As can be seen, this FEPM recipe is much more sensitive to the specific coagent used than other recipes.
* VTA is more sensitive to changes that occur at the onset of cure, especially with the peroxide cured halogenated elastomers (such as CPE and FEPM) in that not only the scorch time can be measured, but the VTA scorch temperature as well.
1 2 3 4 5 6 Phr Masterbatch 236 236 236 236 236 236 Di-Cup 40KE 7.5 7.5 7.5 7.5 7.5 7.5 TMA 5 HVPBD 5 PBDDA 5 PDM 5 TAC 5 Total 243.5 248.5 248.5 248.5 248.5 248.5 Table 5 - changes in coagents in FEPM compounds MB401 Internal mix Phr Aflas 150P 100 MT 990 carbon black 25 Sodium stearate 1 Total 126 Mill mix Compound no.
The fully saturated materials (EVM, CM, CSM, FEPM) are listed last.
Certain grades of fluoroelastomers may utilize cure site monomers or have reactive groups added to the polymer structure to promote crosslinking with peroxides (FEPM) (refs.
In EVM and FEPM, the Type II coagent produced higher delta torque than the Type I coagents.
(Meth)acrylate esters have not been shown to be as effective in FEPM grades.
FEPM was compounded using proprietary in-house technology.
FEPM reaches equilibrium after the same time period (7.5% drop in compressive stress between 500 and 3,000 hours).
FEPM is beginning to stabilize after 504 hours and remains at a virtual plateau through 4,000 hours of aging (2.6% drop in compressive stress between 500 and 4,000 hours).
Testing of FKM was discontinued after 168 hours while the FEPM reaches a plateau after approximately 500 hours and remains nearly flat through 4,000 hours (6.3% drop in compressive stress between 500 and 4,000 hours).
Candidate elastomers not subject to dehydrofluorinations are Aflas (FEPM
) from 3M or VT-R-6279 from Du Pont.