Epoxy or polyepoxide is a thermosetting epoxide polymer that cures when mixed with a catalyzing agent or "hardener". The process of polymerization is called "curing", can be controlled through temperature and choice of resin and hardener compounds; the process can take minutes to hours.
Resin development is something that we have been doing for over 36 years. Formulating a resin that is super stiff, yet becomes moldable at low temperatures and has a fast cure time is critical for our unique requirement which is why we are probably the only cycle shoe manufacturer who develops our own resins in-house.
Our resin becomes soft at just 60oC (140oF) which is the lowest in the industry. Once you heat the resin, mold the shoe and let it set, it is permanently set without the need to remold. You can also reheat the resin as many times as you like.
The temperature of the air and the amount of humidity are critical in determining the amount of hardener that needs to be added to the resin. That is why we have a computer that mixes the resin and hardener together and dispenses the resin after measuring the air temperature and humidity.
Most manufacturers use a process known in the industry as pre-preg. This is where the resin is "pre-impregnated" into the carbon fiber. In virtually all applications, the resin is chosen by the carbon fiber manufacturer in a one shoe fits all kind of deal. The shoe manufacturer has no way of altering the resin to meet the heat moldablilty requirements of modern shoes and that is why they require very high temperatures to make the shoes slightly heat moldable. Pre-preg manufacturing is fine for bike frames or crank sets that do not need to be heat molded by the rider, but they are unsuitable for the construction of cycling shoes.