Epoxies – Useful info
Single Component Epoxies
Single component epoxies that cure at low temperatures (below 50 degrees C) need to be delivered frozen. These are usually shipped in specially insulated cartons containing « dry ice ». N.B. Most of our two component epoxies can be delivered in ready-to-use syringes.
Moisture inhibits Curing
Water inhibits the curing reaction of all epoxies. This means that humidity present in the air could cause an epoxy to cure more slowly than normal or prevent complete curing. In most cases, humidity in the air doesn’t have any measurable effect. So how does humidity cause problems?
1) If the epoxy is colder than the air temperature, water vapor will condense onto it.
2) If the epoxy is applied as a very thin layer, the surface area-to-volume ratio becomes so great that a significant amount of water can be adsorbed onto its surface.
3) Epoxy hardeners (part B) are hydrophilic. Therefore the container should never be left open for longer than necessary.
The Mix Ratio
The mix ratio defines the proportion of epoxy resin (part A) that should be mixed with the hardener (part B). In most cases, it is best to measure the parts by weight. A mix ratio of 10:1 means 10g part A + 1g part B.
N.B. Although the mix ratio is not critical, variations will result in slightly different end-products. Whereas a mixture containing an excess of part A will still cure, a mixture with an excess of part B may remain soft and appear not to cure! This is actually due to the presence of unreacted part B which acts as a « plasticizer ».
Room Temperature Curing Epoxies
While many Epoxies cure at room temperature, a heat cure step is recommended to achieve optimum properties.
See the complete brochure concerning Low Outgassing.