PU Solution Preparation and Solvent Systems
topic
Polyurethane coating solution preparation dissolves PU polymer at 15 to 35 percent solid concentration in DMF or DMF-MEK solvent mixtures, with solution viscosity of 20000 to 100000 centipoise at coating temperature adjusted by polymer concentration and molecular weight selection, and pigment dispersion addition for coloured coating layers, requiring enclosed mixing and solvent handling systems meeting industrial hygiene standards for DMF as a reproductive toxin subject to occupational exposure limits.
Role
Provides the PU solution of defined viscosity and solid content required for wet coagulation coating, with solution viscosity being the primary parameter controlling coating weight by knife application and the cell structure of the coagulated microporous layer that determines the breathability of the finished coating, requiring systematic solution quality control through viscosity measurement and solid content verification before each production run.