Because of the presence of VOC content in paints and coatings, formulators have faced a serious challenge – how to develop a high-solids polyurethane system that has low viscosity for easy usage as well as optimum performance while complying with regulations.
One answer to this question in the use of low-molecular weight polyols to create a lower-viscosity formulation that needs less solvent. Unluckily, reductions in polyol molecular weight often lead to systems that support cure too quickly and don’t perform well in the field. In case of the absence of molecular weight reductions, polyols essentially have the tendency of high intrinsic viscosities, which make it very difficult to remove solvent from the formulation.
Reactive diluent are low-viscosity coreactants that are developed specifically to reduce VOCs through a reaction with the polymer matrix. As solvents, they lessen polymer viscosity without increasing VOCs.
Reactive diluents normally take the form of blocked or concealed sources of active hydrogen. Aldimines and ketimine are instances of blocked amino compounds. Oxazolidines are a good example of blocked amino alcohols. Aldimines and hampered amines are generally quite low in viscosity (less than 5,000 cps at 100 percent solids). They are quick reactive with isocyanate and often suffer from uninvitingly lessen pot life. Even then, they still remain quite attractive for applications where highly rapid cure is required.
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