Aliphatic polymers polyurethanes

Nearly all of the polymers produced by step-growth polymerization contain heteroatoms and/or aromatic rings in the backbone. One exception is polymers produced from acyclic diene metathesis (ADMET) polymerization.22 Hydrocarbon polymers with carbon-carbon double bonds are readily produced using ADMET polymerization techniques. Polyesters, polycarbonates, polyamides, and polyurethanes can be produced from aliphatic monomers with appropriate functional groups (Fig. 1.1). In these aliphatic polymers, the concentration of the linking groups (ester, carbonate, amide, or urethane) in the backbone greatly influences the physical properties. 

A large number of polyurethanes were made of nitro aliphatic polymers consisting in co-polymerization of nitro aliphatic diisocyanate with nitro aliphatic... 

Hassan MK et al (2006) Biodegradable aliphatic thermoplastic polyurethane based on poly (epsilon-caprolactone) and L-lysine diisocyanate. J Polym Sci A Polym Chem 44 (9) 2990-3000... 

It is interesting to note that both polyurethanes derived from aliphatic diisocyanate and aromatic diisocyanate were degraded. With a few exceptions, the more rigid aromatic polymers degraded at slower rates than the aliphatic polymers. 

Linear aliphatic fluorinated polyurethanes have been tested with respect to the location of the fluorine atoms in the diol or diisocyanate component. Fluorine atoms introduced into the diisocyanate unit increase the stability of the urethane group, but the presence of these atoms in the diol unit favours dissociation of the urethane group to monomer. Comparison of PTFE and perfluoroamidine polymers shows that introduction of triazine rings in fluoromethylene chains enhances their stability. 

Chem. Descrip. Waterborne aliphatic polyester polyurethane polymer Uses Urethane for industrial wood, metal, and plastic coatings Features General purpose good adhesion to wide variety of substrates Properties Translucent dens. 8.8 Ib/gal vise. 125 cps pH 8.3 tens. str. 4000 psi elong. 200% (break) hardness (Sward) 70 VOC 261 g/l 35% solids 8.5% NMP Sancure 825 [Noveon]... 

Chem. Descrip. Waterborne aliphatic polyester polyurethane polymer Uses Urethane for coatings for rigid surfaces such as wood, concrete, plastic, and metal... 

Chem. Descrip. Waterborne aliphatic polyether polyurethane polymer Uses Urethane for textiles, thread, and leather finishes Features Soft designed to yield a stable froth without the addition of frothing additives... 

N-C-N- polyurethane elastomers, adhesives, and fibers. The aliphatic polymers melt 50 K below the decomposition temperature. Produced by phosgenation of amines. 

Attention in this section will be focussed on the thermoplastic polyurethane elastomers. These polymers are based on three monomers (1) an isocyanate source, (2) a macroglycol or carbonate, and (3) a chain extender, or curing agent. The isocyanates can be either aromatic or aliphatic. Although the aliphatic based polyurethanes are more expensive, and inferior in physical properties they do not show the embrittlement, weakening, and progressive darkening of the aromatic equivalents. 

In general, polyurethane urea are always created when diamines are used instead of diols as chain extenders during the synthesis of polyurethanes. This measure changes the hard segment of the resulting polymer molecule. The result is polyurethane urea instead of PUR. If aliphatic diisocyanates, macrodiols, and diamines are also involved, aliphatic polyurethane urea is created. If an aliphatic polyester (M = 1000 to 4000 mol) is used as the macrodiol, we speak of aliphatic polyester-polyurethane ureas [953]. 

Hassan, M.K., Mauritz, K.A., Storey, R.F., Wiggins, J.S. Biodegradable aliphatic thermoplastic polyurethane based on poly(E-caprolactone) and 1-lysine diisocyanate. J. Polym. Sci. A-Polym Chem. 44, 2990-3000 (2006)... 

