The Resin blend consists of various amine terminated molecules of varying sizes and types.
The choice of which amines to include and the ratio among the amines, will determine the performance and the processing of the polyurea. To be a “pure polyurea” there can be NO (zero) “intentional hydroxyls” added to the system. If there are hydroxyl containing products (polyols) it will be a ‘hybrid’ coating.
Hybrid systems have their place. They are good systems for certain applications. There has been significant confusion in the marketplace between a true “Pure” polyurea and a hybrid. A coating system with hydroxyls (hybrid) will require a catalyst to complete the reaction. This catalyst will cause the polymer to have the difficulties sited above.
The choices of amines include: long chain “backbone” polyetheramines like BASF’s PEA D-2000 and PEA T-5000. These are the basis of the system. While PEA T-5000 is tri-functional, it does not act like a traditional cross-linker. This is due to the high chain length between the cross-links, or better in this case – branching. It is important to add some of the PEA T-5000 however because this “branching” will give the polymer a tighter network. All polymers oxidize or degrade over time. Some, more than others. Polyureas do not have a particular problem with this, but the addition of T-5000 will give the polymer a much longer life. This is especially true in submersion applications.
The short chain curatives may be aliphatic or aromatic. Aliphatic diamines like BASF PEA D-400 are very fast reacting. If cross-linking is desired, BASF’s PEA T-403 is short compact and tri-functional to provide efficient cross-linking. Higher cross-linking will give higher temperature resistance, higher tensile, improved solvent and chemical resistance, but will lower the elongation, tear strength, impact strength. Aromatic diamines like DETDA build in the polymers strength and rigidity.
Secondary diamines like PolyLink 4200 slow down the reaction times and help them process easier. PolyLink 4200 improves the polymer properties with better flexibility, lower water absorption, higher impact strength, better abrasion resistance, better chip resistance, less “orange peel” effect, better flow out, better self-leveling, and less shrinkage. PolyLink 4200 also gives you better substrate wetting and flow, better substrate adhesion, better inter-coat adhesion, and longer “open times” between multiple passes. You will get smaller droplets, less “fingering” and “roping” lower mix viscosity, Less build-up on the gun tip, less nozzle plugging, improved mechanical mixing, greater control on the thickness per pass, and higher productivity with lower down time. The ratio of the PolyLink 4200 to the DETDA will determine the speed of reactivity, the rigidity and hardness of the coating.
Various additives may also be included in the B-Side Resin blend. Adhesion promoters such as PolyGrab ES-187 and PolyGrab AS-1100 will help improve substrate adhesion and should always be used on concrete applications. In applications where UV resistance is important, all aliphatic systems should be used. UV stabilizers, such as PolyStab 100 should also be added to these aliphatic coating systems. In pure polyurea systems, pigments dispersed in BASF PEA D-2000 like those from Rebus Inc. should be used.
In caulk systems, the reaction times need to be much longer than in coating applications. Many of the same chemicals are used but in different ratios. For example, significantly higher levels of PolyLink 4200 will help delay the gel times and give better mixing and flow out at the lower mix pressures usually used for the caulk application.
In all polyurea applications, the coating formulation is only 1/3 of the critical success. Proper substrate preparation is necessary and proper equipment and mixing at proper temperatures and pressures is critical.