Advances in Waterborne Polyurethane and Polyurethane-Urea Dispersions and Their Eco-friendly Derivatives: A Review

Abstract

Polyurethanes and polyurethane-ureas, particularly their water-based dispersions, have gained relevance as an extremely versatile area based on environmentally friendly approaches. The evolution of their synthesis methods, and the nature of the reactants (or compounds involved in the process) towards increasingly sustainable pathways, has positioned these dispersions as a relevant and essential product for diverse application frameworks. Therefore, in this work, it is intended to show the progress in the field of polyurethane and polyurethane-urea dispersions over decades, since their initial synthesis approaches. Thus, the review covers from the basic concepts of polyurethane chemistry to the evolution of the dispersion’s preparation strategies. Moreover, an analysis of the recent trends of using renewable reactants and enhanced green strategies, including the current legislation, directed to limit the toxicity and potentiate the sustainability of dispersions, is described. The review also highlights the strengths of the dispersions added with diverse renewable additives, namely, cellulose, starch or chitosan, providing some noteworthy results. Similarly, dispersion’s potential to be processed by diverse methods is shown, evidencing, with different examples, their suitability in a variety of scenarios, outstanding their versatility even for high requirement applications.

Design of a Waterborne Polyurethane–Urea Ink for Direct Ink Writing 3D Printing

“…Additionally, the nature of this kind of water-based systems allowed the incorporation of hydrophilic nanoentities such as cellulose derivatives [17] and/or plant extracts [18,19], which can also be used as natural surfactants for other nanoentities like graphene [20]. This incorporation of nanoentities can lead to the realization of a final printed piece with different properties or even new functionalities.…”

Preparations of Poly(lactic acid) Dispersions in Water for Coating Applications

“…Water, indeed, is considered as a cheap, safe, non-toxic and environmentally benign solvent [ 14 ]; however, polymers are rarely soluble in water. A typical method to use water as a vehicle, in spite of the absence of solubility, is the preparation of polymer latexes consisting of polyacrylate, polymethacrylate and more recently, polyurethane as well [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Water dispersions are gaining land in many application fields such as paints [ 23 ], adhesives [ 24 ] and inks [ 25 , 26 ], particularly for the food packaging sector [ 27 , 28 ], where the restrictions on the possible substances used forced the producers to substitute old technologies with safer ones.…”

Efficient and Fast Removal of Oils from Water Surfaces via Highly Oleophilic Polyurethane Composites

“…This methodology allows to exploit both the potential of synthetic materials and the cost-effectiveness of natural ones with the aim of improving chemical-physical characteristics [ 30 , 31 , 32 , 33 ]. Polyurethane (PU) foams represent one example of synthetic materials that are widely used for the removal of oils from water, because these polymers possess a large specific area, low density and can be ultralight [ 34 , 35 ]. They are commonly synthesized by the reaction between a polyol and a polyisocyanate, catalyzed in different manners [ 36 , 37 , 38 , 39 ].…”