functional groups as a function of the number of the CH2 groups in the structural unit (Nch2)- It is evident that for all series, except the polyamides, polyurethanes and polyurea s, the slope of the lines is constant, viz. 2.7, the increment of the CH2 group (Fig. 6.3a). Only for the polymers mentioned - all containing hydrogen bonding groups - the slope is 4.3. Networks of inter-molecular hydrogen bonds obviously cause an apparent increase of the CH2 increment from 2.7 to 4.3 (Fig. 6.3b).

Condensation polymers result from formation of ester or amide linkages between difunctional molecules. Condensation polymerization usually proceeds by step-growth polymerization, in which any two monomer molecules may react to form a dimer, and dimers may condense to give tetramers, and so on. Each condensation is an individual step in the growth of the polymer, and there is no chain reaction. Many kinds of condensation polymers are known. We discuss the four most common types polyamides, polyesters, polycarbonates, and polyurethanes. 

Condensation polymers by the above delinition are usually produced by step-growth polymerizations but not all step-growth syntheses are condensation reactions. Thus there is no elimination product in polyurethane synthesis from a diol and a diisocyanate (cf. reaction (1-12)) ... 

Properties of fibers can be altered by carrying out interfacial polymerizations on their surfaces. Thus the shrink resistance of wool can be improved by immersing the fiber first in a solution containing one component of a condensation polymer and then immersing it in another solution containing theother component. Polyamides, polyurethanes, polyureas, and other polymers and copolymers may be grafted on wool in this manner. 

Polyurethane is a condensation polymer generally formed by the reaction between a di-isocyanate and a hydroxylated-terminated resin known as polyol in the presence of a catalyst and a foaming agent The urethane foam formed as a result of this reaction is a cellular polymer that derives its mechanical properties in part from the cell matrix formed during its manufacture and in part from the intrinsic polymer properties. Choice of the di-isocyanate and polyol dictates the inherent polymer properties in addition filler materials may be added to the polymer to improve its mechanical properties. 

Condensation polymers have been used although they are often not sufficiently hydrophilic enough to be considered within this entry. Typical polymers such as Nylon 6 and a typical polyurethane are shown (Figs. II and IJ). Some of these have been incorporated into composites with more hydrophilic materials Biopol, for example, is formed from a copolymer of a polyurethane and PEG. 

Polyesters, polyetherimide, melamine-formaldehyde, polyurethanes, polyurethane-ureas and polyamides (nylons) are examples of condensation polymers prepared by REX. " Because a small molecule is produced in condensation reactions, vent ports are employed. Between the ports are melt sealing screw sections, to prevent back mixing of volatilizing melt. Sealing screw sections are constructed by a right handed-left handed sequence of screw elements. Another chemistry feature of step-growth reactions is their sensitivity to errors in stoichiometric feed proportions. This poses problems with solid feed materials, which are normally converted to liquid form for more... 

Plastics with a carbonyl group can be converted to monomers by hydrolysis or glycolysis. Condensation polymers such as polyesters and nylons can be depolymerized to form monomers. For Polyurethanes (PURs), what is obtained is not the initial monomer, but a reaction product of the monomer diamine, which can be converted to diisocyanate. For PURs. hydrolysis is attractive as they can be easily broken down to polyols and diamines. The only issue is to separate them later. Steam-assisted hydrolysis has been shown to yield 60 to 80 percent recovery of polyols from PUR foam products. A twin screw extruder can be used as a reactor for hydrolysis. Glycolysis of PURS, yields mixture of polyols that can be reused directly. 

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