Diary (June 17, 2015)

Online diary of Karl Jones for Wednesday June 17, 2015.

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Diary

Amine blush

epotek.com

Ambient cured epoxy sometimes appears sticky, tacky, and less glassy and smooth on the surface, when compared to oven cured samples. The cause is most likely due to a side chemical reaction of moisture (humidity) in the air, interacting with a curing agent. This phenomenon is known to epoxy chemists as “amine blush” or “amine bloom”.

What is Amine Blush?

Amine blush can be described as a sticky, oily, or waxy appearance on the surface layer of a cured epoxy. It can appear as greasy white spotting, or even salt-like, crystalline deposits. Many times, it can also be cloudy, milky or gray colored, with opacity and dullness. What are the differences between blush and bloom?

Amine blush and bloom generally yield the same unwanted cured appearance, but differ in their chemical mechanism. Where blush refers to moisture condensing on the surface of the epoxy, bloom or leaching is essentially the converse reaction where water-soluble compounds migrate, or “leach” to the surface, resulting in sticky deposits or patches, like water marks in the sand.

Why does Amine Blush occur?

Amine cure agents being hygroscopic (absorbing moisture), can react with moisture in the air to form ammonium carbamate by-products.

• Amine Blush (PDF)

kta.com

Epoxy coatings are some of the most widely used materials in industrial and marine environments. Epoxy materials typically have excellent adhesion, chemical resistance and water resistance, which make them first-rate candidate coatings/linings for these environments. Epoxies are formulated as two component materials, with one component housing an epoxy resin and the other component containing a curing agent. Curing agents are used to react with the epoxy resin to create a cross-linked coating resin. In fact, many epoxy materials have what is known as an “induction time,” or “sweat-in time,” where the coating is mixed and allowed to react for a period of time (e.g., 30 minutes) so that cross-linking of the components can initiate prior to application of the product. Though epoxy materials can have many co-reactive curing agents, the focus of this article is on amine cured epoxies.

Amine cured epoxies have an active amine functional group that react with the epoxy functional groups in the resin component. Amine exudate (blush) is a chemical reaction that occurs between water, carbon dioxide, and the amine component of epoxy coatings. Amines are hygroscopic, which means that they tend to absorb moisture from the air and are prone to react with available moisture and carbon dioxide.

• The Formation of Amine Exudate (Blushing) of Epoxy Coatings

Amine blush (nonfiction)

Biomakeup

Amine Blush (biomakeup) - line of biomakeup products from Human Beauty Machine - see also Beauty Duty, Beauty Patrol, Beauty on the High Seas, Mutiny of the Beauty, etc.

See Diary (January 22, 2021).

Fiction cross-reference

• Gnomon algorithm
• Gnomon Chronicles