Thermoplastic polyurethanes extenders

In addition, polyester polyols are made by the reaction of caprolactone with diols. Poly(caprolactone diols) are used in the manufacture of thermoplastic polyurethane elastomers with improved hydrolytic stabiHty (22). The hydrolytic stabiHty of the poly(caprolactone diol)-derived TPUs is comparable to TPUs based on the more expensive long-chain diol adipates (23). Polyether/polyester polyol hybrids are synthesized from low molecular weight polyester diols, which are extended with propylene oxide. 

Singer S.M. and Allot M.T., Thermoplastic polyurethane elastomer based on a saturated hydroxyl terminated polyol, difunctional aromatic chain extender and 1,5-naphthalene diisocyanate, US Patent 5 599 874, 1997. 

Thermoplastic polyurethanes are normally processed in conventional plastic machines and when heated to above 120 to 150°C will soften and can be processed. By definition, this process can be repeated over and over. The TPU is supplied as a polymer chain extended to a suitable length with terminal groups that do not allow any further chain extension. 

Ho et al (1996) examined polyol or polysiloxane thermoplastic polyurethanes (TPUs) as modifiers in cresol-formaldehye novolac epoxy resins cured with phenolic novolac resin for computer-chip encapsulation. A stable sea-island dispersion of TPU particles was achieved by the epoxy ring-opening with isocyanate groups of the urethane prepolymer to form an oxazolidone. The flexural modulus was reduced by addition of TPU and also the Tg was increased due to the rigid oxazolidone structure. Mayadunne et al (1999) extended this work to a series of phenol- and naphthol-based aralkyl epoxy resins. 

Thermoplastic polyurethanes (TPU) are a versatile family of elastoplastic materials characterized by outstanding toughness and abrasion resistance. These materials are prepared from three principal reactants, a difunctional polyol, a difunctional chain extender and a diisocyanate in accordance with the following reaction ... 

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. 

Figure 6 24 DEA results for thermoplastic polyurethane films with various metals in the chain extender (a) comparison between c(f) and M"(f) spectra recorded at 25 ""C (b) M (f) plot for a polyurethane sample PU(Cu ) placed in a brass electrode capacitor. Isothermal scans were performed between -55 °C and 40 °C, in 5 ° increments. The progressive upshift of various relaxations with increasing temperature of the scan is a typical behavior. [Adapted from Kalogeras, I. M., Roussos, M., Vassilikou-Dova, A., Spanoudaki, A., Pissis, P, Savelyev, Yu. V., Shtompel, V. L, and Robota, L. P. (2005), Eur. Phys. J. E 18,467. Copyright 2005. With kind permission of Springer Science and Business Media.l...

The preparation of polyurethane aqueous dispersions can be accomplished in several ways. The procedure claimed to yield at present the highest quality products involves the reaction of an isocyanate-terminated prepolymer in a water-miscible solvent, e.g., acetone, with a diamine carboxylate or sulfonate. The resultant polyurethane ionomer solution is mixed with water which forms the dispersion and further chain-extends the polymer. Finally, the organic solvent is removed by distillation and can be recycled. As in the case of the thermoplastic polyurethane elastomer adhesives, dispersions can also be prepared with different degrees of crystallinity in the polyurethanes depending on the nature of the prepolymer. 

Hsu T-F and Lee Y-D (1999) Properties of thermoplastic polyurethane elastomers containing liquid crystalline chain extender (I) Synthesis and properties of hard segments, FnZj/mer 40 577-587. 

The viscoelastic properties of semi-IPNs based on a thermoplastic polyurethane (TPU) and a chemically crosslinked polyurethane (PU network) formed in the TPU solution, as well as of the same semi-IPNs filled with " (-Fe203 powder have been studied by Brovko et al. [27]. The TPU (molar mass 40000 g/mole) was synthesized from poly (1,4-butylene) glycol adipate (molar mass 1000 g/ mole), 4,4 -methylenebis(phenyl isocyanate) and 1,4-butane diol as a chain extender. The PU network was based on a vinyl chloride/vinyl acetate/vinyl alcohol terpolymer with an adduct of 1,1,1-trimethylolpropane and 2,4-toluene diisocyanate the appropriate for crosslinking NCO/OH ratio was chosen to be 0.55. The non-filled semi-IPNs exhibited only one situated between those of TPU and PU network. Therefore, the components of the semi-IPNs may be assumed to be compatible. It was found that the semi-IPNs filled with a small amount of >Fe20g (up to 1.4 vol%) exhibited one shifted toward higher... 

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