Gabriel Rokicki is a chemistry professor at the Faculty of Chemistry, Warsaw University of Technology, Poland, where he received all his academic education (MSc in 1971, PhD in 1989, and tenure professor in 2002). His current scientific activities include synthesis, stmcture, and properties of polymer materials, such as aliphatic polycarbonates, polyurethanes, epoxy resins, and biodegradable polymers. He has devoted a special interest to the use of functional polymers in obtaining specialty ceramic materials as well as to polymer recycling. Earlier major interests included the utilization of carbon dioxide and cyclic carbonates in the synthesis of condensation polymers. Another topic of interest was polymeric ion-sensors based on modified calixarenes. He is the author and coauthor of 160 scientific papers and holds more than 50 patents in the above-mentioned areas. At the Faculty of Chemistry of Warsaw University of Technology, he conducts lectures on polymer chemistry and technology. 

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... 

Whilst the aliphatic nylons are generally classified as being impact resistant, they are affected by stress concentrators like sharp comers which may lead to brittle failures. Incorporation of mbbers which are not soluble in the nylons and hence form dispersions of rubber droplets in the polyamide matrix but which nevertheless can have some interaction between mbber and polyamide can be most effective. Materials described in the literature include the ethylene-propylene rubbers, ionomers (q.v.), polyurethanes, acrylates and methacrylates, ABS polymers and polyamides from dimer acid. 

As previously mentioned the initial research on polyurethanes was directed towards the preparation of fibre-forming polymers. Many poly hydroxy compounds and many di-isocyanates were used and the melting points of some of the more linear aliphatic polyurethanes produced cU"e given in Table 27.1. 

Telechelic polymers rank among the oldest designed precursors. The position of reactive groups at the ends of a sequence of repeating units makes it possible to incorporate various chemical structures into the network (polyether, polyester, polyamide, aliphatic, cycloaliphatic or aromatic hydrocarbon, etc.). The cross-linking density can be controlled by the length of precursor chain and functionality of the crosslinker, by molar ratio of functional groups, or by addition of a monofunctional component. Formation of elastically inactive loops is usually weak. Typical polyurethane systems composed of a macromolecular triol and a diisocyanate are statistically simple and when different theories listed above are... 

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. 

Isosorbide polyurethanes, especially those based on aliphatic isocyanates, may be useful in the same applications as conventional polyurethanes i.e. thermoplastics, coatings, and foams. In fact, excellent rigid foams have been obtained from P(I-MDI)(5). Isosorbide has a low melting point of 61°C and it is suitable for use in reactive injection molding processes alone or in the form of a mixture with other conventional diols. In addition, its polymers may also find specific applications due to the anticipated high complexation ability of the two tetrahydrofuran rings in their isosorbide units. 

TGA analysis shows that polymer degradation starts at about 235°C which corresponds to the temperature of decomposition of the cellobiose monomer (m.p. 239°C with decom.). Torsion Braid analysis and differential scanning calorimetry measurements show that this polymer is very rigid and does not exhibit any transition in the range of -100 to +250 C, e.g. the polymer decomposition occurs below any transition temperature. This result is expected since both of the monomers, cellobiose and MDI, have rigid molecules and because cellobiose units of the polymer form intermolecular hydrogen bondings. Cellobiose polyurethanes based on aliphatic diisocyanates, e.g. HMDI, are expected to be more flexible. 

Polyurethane-acrylic coatings with interpenetrating polymer networks (IPNs) were synthesized from a two-component polyurethane (PU) and an unsaturated urethane-modified acrylic copolymer. The two-component PU was prepared from hydroxyethylacrylate-butylmethacrylate copolymer with or without reacting with c-caprolactonc and cured with an aliphatic polyisocyanate. The unsaturated acrylic copolymer was made from the same hydroxy-functional acrylic copolymer modified with isocyanatoethyl methacrylate. IPNs were prepared simultaneously from the two-polymer systems at various ratios. The IPNs were characterized by their mechanical properties and glass transition temperatures. 

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