Structural Adhesives - Part 2, POLYESTER

Let’s begin with Polyester. Polyester is a polymer which contains the ester functional group in their main chain. Depending on the chemical structure polyester can be saturated (thermoplastic) and unsaturated (thermoset).

Translation #1 – saturated/thermoplastic turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently. Saturated polyesters are primarily used in the paint industry for general industrial coating.

Translation #2 - unstaturated/thermoset is material that irreversibly cures. The cure may be done through heat or a chemical reaction. Unsaturated polyesters are used for castings, glass fiber laminates and adhesive systems. It's these adhesive systems that are used in the stone industry – primarily in the stone countertop segment. Unsaturated polyesters are two part systems consisting of a resin and peroxide based catalyst, a strict mix ratio is not required for cure. Unsaturated polyesters have greater shrinkage and less chemical resistance than epoxy adhesives.

Benefits of Unsaturated Polyesters:

• Fast curing
• Low cost
• Perfect for more porous stone, such as Marble

Specific uses with stone can be:

• Interior use
• Laminating Countertop Edges
• Rodding Thin Stone and Countertops
• Countertop Seaming

Have you used Polyesters? If so, what has been your experience with them. If not, why not? * * Stay tuned for the next part of our Structural Adhesives postings as we tackle Epoxy next. * *

Structural Adhesives - Part 1

According to McGraw-Hill Science & Technology Dictionary structural adhesives are capable of bearing loads of considerable magnitude. A structural adhesive will not fail when a bonded joint prepared from the thickness of metal, stone or other material typical for that industry is stressed to its yield point.Structural adhesives are adhesives that are used in high strength-permanent applications. Most often these adhesives are the primary means of attachment in structural applications.

There are many different types of structural adhesives, but, the three main types are Epoxies, Polyesters and Polyurethanes.

In our next few posts, we try to explain the chemical make up, uses, and benefits of these three types of structural adhesives.