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Aqueous dispersions of polyurethane (PU) ionomers were prepared from hydrogenated diphenylmethane diisocyanate (H12MDI), poly(tetramethylene adipate) glycol (PTAd), bisphenol A propylene oxide ether glycol (LER), and dimethylol propionic acid (DMPA) as potential ionic centres. The urethaneforming reaction was carried out in N‐methyl‐2‐pyrrolidone (NMP) with dibutyltin dilaurate (DBT) as catalyst. The effects of DMPA and bisphenol A polyol on the particle size of the dispersions, and the physical properties of the emulsion cast films were determined. It was found that the particle size decreased with DMPA, and increased with bisphenol A polyol contents. Initial modulus and tensile strength of the emulsion cast films increased, and the elongation at break decreased with DMPA and bisphenol A polyol contents. The results were interpreted in terms of increased interchain Coulombic forces and urethane linkages with DMPA, and increased chain rigidity of PU with bisphenol A polyol incorporation.
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Lee et al. (1992) studied this question.
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