Search

In this study, core‐shell structured cationic waterborne polyurethane (WPU) dispersions with high solid content were prepared. To this end, prepolymer A was synthesized from polytetramethylene ether glycol (PTMG), isophorone diisocyanate (IPDI), castor oil (CO) and 1,4‐butanediol (BDO) without integration of the hydrophilic groups. Prepolymer B with hydrophilic groups was prepared from PTMG, IPDI, CO, BDO and N‐methyldiethanol amine (MDEA). WPU dispersion with a core‐shell structure could be generated by mixing, neutralizing, and emulsifying of the prepolymer A and the prepolymer B. The results indicated that the generation of WPU dispersions through this technique exhibited a milky appearance while the pH values range from 5.30 to 5.60. The optimal combination of prepolymer A and prepolymer B (at a ratio of 5:5) resulted in a dispersion with the highest solid content (50.4%), lowest viscosity (69 mPa·s), and narrowest particle size distribution. As the proportion of prepolymer A to prepolymer B decreases, the tensile strength of WPU film reduces while the elongation at break and glass transition temperature increases. Moreover, initially the contact angle with water was decreased instead of increase. However, modifications in a ratio of prepolymer A and B was not showed any significant impact on the thermal stability performance of the WPU films. [ABSTRACT FROM AUTHOR]

High solid content CO2-based cationic waterborne polyurethanes (CWPUs) were prepared using CO2-polyols as soft segment and N-methyl diethanolamine (MDEA) as hydrophilic group. The resulting stable aqueous dispersion displayed a high solid content of 52% with a low MDEA loading of 3.52 wt%. This novel structural CWPU can provide excellent adhesive strength, whose T-peel strength could reach 173.48 N/5cm, 20% higher than that of ester-based cationic waterborne polyurethane (87.55 N/5cm). The CO2-based CWPU film showed only 2 wt% swelling percentage after 240 min immersion in water, and no change was observed during its immersion in 5 wt% sodium hydroxide solution. The tensile strength of CO2-WPUs dropped slowly to 91.2% after 480 min immersion in a 5 wt% sodium hydroxide solution, whereas that of ester-based CWPUs dropped quickly to 32% after 240 min and their mechanical properties were lost after 360 min immersion. Meanwhile, the retention of the tensile strength of the CO2-CWPUs was 81.5% even after 720 min immersion in 10 wt% H2O2 solution, while it was only ca. 38% for the ester-based CWPUs. These results indicated that the cationic CO2-based CWPU may be promising waterborne adhesive with outstanding ageing resistance due to its synergistic effect from carbonate and ether groups of CO2-polyol structure. [ABSTRACT FROM AUTHOR]