Chemical structures aliphatic isocyanates

Lights stability of polyurethanes depends to a large extent on their chemical structure, and both components (Le., isocyanate and polyol) have an influence. Polyurethanes based on aliphatic isocyanates and polyester diols show the best light stability if yellowing is considered, whereas polyurethanes based on aromatic isocyanates and polyether diols are worst in this respect. 

The structures of the thermal degradation products obtained in the DPMS of PC/Ny6 blend permitted the identification of the chemical reactions occurring at higher temperatures. The Cl spectrum of PC/Ny6 blend (Figure 5.23) contains the ions at miz 114 and 509 corresponding to protonated molecular ions of caprolactam and cyclic dimer of PC, respectively. The peak at m/z 112 can be assigned to an unsaturated aliphatic isocyanate whereas the ion at m/z 324 corresponds to an unsaturated ester (Table 5.4). The peak at m/z 367 may possess an open-chain isocyanate-ester or a cyclic urethane-ester structure. TTie pyrolysis compounds containing... 

Aliphatic isocyanates n. Open chained structures containing the isocyanate group, -N=C=0. Aliphatic isocyanates are used extensively in paints and coatings, providing excellent UV stability, chemical... 

Rg.19 Chemical structures of thermoplastic SMPs. (a) Aliphatic polyetherurethane TFX, which is prepared from methylene bis(p-cyclohexyl isocyanate) (H12 MDI), 1,4-butanediol (BD), and poly(tetramethylene glycol) (PTMG). (b) Multiblock copolymer PDC prepared from PPDO-diol, poly(p-dioxanone-diol) TMDl, 2,2(4),4-trimethylhexanediisocyanate PCL-diol, poly(f-caprolactone-diol). Reprinted by permission from ref. [85]. Copyright 2006, Nationtil Academy of Sciences, U.S.A. 

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