At the same time, higher thermal stability of PMTO results the formation thermally stable radicals which gives higher state of cure in case of PMTO-cured PDMS.
This again indicates that, with rise of temperature from 180[degrees]C to 200[degrees]C, the thermal stability of (DCP + TEMPO) mix decreases that results reduction in the gel content and increase of percentage swelling of the compound whereas, at high temperature PMTO shows better effect from both perspective point of view.
The above physicomechanical behavior infers that, at high temperature even in presence of TEMPO also, the crosslinking efficiency of DCP is poor than that of PMTO.
Even with the rise of temperature from 180[degrees]C to 200[degrees]C, the crosslinking efficiency of (DCP + TEMPO) mix is getting reduced to some extent, whereas the crosslinking efficiency of PMTO increases at higher temperature which results the formation of higher degree of crosslinks network for PMTO-crosslinked PDMS and this leads to the improvement in mechanical properties in case of PMTO-crosslinked PDMS.
In case of PMTO, crosslinking efficiency rather increases at higher temperature that results higher degree of crosslinked network and it provides higher thermal stability.
This phenomenon again supports the fact that at higher temperature crosslinking efficiency of DCP reduces even in presence of TEMPO also, whereas crosslinking efficiency of PMTO got increased at higher temperature.
It can be clearly noticed from the figure that, in terms of tensile strength, elongation at break point of view, TPV developed by PMTO peroxide is superior compared to the TPV developed by (DCP + TEMPO) mix.
Two different peroxides namely DCP and PMTO having different chemical structures have been investigated to crosslink the PDMS rubber.
Although the presence of TEMPO nitroxide increases the scorch safety of (DCP + TEMPO)-crosslinked PDMS, PMTO was found superior for the crosslinking of PDMS at higher temperature (>180[degrees]C) regarding crosslink density, mechanical properties, thermal stability, and dynamic mechanical behavior point of view.
Cure curves of PDMS, crosslinked by PMTO (a) at 180[degrees]C and (b) at 200[degrees]C.
Crosslink density of PDMS crosslinked by (DCP + TEMPO) and PMTO.
a) Swelling index and (b) gel content of PDMS crosslinked by (DCP + TEMPO) and PMTO.