Recently, rubbers are found to be reinforced by adding a high loading of zinc dimethacrylate (ZDMA) without fillers.
There also have been some literatures reported about dynamically vulcanized PP/EPDM with ZDMA in the presence of peroxide, de Risi and Noordermeer  evaluated (meth)acrylate coagents with peroxide in PP/EPDM and found that more stable free radicals were formed by positioning of the radical on the coagent molecule.
Among the peroxide cured samples, ZDMA having labile ionic crosslinks undergoes the highest permanent set, yet it is 50% lower than the sulfur cured samples.
Among the peroxide-coagent compounds, a relative ranking of storage modulus is observed: ZDMA > PER > PDM > TMA.
Metal salts of unsaturated carboxylic acids, especially zinc dimethacrylate (ZDMA
), are originally used as coagents for peroxide curing rubbers.
In the current formulation, Type I coagents represented are trimethylolpropane trimethacrylate (TMPTMA), zinc dimethacrylate (ZDMA
), and N,N'-m-phenylene dimaleimide (PDM).
In a third experiment, a series of stocks was evaluated where the activation was accomplished using zinc stearate at 5 phr or zinc dimethacrylate (ZDMA
) at 15 phr.
Figure 10 demonstrates the improvement in aged tear strength (ASTM D 624) when ionic crosslinks are formed using zinc salts (ZDA and ZDMA
) compared to a traditional triacrylate coagent (TMPTA) (ref.
Hydrogenated nitrile butadiene rubber (HNBR)/zinc dimethacrylate (ZDMA
) blends have been available for many years now, and the improved mechanical properties that are offered are well recognized within certain areas of the rubber industry, such as belting, roller covering and the oil industry.
The metallic coagents discussed in this article are zinc diacrylate (ZDA) and zinc dimethacrylate (ZDMA
Table 2 - comparison of zinc salts Formulation (phr) HNBR (<0.5% RDB) 100 100 Zinc di-methyacrylate (ZDMA
) 35 Zinc di-acrylate (ZDA) 35 [alpha], [alpha]'bis (t-butlperoxy)- 5 5 -diisopropylbenzene [40% active] Stress/strain Tensile strength (MPa) 20.7 27.7 Modulus at 100% elong.
Zinc diacrylate (ZDA) and zinc dimethacrylate (ZDMA
) are the difunctional salts of their respective acids.