Polyesters, Polyamides, and Polyurethanes

Polyethylene terephthalate (PET) (Table 5.3.13) is obtained either by polycondensation of ethylene glycol and terephthalic acid or by transesterification of terephthalic add dimethyl ester with ethylene glycol. The polymer has an unusually high melting point (260-270 °C) and very good mechanical properties. PET botdes and textile as well as industrial fiber applications are among the main applications of this polyester. 

Linear PUR fibers, textiles Crosslmked PUR coatings, foams, elastomers 

The industrially most relevant polycarbonate (PC) is formed by the reaction of the diol bisphenol A with diphenyl carbonate or phosgene. Formally, polycarbonates can be regarded as polyesters of the acid H2CO3. Polycarbonates are transparent and display good mecdianical and dielectric properties but are unstable against many organic solvents and strong bases. 

Linear polyurethanes (PUR) are formed in a polyaddition readion of diisocyanates [e.g. toluene diisocyanate (TDI) or methylene diphenyl diisocyanate (MDI)] and diols (e.g., 1,4-butanediol or 1,6-hexanediol). Crosslinldng is introduced by either the reaction of triisocyanates or the reaction of triols instead of the corresponding difimctional monomer. 

Topic 5.3.7 Important process options for the production of polymers 

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This type of adhesive is generally useful in the temperature range where the material is either leathery or mbbery, ie, between the glass-transition temperature and the melt temperature. Hot-melt adhesives are based on thermoplastic polymers that may be compounded or uncompounded ethylene—vinyl acetate copolymers, paraffin waxes, polypropylene, phenoxy resins, styrene—butadiene copolymers, ethylene—ethyl acrylate copolymers, and low, and low density polypropylene are used in the compounded state polyesters, polyamides, and polyurethanes are used in the mosdy uncompounded state. 

As already mentioned, there has been renewed interest for using carbohydrates as a source of chemicals since the 1980s with the development of the chemistry of furanic compounds, particularly for the preparation of nonpetroleum derived polymeric materials, such as polyesters, polyamides and polyurethanes.[17,19]... 

Scheme 12.1 Thermal scission of aliphatic polyester, polyamide and polyurethane through rearrangement of six or four atoms...

The use of Diels-Alder and platinum-catalyzed polyaddition reactions of vinylferrocene derivatives to prepare ferrocene-containing polycarbosilanes has also been described. " These reactions were also used to prepare materials with additional functional groups that led to ferrocene and silicon-containing polyesters, polyamides, and polyurethanes. Molecular weights varied in the range of 3,800-6,000 and products were liquids or elastomers. 

The hetero-chain polymers, notably the polyesters, polyamides and polyurethanes, can also act as a source of new monomers or oligomers by hydrolysis and alcoholysis. This recycling process (sometimes called... 

The second general pattern of polymerization is step-growth or condensation polymerization. While terminal alkenes are the most common monomers in chain-growth polymerization, bifunctional molecules are the characteristic monomers for step-growth polymerization. The polyester-, polyamide-, and polyurethane-forming reactions shown below are examples of step-growth polymerizations ... 

HMF is a suitable precursor for the synthesis of bifunctional furan monomers as summarized in Scheme 4. All these monomers can be used to prepare polycondensates by step-growth reactions with the other corresponding bifunc-tional monomers derived either from petrochemical precursors or from renewable resources. The polycondensates obtained, such as polyesters, polyamides, and polyurethanes, etc. have been characterized [107-113]. Scheme 5 shows another approach for the synthesis of bifunctional monomers through acid-catalyzed condensation of the corresponding mono-functional furan derivatives with an aldehyde... 

Another approach involves the use of difunctional telechelic polyolefins with ester, hydroxyl, and amine terminal groups. Telechelic polyolefins can be used to make polyesters, polyamides, and polyurethanes with low permeability to solvents and gases. 

Condensation polymer (See Step-growth polymer. Section 17.12, and Special Topic C in WileyPLUS) A polymer produced when bifunctional monomers (or potentially bifunctional monomers) react with each other through the intermolecular elimination of water or an alcohol. Polyesters, polyamides, and polyurethanes are all condensation polymers. 

Where a polymer has functional groups in the main chain, typical of polymerization by step-reaction chemistry or chain poljunerization of heterocyclic monomers, the fimctional groups in the chain are often the weakest and may nndergo reactions which do not produce radicals. Thermal degradation by random scission, without significant yield of volatiles is typical of polymers such as polyesters, polyamides, and polyurethanes, all of which undergo thermolysis by reaction at the functional groups (5). 

Sebastian Munoz-Guerra completed his Ph.D in Organic Chemistry in 1974 at the University of Seville. After postdoctoral work on crystal structure and morphology of non-conventional nylons, he initiated research on synthesis and characterization of bio-based polymers and copolymers. Since 1987, he is full Professor in Chemical Engineering at the Technical University of Catalonia in Barcelona. His current research is focussed on the development of polyesters, polyamides and polyurethanes derived from carbohydrates with special attention paid to industrial aromatic polyesters, as well as on modification of microbial biopolymers with therapeutic interest. He has authored more than 200 peer reviewed papers and several book chapters, and has been granted more than 15 patents on these issues. 

Table 5.3.13 Industrially relevant polyesters, polyamides, and polyurethanes.

The equipment used for melt making is not completely linked to extrusion machinery, since the used melt viscosity in this process is low compared to other spinning processes, in the range of less than 100 pa, eg, PP is used in an MFR rage of 125—3000 (230/2.16). Resins used in the melt blown process are characterized by the already mentioned low viscosity and still some elastic properties in order to be able to spin into filaments. There are no restrictions, so polyolefins, polyesters, polyamides and polyurethanes, as well as bitumen or cellulosic solutions, are possible to process via the melt blown process into filaments. Even high melting point polymers such as Polyphenylensulfid (PPS), Polysulfon (PSU) or even Polyetheretherketon... 

Most polyesters, polyamides, and polyurethanes are susceptible to hydrolysis with a consequent decrease in molecular weight. Aliphatic polymers often hydrolyze more rapidly than aromatic polymers. Once again, the lower molecular-weight materials are subject to biological attack. The hydrolysis itself may be part of enzymatic attack on the main chains. Some polyurethanes based on polyester polyols are easily... 

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