Manual applied polyurethane-urea: High performance coating based on CO2-based polyol and polyaspartic ester

A novel isocyanate-free strategy towards preparation of polyurea by a ring-opening reaction

“…17,18 Adoption of this special type of amine compound allows the application of PAE by hand because of the slower reaction rate. 19 The mechanical properties of PAE are close to those of sprayed PUA, but the thermal stability and chemical resistance are not superior enough. 20–22 This phenomenon is probably because the bonding energy of the hydrogen bonds in PAE prepared using these special amine groups is lower than that of sprayed PUA, which has an effect on its thermal stability.…”

Construction of Ultralow-Molecular-Weight CO2–Polyols with Self-Catalytic Performance in Polyurethane Preparation

“…Fixation of CO 2 as a renewable C1 feedstock into chemicals and materials is an ideal route to reduce carbon emissions. , Life-cycle assessment shows that compared with the production of traditional polyether polyols, poly­(ether carbonates) polyols (CO 2 -polyols) containing 20 wt % CO 2 units can reduce greenhouse gas emissions by about 11–19% and energy consumption by 13–16%. , On the other hand, polyurethane (PU) based on CO 2 -polyol shows excellent wear resistance, solvent resistance, and mechanical performance, as well as better hydrolysis and oxidation resistance. − Therefore, copolymerization of CO 2 and epoxide in the presence of initiators to yield CO 2 -polyols is considered to be a promising process. ,, In this route, initiators play important roles in tuning the molecular weight (MW), copolymerization efficiency, carbonate unit (CU) content, and product selectivity. For example, our groups found that the role of acid-based initiators significantly relies on their acidity in the double metal cyanide (DMC) complex-catalyzed oligomerization of propylene oxide (PO) and CO 2 . , The weak organic acid (p K a1 : 4.43–4.72) acts as the chain transfer agent (CTA), while the strong organic acid (1.87 < p K a1 < 4.2) functions as the initiate-transfer agent, that is, first initiating PO homopolymerization and then the formed polyols subsequently in situ act as the new CTA for the copolymerization.…”

High-Performance Polyurea Improved by Reactive Nanocluster for Antibiofouling

“…Such a quick reaction prevents polyurea from sufficient wetting on the substrate, resulting in poor adhesion. To slow it down, the reaction was usually carried out with a large amount of polar solvent at a low temperature. , On the other hand, secondary amines, such as polyaspartic ester (PAE), have been used to reduce the reaction rate through steric hindrance and electron-induced effects. − While PAE-based polyurea can achieve adjustable gel times and good adhesion, the weaker hydrogen bonds formed by secondary amines result in relatively low tensile strength (<10 MPa). , To improve the tensile strength, the content of hard segments in polyurea was increased, but this usually made polyurea to be more brittle. Alternatively, nanofillers were added to improve the strength.…”