The Synthesis And Properties Of Underwater Fast-Curing Polyurethane And Waterborne Polyurethane Based On Chain Extenders With Multiple Sulfonic Groups

Polyurethanes(PUs)is a general term for polymers with repeated-NHCOO-groups on the main chain based on the reaction of polyol and polyisocyanate.which have been widely used in light industry,such as electronics,textiles,medical,aerospace and other fields due to their excellent physical and chemical properties since its discovery in 1937.By adjusting the structure of polyols and isocyanates,a variety of functional PU materials can be synthesized,However,some of the traditional PUs require organic solvents in engineering applications,which are harmful to the environment and human health.In order to replace these traditional VOCs-based PUs solvent-free and water-based PU materials,which are environmentally safe and have low VOCs emission,are the research hotspots of the current PU industry.Based on the current environmental protection requirements and the development trend of the PU industry,two types of environmentally friendly functional Pus have been developed in this paper:The first category is solvent-free bioinspired PU adhesives for underwater bonding.Although good progress has been made in solvent-free PU adhesives,these PU adhesives(such as thermoplastic PU adhesives,hot-melt PU adhesives,etc.)generally need to be melted or plasticized during applicatuon.Moreover,these adhesives are mostly used to bond the substrates in dry or humid environments and there are few reports on PU adhesives that can be quickly bonded under water.Aiming at these problems,a novel mussel-inspired solvent-free PU adhesive with catechol and NCO groups is synthesized in this paper.Owing to the rapid reaction of isocyanate groups with water,this biomimetic PU adhesive can achieve the goal of the underwater bonding,and the highest bonding strength can reach 1.2MPa after 2 min.underwater curing.The second category is waterborne polyurethane(WPU)based on chain-extender carrying multiple sulfonate groups.Most of current hydrophilic chain extenders used in WPU are those carrying one hydrophilic groups,(such as 2,2-dimethylolpropionic acid,DMPA and sodium ethylenediaminoethanesulfonate,AAS),We are interested in the influence of the chain extender carrying multiple sulfonate groups on the properties of the resulting WPU.Thus,two kinds of sulfonic acid chain extenders with 2 and 4 sulfonic ions are synthesized,and the effect of the number of ions in the chain extender on the emulsifying properties,mechanical properties and thermal properties of WPU were investigated.The results show that the increase of the number of ions on the chain extender is helpful for the waterborne polyurethane to achieve good emulsification performance at a lower dosage of chain extender.The tensile strength of the prepared WPU film can reach up to 35 MPa,and the adhesion force on the surface of the stainless steel substrate is grade 0(international standard).