Epoxy resin taking longer to cure

Epoxy resin taking longer to cure

Why is my epoxy project taking longer to fully cure?

Epoxy resin taking longer to cure.Before going any further, let me give you the definition of a “THERMOSEL RESIN”:  A thermosetting resin, often called a thermoset, is a polymer that is irreversibly hardened by curing from a viscous liquid prepolymer or resin. Curing is induced by heat (exotherm) when mixing resin (part A) to a hardener (B). We put emphasis here on CURING IS INDUCED BY HEAT (EXOTHERM). This means that if the reaction between the parts A and B is reduced by cold, the curing process as well. If it occurs, the set time (polymerization) will take longer. Because there is less energy for the molecules to link to itself by a covalent link.  

The colder the temperature is in the room, the longer the resin takes to fully cured.

Cold also has an incidence on the viscosity of the resin.  The colder it is, the higher the viscosity will be.  Keep also in mind that if you work in a cold environment less than 22°C the curing process will be slowed down. 

Every 1°C/F less than 22°C/72F will slow down the curing process by an approximate 10%. Don’t minimize this important factor when using our CHILL EPOXY™ products.  

Epoxy Resin Taking Longer to Cure

  • Temperature of the product in the containers (if lower than 22°C, it will slow down the curing process. (Every 1°C below 22°C will affect the curing time of an approximate 10%). 
  • Precision of the mixing ratio in volume or weight. (If the ratio is not precise, it will avoid the resin to reach its total cure and maximal hardness which can result in soft or flexible epoxy. Follow the instructions. All TDS and instruction sheets can be downloaded on our Resin Technical Center.
  • Homogeneity of the mix A/B (if not totally homogeneous, again, it will stop the resin to reach its total cure).  
  • Thickness of the pour (If you pour less than the recommendation, the exothermic reaction will not reach its objective and the lack of energy will avoid the resin to cure within the recommended curing time of 7 days at 22°C.   
  • If the temperature of the working area is lower than 22°C/72F, it will slow down the curing process.  Each C/F under 22°C/72F will have an impact on the duration of the curing process.
  • Demolding too fast. If the epoxy hasn’t reached its final harness yet, or is being demolded before the final cure (7days), the epoxy could be flexible or soft. 
  • Design of the pour (length x width x thickness). The mass and dimensions will have an impact on the curing process.

For example: A 30L pour with the CHILL ICE 2 ( casting epoxy) will cure faster than a 15L pour with the same product. Same thing with a 2″ thick project versus 1″ thick.

Another way to know if the epoxy has reached its final cure is using a durometer. ( See image below) which will indicate the hardness of the resin. Because we know our epoxy solutions will reach a specific hardness and you can verify the hardness of your pour on a daily basis and demold only when it reaches its final hardness.  

DUROMETER SHORE D