Crosslinking EVA
Below is a table of RPA (Alpha Technologies) Rheometer data comparing the performance of three different organic peroxides that possess significantly different thermal decomposition activity. These liquid, room temperature stable, organic peroxides are Luperox^® 101, Luperox^® TBEC and Luperox® 231 and are listed in order of decreasing thermal stability. Of the three, Luperox^® 101 is the most thermally stable and belongs to the Dialkyl class of peroxide. Luperox^® TBEC is a monoperoxy-carbonate type of peroxide, and Luperox^® 231 is the fast decomposing peroxyketal class of peroxide.

The concentrations of these peroxides were adjusted to provide relatively the same level of crosslinking, based upon MH or maximum torque in deciNewton-meters (dN-m). When evaluating these peroxides at a constant temperature of 160°C, we see that the time to attain 90% of the final cure is quite long for Luperox® 101 as compared to Luperox^® TBEC. Clearly Luperox® 231 is the fastest curing, but more product must be used on a weight basis as it generates a combination of high energy and lower energy radicals. For that reason, it is less efficient than Luperox^® TBEC. Of the three peroxides, Luperox^® TBEC offers the best balance of thermal stability when compounding, along with good crosslinking efficiency and a short cure time when crosslinking. Note that the Evatane^® EVA resin used below was crosslinked as supplied. No fillers, stabilizers or antioxidants were added to the EVA resin.

PHR Used		0.756 phr	1.50 phr	2.75 phr
Peroxide Used:		Luperox® 101	Luperox® TBEC	Luperox® 231
EVA Compound		Evatane® 33-45	Evatane® 33-45	Evatane® 33-45
Cure Temperature (°C)		160°C	160°C	160°C
S'@ Max S'(MH)	dN-m	6.15	6.95	5.85
S'@ Min S'(ML)	dN-m	0.036	0.071	0.10
ts0.4scorch time min		1.3	0.48	0.35
Time@ 90% cure min		22.43	4.37	2.05

Mechanisms of EVA

Mechanisms of Crosslinking - General

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