and as a hardener for epoxy resins. When monoethylene glycol as a diol is replaced with isosorbide in the polyester polyethylene terephthalate (PET), polyisosorbide terephthalate (PIT) is obtained, which is characterized by an extreme thermal stability (up to 360 °C under nitrogen). However, the inherently lower reactivity of the secondary hydroxyl groups in isosorbide cause in comparison lower molecular weights and high residual contents of terephthalic acid, which leads to the insufficient chemical stability of the resulting polymers. Therefore, today's polyesters with isosorbide and monoethylene glycol are examined as diol components that show improved properties such as less discoloration. Isosorbide is of also of interest as a precursor to polycarbonates,. It could in principle replace the bisphenol A, which was identified as xenoestrogen. Limitations of isosorbide-based polycarbonates are their unsatisfactory temperature resistance and limited impact resistance, which can be improved though by the addition of comonomers to the isosorbide or by polymer blends. Isosorbide, a diol, is a precursor to In polyurethanes. or as a building block for the polyol [29] It could be converted to the diisocyanate component as well as a chain extender. By reacting isosorbide with epichlorohydrin, isosorbide bis-glycidyl ether (a bis-epoxide) is formed, which could be used as a replacement for the analog bisphenol A bis-epoxide. Isosorbide bis-glycidyl ether can be crosslinked to a thermosetting epoxy resins with suitable curing agents, such as polyamines or cyclic acid anhydrides. These resins are used as adhesives, paints or coatings for food cans. Furthermore, polyoxazolidones are described which can be obtained by reaction of isosorbide diglycidyl ethers with diisocyanates. Polyoxazolidones could find use as rigid, highly branched and solvent-resistant thermoset plastics in the electrical and electronics industry. See also Dianhydrohexitols, isomers of isosorbide References Antianginals Diols Furofurans X