Relation between the phase structure and surface structure of films made from polyurethane dispersions

Abstract

Segmented polyurethane dispersions (SPUD) having carboxyl groups in soft segments (SS) or hard segments (HS) were synthesized. Phase, surface, and interface structures of films made from those SPUD were examined by differential scanning calorimeter (DSC), contact angle, and X-ray photoelectron spectroscopy (XPS) measurements. Segmented polyurethanes (SPU) with the same structures as SPUD were also synthesized in the organic solvent system, and the properties and behaviors of these SPU films were compared with the SPUD films. It was indicated by the DSC measurements that the film made from SPUD having carboxyl groups in the soft segments (S-SPUD) had higher crystallinity and crystal growth rate than the film made from SPUD having carboxyl groups in the hard segments (H-SPUD) in spite of steric hindrance. On the other hand, the film made from SPU having carboxyl groups in the hard segments (H-SPU) had higher crystallinity than the film made from SPU having carboxyl groups in the soft segments (S-SPU). Further, the crystal growth rate of SPU was faster than that of SPUD, regardless of the position of carboxyl groups. These results indicated that the phase structure of SPUD film was affected by the phase structure in the dispersion particle. Surface and interface structure of SPUD film was rearranged with a change of the phase structure. But the degree of this change was higher in the surface structure than in the interface structure.

Polyurethane dispersions derived from polycarbonatediols by a solvent‐free process

“…Then the solvent is removed to obtain the desired aqueous polyurethane dispersion. The effects of various factors such as the structure and content of diisocyanates, polyols, carboxylic diols, neutralizing agents, chain extenders on the preparation of polyurethane dispersions and their properties have been studied extensively 4–11, 17–20…”

Clear polyurethane dispersions of nanometer size derived from carboxylic polycaprolactonediols

“…The incorporation of ionic groups into polyurethanes is a practical method to obtain aqueous polyurethane dispersions,1, 2 and various polyurethane cationomers5–8 and polyurethane anionomers9–17 have been described in the literature. The properties of the polyurethane dispersions are related to their chemical structure 17–22…”

Effect of composition on aqueous polyurethane dispersions derived from polycarbonatediols

“…Incorporation of ionic groups into polyurethanes is a practical method for obtaining aqueous polyurethane dispersions,1, 2 and various polyurethane cationomers5–8 and polyurethane anionomers9–17 have been described in the literature. The properties of polyurethane dispersions are related to their chemical structure 17–22. Polycarbonatediols are recently commercialized polyols and are claimed to provide good resistance to hydrolysis, heat aging, oil, weathering, and fungi 23.…”