In this study, we report the effect of the DMPA/PTHF molar ratio on dispersion properties of the MDI‐based hydrophilic polyurethane dispersions. In addition, the effect of the DMPA/PTHF molar ratio on the crystallinity and thermal properties of the polyurethane films prepared from dispersions are also discussed. The variation in stability was studied using a particle size analyzer. DSC and XRD analyses were used to study variations in crystallinity of films with the change of DMPA/PTHF molar ratio. FT‐IR spectra were used to monitor the formation of hydrogen bonds through urethane linkages to produce hard‐segment crystalline areas. The zeta potential increased with the increase of DMPA/PTHF molar ratio (hard‐segment content), while particle size of polyurethane particles decreased. Hence, the stability of dispersions was increased with DMPA/PTHF molar ratio due to the increase of hydrophilicity in polymer chain. Crystallinity of the films was increased with DMPA/PTHF molar ratio due to the increase of interchain interactions through Coulombic interactions and hydrogen bonding. Consequently, crystalline melting temperature was increased with the increase of DMPA/PTHF molar ratio. However, molten films formed crystalline soft segments instead of crystalline hard segments during slow cooling.
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Senevirathna et al. (2016) studied this question.
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