Paint Foundations . . Bubbles, blisters, de-bubbles, break-ups and de-bubbles

Bubbles are stable dispersions formed by gases in liquid media. Pure liquid will not form a stable bubble, stirring pure liquid formed bubble density is less than the liquid, bubbles will gradually move to the surface, after reaching the surface bubble rupture, gas escape, bubble disappear. Stable bubbles are formed only when surfactant substances are mixed in the liquid

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Taking the water system as an example, the molecules of surfactants are arranged in the gas-liquid interface, the hydrophobic end is in the water phase, the hydrophobic end is facing the gas phase, the spherical bubble reaches the liquid surface, and the two gas-liquid interfaces inside and outside the bulging bubble form a mezzanine-shaped double-film layer. The liquid in the double-film layer gradually flows out under pressure and the double-film layer becomes thinner. When the thickness of the bubble wall is thin enough, the bubble is stabilized by the combination of the repel of the charge of the surfactant substance in the inner and outer layers and the elasticity of the bubble film (related to the surface tone of the membrane).
unit bubble film contains a certain amount of surfactant molecules, when the membrane is stretched deformation when the surface area of the membrane increases, the surface active agent molecules on the unit area film decrease, surface pressure increases, the membrane has greater contraction, prompting the membrane to retract. Bubbles stabilize when the contraction force is balanced with the electrostatic repulsion of the surfactant molecule.
can be seen that liquid foam can only be produced if there is a surfactant, and remains stable under the action of electrostectractive refractive force and bubble film elasticity.
coating is made up of many components, many ingredients in the formula will inevitably bring some surfactant substances, so that the coating has the effect of stabilizing foam. Compared with solvent-based paint water-based paint in the parts are more complex, will inevitably produce a stable foam, but also more difficult to deblister than solvent-based paint, so defrosting agent is one of the water-based paint must be used.
the blistering and de-foaming process actually consists of three aspects:
the process of forming and stabilizing bubbles can be seen: the whole contents of de-foaming are formed.
focus on a certain functional role, some additives are called anti-foaming agents, de-foaming agents and foaming agents.
anti-foaming agent is very easy to adsorption on the bubble membrane wall, they crowd out the surface active substances of stable bubbles, so that the surface of the bubble film pressure is reduced, the foam wall becomes thin, uneven bubble surface free energy can cause the instability of bubbles, in the process of bubble floating will be destroyed. Good anti-foaming agents inhibit excessive air bubbles during agitation and pumping.
is also known as air release agent, in general, deboist agent is dispersed in the liquid medium of non-polar substances, de-foaming agent's unique incompatibness prompts it to gather in the bubble of the air liquid interface. Bubbles are surrounded by non-polar defrost layer, and the role between the defrosting agent molecules and liquid medium is weak, one or two such bubbles close to each other will merge into a large bubble, bubbles in the liquid rise rate and the radius of the bubble squared in direct ratio, the fusion of the atmospheric bubble rise speed greatly accelerated, and reached the liquid surface, bubble burst after the foam elimination, it can be seen that the defrosting agent greatly accelerated the escape of the bubble. In addition to promoting bubble fusion, the role of de-foaming agent can also improve the speed of the rise of bubbles, even for the small bubbles not fused there is a clear effect of promoting the rise.
foam breaker can significantly reduce the surface tensor of the bubble membrane wall, so that the foam wall present on the liquid surface thin, resulting in the rupture of the membrane, to achieve the goal of deblistering.
anti-foaming agents, de-foaming agents and blisters are collectively referred to as de-foaming agents. It is often difficult for an additive to distinguish and define its anti-foaming, de-foaming and blistering effects, and de-bubble agent is a generally applicable concept.
source: Architectural Coatings Branch