Synthesis and Properties of Solvent-Free Sulfonic Acid/Carboxylic Acid-Based Waterborne Polyurethanes
A series of sulfonic acid/carboxylic acid-based waterborne polyurethanes(WPUs)were synthesized by a one-step method.By adjusting the nNCO/nOH(R value),the complex ratios of sulfonic acid/carboxylic acid-based hydrophilic chain extenders to reduce the prepolymer viscosity,the preparations of solvent-free WPUs were achieved.In this study,a series of WPUs were synthesized using polyether and isophorone diisocyanate(IPDI)as the main raw materials,bis(hydroxymethyl)propionic acid(DMPA)and N,N-bis(2-hydroxyethyl)-2-aminoethanesulphonic acid sodium salt(BES-Na)as the hydrophilic chain extenders.The influences of the R value,the neutrality degree,and the contents of the hydrophilic chain extenders(mass of hydrophilic chain extender in the percentage of total mass of prepolymer)and the ratios(amount of substance of sulfonic acid chain extender in the percentage of total amount of substance of chain extenders)were also investigated.The results show that the use of sulfonic acid/carboxylic acid compounding endows WPU with good performances.The 5%weight loss temperatures of WPU are all higher than 300℃,the solid contents are all higher than 38%,and the particle sizes show a good trend of multi-peak distribution.When the R value is1.5,the neutrality degree is100%,the total amount of chain extenders is3.55%,the proportion of BES-Na is 6%,the average particle size of WPU emulsion is 310.6 nm,the emulsion particle size has a good bimodal distribution,the ratio of large and small particle sizes is 7.8,the tensile strength of WPU adhesive film is3.9 MPa,the elongation at break is631.1%,the hardness of WPU adhesive film is up to5 H,and the adhesion grade is 0 grade,showing the best comprehensive performances.
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