Pot life refers to the resin’s application window and is an indicator of its basic reactivity. It is the time during which the hardener/resin mixture is still processable and is determined by the cross-linking reaction rate, which also influences the curing time until complete polymerisation.
Pot life / application time
The pot life of a resin corresponds to the material’s application time and thus the time window in which the user can apply the material and process it with a metering system. Within this window the reaction of the material has not advanced enough for its flow characteristics and surface adhesion to be seriously impaired. This pot life is usually agreed between the material manufacturer and the customer, taking into account the manufacturing process. Since pot life is also defined differently by different manufacturers, it cannot always be directly compared.
Since gel time is often directly related to pot life, it also defines the end of the application window. Jointing is no longer possible once the gel time has expired. Gel time is often confused with pot life.
Handling time is usually the most important time for the customer. After this period of time, the reaction of the resin mixture has progressed enough for the next process step with the potted or bonded part to take place. Since the next process step can be very different, the handling time must always be defined in a discussion between the customer and the manufacturer.
In many cases parts are placed on a blister pack or actually handled at the end of the handling time. If the parts fall from the belt after reaching the specified handling time (particularly during large-scale production), the reaction must be allowed to proceed further for the material to achieve a certain hardness. The handling time can be directly influenced by adjusting the reactivity of the resin. Temperature-controlled curing processes can also shorten the handling time, which may also be affected by the component’s geometric features, such as variations in thickness, and the surrounding materials (e.g. metal).
The final chemical cure is achieved after a period of 7 to 14 days at room temperature (22 °C) or 24 hours at 80 °C, depending on the polymer system. Hot curing systems are different since they require defined temperature control to achieve full cure. Final chemical cure is often not the objective in an industrial production process, and many components achieve only 90–95 % cure at the end of the production curing process. The remaining unreacted functional groups react during installation or on the way to the end customer.