What can cause epoxy resin to crack once cured?

Epoxy resin can crack once cured for several reasons, which are often related to improper handling, curing conditions, or formulation issues. Here are some common factors that can lead to cracking:  Improper Mixing Ratios: Epoxy resins typically require precise measurements of resin and hardener. If the mixing ratios are incorrect, it can result in an incomplete or uneven curing process, leading to weak spots and cracks in the finished product. Excessive Heat Generation: Some epoxy resins can generate heat during the curing process. If the heat is not dissipated properly or the epoxy is applied in too thick of a layer, it can cause uneven curing and lead to cracking. Moisture Contamination: Moisture or humidity can interfere with the curing process of epoxy resins. If the epoxy is exposed to moisture during curing, it may not fully harden, leading to cracks and reduced mechanical properties. Inadequate Surface Preparation: Proper surface preparation is crucial for good adhesion of epoxy resins. If the surface is not cleaned, degreased, or sanded adequately, the epoxy may not bond properly, resulting in cracks and delamination. Incompatibility with Substrate: Some epoxy resins may not be compatible with certain substrates or coatings. When incompatible materials are used together, they can contract or expand differently during curing, leading to cracking. Curing Temperature and Time: Epoxy resins typically have recommended curing temperatures and times. If these parameters are not followed correctly, it can affect the degree of cross-linking and result in weak points and cracks. Overheating during Curing: Subjecting epoxy resin to high temperatures during curing can accelerate the process, but it can also lead to excessive shrinkage and cracking. Volatile Solvents or Air Bubbles: If there are volatile solvents present in the epoxy formulation or trapped air bubbles during the mixing process, they can create weak points in the cured epoxy, leading to cracking. Thermal Expansion and Contraction: Epoxy resins have specific coefficients of thermal expansion. If the cured epoxy is exposed to significant temperature changes, it may expand or contract beyond its capacity, leading to cracks. Download PDF here