CAUSES OF TURBIDITY AND POOR RESIN CLARITY
Silicone defoamers are formulation additives that cause mixed air bubbles to be unstable and causes self degassing. It is commonly used in all types of industrial fluids to prevent foaming during processing.
It is an integral additive in paints protective and conformal coatings as an anti-foam additive.
However, silicone defoamers and surfactants creates turbidity in a clear epoxy resins. It is purposely designed to be immiscible (will not blend with or form a stable solution) with epoxy resin polymers so when air bubbles formed from mixing of the curing agent to initiate polymer cross-linking, it causes air bubbles to be unstable. When an air bubble encounters the silicone defoamer compound within the mixture, the lamella or the skin boundary of the bubble loose structural equilibrium and causes it to burst due to the differential surface tension of the polymer resin and the suspended silicone molecules. This physical dynamics cause a defoaming action within the resin matrix.
This incompatibility between the epoxy polymer and the silicone defoamer cause turbidity and loss of optical transparency that is increasingly evident in thick castings or coatings.
MAX CLR-TC is our top coat resin system designed for thin film applications that is formulated with silicone based defoamers and surfactants to reduce the occurrence of air bubbles and surface blemishes from becoming stable as the epoxy polymer converts from a liquid to a solid plastic.
Note the turbidity of the MAX CLR-TC A/B VERSUS MAX 1618 A/B 3 INCH THICK CASTING.
4 FLUID OUNCES CAST VOLUME
MAX 1618 A/B is formulated without the use of any silicone based surfactants that causes turbidity even in very thick castings.
MAX 1618 A/B COLOR STABILITY COMPARISON
Clear epoxy systems formulated using plasticizers and accelerators such as the specimen. The left specimen demonstrates poor color stability even if it is unexposed to direct sunlight or elevated temperature. Note the MAX 1618 A/B specimen that was formed at the same time and kept in a temperature controlled (25.0°C +/- 0.5 °C) chamber that filters out any UV radiation from ambient light source.
MAX 1618 A/B DIRECT SUNLIGHT EXPOSURE STUDY
Note the low yellowing performance of MAX 1618 A/B compared to a common brand epoxy resin after equal direct sunlight exposure of 2 months.
Competitive brand clear resin system formulated with nonylphenol plasticizers after sunlight exposure
Note the absolute clarity of the MAX 1618 A/B specimen exhibiting excellent crystal clear transparency