F40M-SP (SP technology) and F40P-SP2 (SP2 technology) were compared to F40KE (standard peroxide) for crosslinking EPDM (see Table 7 and Figures 6 and 7). F40P-SP2, 7.20 phr, provides a significant 43% increase in ts2 scorch time at 177°C (350°F) versus F40KE, 6.26 phr.  F40M-SP, 6.26 phr, provides a 15% increase in ts2 scorch time at 177°C. These “SP” and “SP2” peroxides provide the same tc90 cure time as F40KE, i.e., there is no adverse effect on productivity due to the increased scorch time.

F40P-SP2 provides more than double the scorch time protection in EPDM compared to F40M-SP. Despite the low Mooney viscosity of Vistalon 2504 EPDM, F40M-SP and F40P-SP2 provide 10% lower minimum torque (M_L) or viscosity versus F40KE, when curing at 177°C. This lower EPDM viscosity is due to the scorch protection technology provided by these peroxide formulations. The combination of a lower EPDM viscosity with a longer scorch time makes it easier to completely fill the mold during injection, compression or transfer molding operations.

Compounding EPDM at 138°C using 6.26phr F40M-SP or 7.20phr F40P-SP2 provided a 40% and a 130% increase in ts2 scorch time respectively, versus the 6.26 phr F40KE control.  Please refer to Table 8 and Figure 8.  Several well-known companies[i] in the USA and Europe have successfully transitioned from a two-pass to a one-pass EPDM compounding operation simply by replacing F40KE with F40M-SP.  We expect the new F40P-SP2 peroxide to offer an even wider processing window for compounding EPDM, based on our results described above.

In summary, F40P-SP2 is highly recommended for molding larger and/or more intricately crosslinked EPDM components.  F40M-SP and F40P-SP2 provide enhanced mold filling while minimizing hot-tear and scrap issues that reduce productivity and profits when molding crosslinked EPDM.  A wider processing window is available for compounding EPDM when using the SP2 peroxide technology.