Post Cure
Photo Credit: Cuda built by Z Rodz and Customs. Photography by McGaffin Photography for Wheel Hub Magazine.
Achieving optimal physical properties in your epoxy components often requires post-curing – controlled heating after the initial cure stage. Let’s delve into the specifics:
Understanding Post-Curing
Certain resin/hardener combinations, such as LAM-249-HT, INF-249-HT, LAM-239 and HTP variants, require an elevated-temperature post-cure for peak performance. Post-curing enhances physical strength and thermal properties beyond what’s achievable with room-temperature cures alone.
Determining Post-Cure Schedules
Each resin/hardener combination has unique post-cure requirements to unlock 100% of its potential properties. Published properties won’t be reached if post-cure temperatures fall below specified levels. Establish post-cure schedules based on desired physical properties, equipment limitations, and material tolerances.
Executing Post-Cure
During post-cure, gradually raise the part’s temperature to the target, hold it, and then slowly cool it. To avoid thermal shock, increase temperatures gradually and don’t exceed maximum thresholds. The post-cure schedule dictates the maximum potential properties achievable.
Recommended Post-Cure Guidelines
Follow these guidelines for optimal post-curing:
PRO-SET® Laminating and Infusion Epoxies
- Increase the temperature from room temperature by 8°–11°C (15°–20°F) per hour.
- At every 22°C (40°F) increase in temperature, hold that temperature for an extra hour to allow internal laminate temperatures to equalise. Resume the temperature increase of 8°–11°C (15°–20°F ) per hour.
- Continue this cycle until the post-cure temperature is reached.
- Hold the temperature as indicated on the resin/hardener data sheet.
- Decrease the temperature at a rate of 11°C (20°F) per hour.
- Hold at 35°C (95°F) for two hours to allow for normalisation.
- Turn off heat and allow to cool to room temperature. This schedule is recommended when curing a lighter laminate. The temperature ramp speed should be decreased for moulds, plugs, and heavy laminates. We recommend building test panels of the finished laminate schedule to determine the ideal post-cure cycle. Thermocouple wires embedded in the test laminate will measure the temperature lag during the post-cure.
PRO-SET® High-Temperature Epoxies
- Increase the temperature from room temperature at a rate of 12°F (7°C) per hour.
- Hold at 140°F (60°C) for 2 hours to allow internal laminate temperatures to equalize. Resume the temperature increase of 12°F (7°C) per hour.
- Hold the temperature as indicated on the resin/hardener data sheet [275°F (135°C)].
- Decrease the temperature at less than 20°F (11°C) per hour.
- Hold at 95°F (35°C) for two hours to allow for normalization.
- Turn off heat and allow to cool at room temperature. The schedule is recommended for curing a lighter laminate. The temperature ramp speed should be decreased for molds, plugs, and heavy laminates. We recommend building test panels for the finished laminate schedule to determine the ideal post-cure cycle. Thermocouple wires embedded in the test laminate will measure the temperature lag during post-cure.
Heating Methods
Various heating methods are available, from insulated ovens to radiant heaters. However, radiant heating may lead to uneven curing and laminate print-through, so caution is advised.
Post-Curing in Moulds
Moulds should be post-cured at temperatures exceeding those required for finished parts to prevent distortion. Similarly, plugs used in mould construction should be post-cured at higher temperatures to maintain fairness.
Adhering to these guidelines and considering specific resin/hardener combinations can achieve optimal post-cure results, ensuring the highest quality in your epoxy components. Consult the respective Technical Data Sheets for detailed instructions tailored to your products.
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