Custom Potting Compounds

John Maher: Hi, I’m John Maher, and today I’m here with Bob Baker, president of Key Polymer, a manufacturer of specialty adhesives and chemical compounds, and today we’re talking about custom potting compounds. Welcome, Bob.

Bob Baker: Thank you very much, John.

John: Bob, tell me what is a potting compound?

Bob: John, whenever electrical components are in some type of a housing or enclosure, whether it’s a group of wires that have come together at the back of a connector or the back of a switch, a sending unit, or maybe even a part that’s set onto a circuit board.

There’s an opportunity for those parts and servers to be damaged. They could be damaged by moisture. They could be damaged by vibration under the hood. They can have antifreeze or coolant or transmission fluid spilled on them.

In order to protect those parts, a pour of a very durable chemical product, based on either epoxy resin or polyurethanes, is specified. When this pour is done, the product is now protected from vibration.

Is protected from spills. Also, its long term durability is enhanced, because, in the process of handling the wires, the circuit, the connectors are now sealed, invisible and untouchable.

John: Are there off the shelf potting compounds that a manufacturer could buy, and when would those be used?

Bob: Sure, John. There are thousands of off the shelf potting compounds, and they have the widest range of properties. They have the widest range of compatibilities. However, the last one or two percent that makes them ideal for an application is sometimes missing.

For example, you may have a potting compound off the shelf that meets all the requirements, but it’s a little bit slower than the engineer designing the equipment would like to have for their setup time, and changing the setup time very often changes some of the other properties.

Therefore, the customization opportunity is to take with standard and make small adjustments that make very significant improvements for the end user. Sometimes those improvements are not the downstream performance but, as I said, they’re the process ability.

In other cases, just a simple situation, the customer wants color matching, that their components carry the corporate colors or that the potting and encapsulating material is close in color to the enclosure or housing, or sometimes to differentiate one range of their product line from another.

In some cases, the customization actually is related to end product performance. For example, a standard product generally meets the requirements, but it fails in contact with the most up to date engine coolants.

The prospective customer, the specifying engineer, could attempt to screen hundreds and hundreds of off the shelf potting compounds to go with their components, or they could utilize the resources of a firm like Key Polymer, where the complete range of requirements is considered and a custom product is submitted that meets the wide range of requirements.

John: How do you work with them in terms of creating these custom potting compounds? They basically just give you a list of what their specifications are and then you work with them to make the potting compound according to those specifications?

Bob: John, that’s a start, but in addition to the specifications, Key Polymer also works with the physical parts. One of the features that we offer to our customers is that we do prototyping in our facility.

So that when we do make a submission of the customized material to them, if not fully evaluated, it’s been screened and will save them time when they go to do their own evaluation.

For example, there are different types of plastics that make up the housings that are going to be potted. We’ll test for initial adhesion. There are complex products that require a viscosity capable of flowing under and around the parts.
We’ll validate the viscosity and adjust it if necessary. Then our housings that have small openings in them, so the viscosity has to be high enough not to flow out. We’ll do that evaluation.

John: Does the company give you a sample of what their product is, and then you use that in your testing in order to determine whether or not you have the right formula?

Bob: John, that’s a really good point. We’re willing to do enough work that we need more than a sample. We usually look for 20 or 30 of the customer’s components, if possible. In some cases, the components have not been fully designed or developed, or in other cases, the components are very large and costly.

Generally, we’ll look at 12 to 24 evaluations before selecting either from our range of standard products or customizing a standard product or considering developing from scratch.

John: You mentioned being able to change the color of the potting compound. What are some of the other types of variables that can be changed in the potting compound?

Bob: Certainly viscosity. The cure time. Sometimes a slower cure time is important so that the potting material can flow around the components very gradually. In other cases, the process includes heat, for enhancing the curing.
We get into the curing package and really fine tune it, dial in the properties that are needed. Other requirements that are very important are thermal conductivity or fire resistant property or optical clarity.

John: Bob Baker, thanks very much.

Bob: Well, you’re very welcome.

John: For more information, you can visit Key Polymer’s website at or call 978 683 9411.