State of the cure
Each type of resins has its own hardening system:
* Peroxide hardeners or initiators such as dicumyl peroxide, methylethylketone peroxide, benzoyl peroxide, butyl peroctoate.
* Cobalt promoters: naphtanate, octoate…
* Inhibitors such as hydroquinone or benzoquinone used at very low level (50 to 100 ppm) to control pot life and gel time.
* Formaldehyde for phenolics.
* Amines for epoxies, methylenedianiline (MDA)…
The final state of the cure depends on the curing system type, the temperature and the time of curing.
Reinforcement
Fibres, particularly glass fibres, are the most popular reinforcing agents.
Reinforcement increases:
* With fibres nature, in the following order: glass, aramid, carbon.
* With aspect ratio.
* With length. Continuous fibres have the highest effect.
The next two graphs compare:
* Mechanical performances of SMC (thermoset with glass fibre mat) and thermoplastic with glass fibre of millimetre (short GF) and centimetre (long GF) length.