Efficiently Applying, Processing and Curing Epoxy Resin
Epoxy resins are reactive resins with which a stable, chemical-resistant plastic can be produced through the addition of additives. Epoxy-based casting resins feature excellent electrical properties and a high hardness level. When applying epoxy with the proper metering equipment from a manufacturer, however, it is important to watch out for heat generation during curing.
Epoxides (EP) are an important and multipurpose material class. The name comes from the reactive group included in the reaction, the so-called epoxide group or oxirane group. Adding suitable hardeners to epoxy resins can produce a stable, thermosetting resin with high chemical resistance. These widely distributed epoxy-based structural adhesives are also used for corrosion protection or as a PCB material. As casting resins, epoxides are frequently used to insulate and protect sensitive electronic or electrical components such as ignition coils, capacitors and commutators.
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Epoxy resin: properties
In their cured state, epoxy casting resins usually feature a very high level of hardness and mechanical stability, excellent electrical properties and exceptionally good adhesion to almost all substrates. Additional advantages include low flammability, high glow heat resistance and excellent temperature stability. Epoxy resin properties can be significantly modified using suitable fillers and additives. Fillers such as aluminum hydroxide act as flame retardants, hollow glass beads lower the density, and silica sand improves abrasion resistance. Even material shrinkage during the curing process can be prevented using the right fillers.
Compared to other casting resins such as polyurethane, the excellent properties of epoxy resins are reflected in a higher price to a certain extent. For the user, the high heat generation during hardening must be taken into account, since this can cause faults in sensitive assemblies. To prevent high temperatures from occurring, larger quantities of material can be applied over several passes. In addition, when potting epoxy resins, it is important to note their usually high viscosities.
TIP: To achieve higher dimensional stability under heat and complete cross-linking, the epoxy resin can be subjected to additional heat curing after standard curing.
The mixed epoxy resin can be applied easier at the right temperature. In this case, however, the rule of thumb is that the pot life is usually halved with a 10°C increase in temperature.
Epoxy resin: processing and application
Epoxy-based casting resins are usually delivered in two components that have to be mixed together before potting. The A component usually contains the epoxy resin and the B component contains the hardener, which is added to the resin in a specific mixing ratio. If this ratio is not precise, there is the risk that the material properties will be deficient and ultimately the product will be wasted. The working life of reactive materials is known as pot life. The pot life of epoxy resins ranges from a period of a few minutes to several hours. It is important to note that the viscosity of the resin increases non-linearly during the pot life. From a certain point in time, the viscosity increases rapidly and the epoxy resin can then only be processed and applied with great difficulty. The ability to process the mixed resin can be improved by heating it; however, this results in a shortened pot life.
- For efficient and reliable processing of epoxy potting compounds, Scheugenpflug offers the LiquiPrep LP804 preparation and feed system. Its temperature control function makes it possible to control the viscosity of the epoxy.
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- If epoxy resins are to be used to pot electric coils such as ignition coils, the material must be prepared and dispensed in a vacuum to ensure bubble-free encapsulation of the workpiece. Scheugenpflug offers different vacuum potting systems for these applications as well: from the entry level model to the high performer.
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