Waterborne polyurethane is a new type of polyurethane system in which water replaces organic solvent as dispersing medium, also known as water-dispersing polyurethane, waterborne polyurethane or water-based polyurethane.Waterborne polyurethane uses water as the solvent, which has the advantages of no pollution, safety and reliability, good mechanical properties, good compatibility and easy modification.
Synthesis of waterborne polyurethane:Polyurethane synthetic reaction process is neither polycondensation, nor addition polymerization, but somewhere in between, known as first step addition polymerization process using the reaction of NCO and OH reactive made at the beginning of polymers, and then in the early adding hydrophilic chain extender DMPA polymers and small molecular chain extender DEG and chain extension reaction, increase of polymer molecular weight, add the neutralizer TEA for neutralization reaction, fast mixing, obtain the polymers' final phase transfer method is adopted to improve the emulsification is a certain amount of deionized water slowly add pre polymers, high-speed mixing shearing emulsification at the same time, the aqueous polyurethane dispersions,Decompression distillation is then performed to extract the solvent.
Simple classification of waterborne polyurethane:

According to particle size and appearance, it can be divided into aqueous polyurethane dispersions (particle size <0.001 micron, transparent appearance), waterborne polyurethane dispersion (particle size: 0.1-0.1 micron, translucent appearance) and waterborne polyurethane emulsion (particle size: >0.1 micron, opaque appearance).
According to the charge property of hydrophilic group, the waterborne polyurethane can be divided into anion type waterborne polyurethane, cationic type waterborne polyurethane and non-ionic type waterborne polyurethane.Among them, the anion type is the most important, which can be divided into two categories: carboxylic acid type and sulfonic acid type.
According to the synthetic monomers of different waterborne polyurethane can be divided into polyether type, polyester type and polyether type, polyester mixed type.According to the choice of different diisocyanates, water-based polyurethane can be divided into aromatic and aliphatic groups, or specifically into TDI type, HDI type and so on.
Water - based polyurethane can be divided into one - component water - based polyurethane and two - component water - based polyurethane.
Introduction to waterborne polyurethane application:
1. Leather: including leather finishing agent, artificial leather resin and resin for shoe materials
2. Adhesives: water-based polyurethane adhesive is mainly through the physical force between the adhesive layer and the adhesive to obtain a good bonding effect.It can be used as the adhesive of fabric, non-woven cloth, etc. It is more suitable for the material of porous surface and material that is easy to be swollen by solvent to bond, and it is pollution-free, low cost, good bonding effect and has a broad application prospect.Because most waterborne polyurethane adhesives do not contain NCO group, they are mainly cured by the cohesive force and adhesive force generated by the polar groups in the molecule
3. Fabric finishing: including waterproof and moisture permeable coating agent, wool fabric anti-shrinkage finishing agent, anti-static finishing agent and non-ironing finishing agent
4. Coating: water-based polyurethane can be used for furniture, wood, automobile, building, paper, glass fiber, plastic, industrial and anti-corrosive coatings, and can also be used for special coating in aerospace, ships, optical fiber, military industry and other departments and fields.

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