Coalescing agents are used in dispersion paints for optimizing the film formation process of the polymeric binder particles.
The film formation process in dispersion paints involves the coalescence of the polymeric particles, during and after the evaporation of the diluents (notably water), thereby permitting contact and fusion of adjacent polymeric dispersion particles.
Coalescing agents typically reduce the minimal formation temperature and as a consequence to optimize film coherence and properties such as scrub resistance, mechanical properties as well as appearance.
Polymer dispersions, used as binders in dispersion paints, consist of particles finely distributed in water. The layers of surfactant and/ or colloid, present on the surface of the particles, act as stabilizers, preventing coagulation and provide stability in the dispersed stage. The particles have diameters of about 30 to 500 nm, or even higher in case of course, opaque dispersions. The film formation process, after application, involves evaporation of the solvent and formation of a continuous polymer film by purely physical means.
posted by sheldon Pettit, Technical Service/ Customer Assistance at cosultants to the wood finishing industries
explains why the difficulties i have seen in past generations of acrylic emulsion finishes have failed to meet up to the latest ones being introduced. however it does not go into what concerns me most as to the seemingly chain scission causing linear cracking of the totally cured film?
Alternative method for efficiency testing - Mar 28, 2012
posted by Titus Sobisch, R&D - Applied/ Formulation/ Product development at L.U.M. GmbH
Using multisample analytical centrifugation for polymer dispersions we often observe a marked increase in transmission of the sediment when high pressure acts on the sediment due to centrifugal force. This might be an alternative method for fast screening of efficiency of coalescing agents. Likely, the effect only occurs above the MFFT.
Even more it can measure stability and test for freeze/thaw stability.
posted by Ankush Panchagade, R&D - Applied/ Formulation/ Product development at Akzonobel coating India ltd.
small & sweet, it gives an basic idea for selection of coalescing agent in formulation. very good brief introduction but it will again more intresting when some exampls. with three part would be explained.