Investigation of the effect of precoalescence or postcoalescence crosslinking on film formation, properties, and latex morphology

Abstract

Latexes have many product applications including functioning as a binder in coatings. For many years, coatings researchers in industry as well as in academe have been exploring various modes of crosslinking latexes. Quite often, the goal of preparing crosslinked latexes is to upgrade film properties relative to the film properties of uncrosslinked latexes. In the present report, the synthesis and properties of crosslinkable acrylic latexes prepared with either an internal crosslinker (1,3-butylene glycol dimethacrylate)-''precoalescence crosslinking''-or an external crosslinker (adipic dihydrazide)-''postcoalescence crosslinking''-at various levels of crosslinking were studied. For postcoalescence crosslinking, diacetone acrylamide was copolymerized into the latex to provide sites for subsequent reaction with adipic dihydrazide. Fundamental properties of films cast from the two types of latexes were systematically compared. These properties included gel content, dynamic mechanical properties, nano-indenter hardness and modulus, stress-strain properties as well as the characterization of latex morphology by atomic force microscopy (AFM). In addition, some specific end-use properties were determined. This study assesses the effect of type (precoalescence or postcoalescence) and level of crosslinking on the film formation process and the resulting fundamental and end-use properties as well as resulting latex film morphology.

RETRACTED: Synthesis and characterization of two novel heterocyclic monomers bearing allylic function and their applications in the epoxy-acrylic-amine waterborne coatings

“…An optional method is to improve the cross-linking property [1,[27][28][29][30][31]. Chemical reactions between different polar groups not only facilitate cross-links and thus enhance the physical and chemical integrity of the coalesced film, but also reduce the number of polar groups and thereby lower the water sensitivity of the coatings [15,27,31].…”

“…blocked isocyanates and acetoacetate groups, etc. [7,15,[27][28][29][30][31]. Cross-linking property of a coating is known to be impacted by the number density of these reactive polar groups.…”

In-Situ AFM and EIS Study of Waterborne Acrylic Latex Coatings for Corrosion Protection of Carbon Steel

“…14, 16 The water resistance of the SALH coating could be attributed to the densely packed nanoparticles in the coating, and particularly to a high level of hydrophobicity. 22,40,41 In contrast, the SALL coating has a low Tg, which can decrease the strength of the film by influencing the latex film formation process.…”

“…42 In the case of the SALL coating, probably most of the curing reactions take place within the styreneacrylic emulsion particles, without considerable crosslinking across the boundaries. 16 The particle boundaries are weak spots within the coating, where corrosion attacking may be initiated by aggressive ions in corrosive solution. 42 Moreover, the boundaries and voids between the particles in the SALL coating are larger than that of SALC and SALH coatings.…”

“…15 Recently, considerable efforts have been made to improve anticorrosion performance of waterborne coatings by enhancing the crosslinking property, to gain increased chemical resistance and mechanical properties of the coatings. 14,[16][17][18] The latex film formation involves water evaporation with the consequent packing of the particles, then the particles deform to fill the void spaces, and finally the polymer chains that are in different particles undergo interdiffusion to delete the particle boundaries. 14,18 The Tg plays an important role in determining the extent of particle deformation.…”