The effects of isocyanate index on the properties of aliphatic waterborne polyurethaneureas

Abstract

ABSTRACT:The aliphatic waterborne polyurethaneureas (WPU) with different isocyanate index (R) were synthesized by isophorone diisocyanate (IPDI) and polyester glycol via prepolymer mixing method. The effects of the R value on the structure and the properties of the resultant polymers have been analyzed. The polymer with a certain R value (R ¼ 1.44) exhibited excellent mechanical properties with both high tensile strength (55 MPa) and high elongation at break (1400%). The water resistance and the thermal stabilities of WPUs have been improved with the increase of R. The results were interpreted in terms of the structures associated with the micro-phase separation. According to differential scanning calorimeter (DSC) analysis, the microphase separation degree was elevated by increasing R value. FTIR spectrum showed the more R value, the more hydrogen bonded urea groups. No crystallinity was found in X-ray diffraction (XRD) patterns showing the typical amorphous morphologies of IPDI-based WPUs. Thus the primary driving force for microphase separation was the hydrogen bonding between urethane and urea groups, making significant influence on the properties of WPUs, as shown in dynamic mechanical analyzes.

Relationship between reagents molar ratio and dispersion stability and film properties of waterborne polyurethanes

“…Water absorption is an important parameter of polymeric films since it could limit the use, storing or type of application [25]. The water absorption may be attributed to the localized polarity, number of ionic groups at the surface and sample crystallinity.…”

“…TgSS peaks [25] like in blocks based on HDI or MDI [5,26]. Soft domain glass transition temperature (T gSS ), melting temperature (T mSS ) and enthalpy ( H mSS ) of the synthesized WBPUs are summarized in Table 3.…”

One‐pot synthesis of palm oil‐based polyester polyol for production of biodegradable and biocompatible polyurethane

“…The nonhydrogen bonded –NH stretching is located at the wavelength range of 3400–3500 cm −1 while the hydrogen bonded –NH stretching is located at the wavelength at approximately 3336 cm −1 , suggested the –NH stretching of the polyurethanes at 3361–3365 cm −1 was hydrogen bonded. The presence of hydrogen bonding in the hard segment is known to cause phase separation in the polyurethane and resulted in the enhancement of mechanical properties of the polyurethane . This effect was observed in tensile properties and compression properties of the polyurethanes when produced at isocyanate index of 1.2 and 1.4.…”

Tetracycline release from chitosan/fish‐scale‐based membranes

“…In addition, the comparison and analysis of the results may be difficult, mainly because of poor mathematical fittings to the experimental data. A very commonly used and easy to apply semi‐empirical equation is the so‐called power law, as introduced by Peppas and coworkers . Its linearized form is shown in the following equation: where t is the drug release time, n is the release exponent, which is indicative of the mechanism of drug release, and k is the apparent release rate, which incorporates structural and geometric characteristics of the release system.…”