Problems to be considered in the formulation of aqueous acrylic emulsions (2) : phase structure of emulsion particles and film forming AIDS

Problems to be considered in the formulation of aqueous acrylic emulsions (2) : phase structure of emulsion particles and film forming AIDS

2019-08-22

The internal structure of waterborne acrylic emulsion particles will affect several aspects of waterborne paint formulations.According to the order in which the effects are affected, the phase structure will first affect the selection and addition of the filming aid.Different phases have different hydrophilic/lipophilic characteristics, and the oleophilic properties of various coalescents are different. For example, dipropylene glycol methyl ether (DPM) is more hydrophilic than dipropylene glycol butyl ether (DPnB). Low oiliness.If the outer layer of the aqueous acrylic emulsion particles is a very lipophilic phase, the addition of DPM is not only ineffective for film formation, but also causes excess DPM to be free in water to affect other properties of the water based paint film.

Another effect of the phase structure on the aqueous paint formulation is the effect on the film quality of the waterborne paint film.The key to film quality is that during the fusion of the aqueous acrylic emulsion particles, the phases that need to be mixed are thoroughly mixed, while the phases that need to be separated remain separated.If different phases are required to participate in the fusion, a mixed filming aid should be chosen for best results.

Many domestic and foreign literatures on aqueous acrylic emulsion polymerization mostly mention the structural problems of various emulsion particles such as core shell. For example, various structures such as nuclear shell, half moon, multinuclear, hollow, and strawberry have been reported.While the description of these structures is useful for understanding the complexity of aqueous acrylic emulsion particle structures, the structure of aqueous acrylic emulsions is actually much more complicated.For example, only emulsions of single phase structured particles are absent. Particles in practical aqueous acrylic emulsions are distributed in a variety of structures, possibly with more core shells, possibly more strawberries, and the like.Waterborne acrylic emulsion manufacturers control the phase structure of aqueous acrylic emulsions by the choice of monomers, the order of addition, the amount of surfactant used, and the like.

Since the phase structure of a typical aqueous acrylic emulsion is a technical secret of the emulsion manufacturer, this information is generally not disclosed.However, suppliers will provide recommended additives and ratios for their supplied acrylic emulsions. This is often the case for different aqueous acrylic emulsions that require different combinations of additives.

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