Synthesis of polymeric dyes based on self-colored network of castor oil-based waterborne polyurethane

The development of vegetable oil-based polymers was particularly suitable for the era of increasingly scarce petroleum. Self-colored castor oil-based waterborne polyurethanes (PUs) were successfully synthesized based on castor oil and 1-amino-4-hydroxy-2-(6-hydroxyhexyl) anthraquinone (DR) as polyols. The UV-Vis spectrum showed that the addition of carboxylic acid groups make the spectrum of the PU produce the hyperchromic effect under alkaline conditions. Castor oil-based waterborne colored PUs possessed excellent stability under weak alkaline conditions. The connection of castor oil caused the PU to constitute soft polymer networks. PU coatings on cotton fabrics possessed excellent color properties. The urethane groups in the PUs formed hydrogen bonds with the hydroxyl groups on the cotton fibers and the polymer network structure formed by the PU coating itself made the color fastness of the cotton coatings reached grade 5. With the increase of castor oil content, the degradation rate of castor oil-based waterborne colored PU increased from 3.45% to 3.65%. This work provides a way to impart excellent color properties and fastness to PU coatings by inserting dye molecules and vegetable oils into the PU macromolecular chain.