Coagents types

Crosslinking systems based on peroxides are usually simple. Unlike with sulphur vulcanisation systems, the addition of ZnO and stearic acid is not necessary, so crosslinking is achieved in many cases simply using a crosslinking peroxide. However, the addition of a coagent may be useful (see below). In some other cases, a combination of various types of crosslinking peroxides may be suitable. 

Influences of the different methacrylates and 1,2-polybutadiene as coagents on the mechanical and rheological properties of the peroxide-cured PP/EPDM TPVs were reported by Rishi and Noordermeer [39, 40]. They interpreted the results in terms of solubility parameter and cure kinetics. The effects of coagents on both processing and properties of the compound depend on the nature of the polymer, type of peroxide, and other compounding ingredients. Among the methacrylate... 

Representative coagents of this type include triallyl cyanurate and polyallyl ethers and esters. 

A further class of coagents function by a mechanism of the following type ... 

A rheometric study [159] was carried out by different tested poly(VDF-ter-HFP-ter-TFE) terpolymers cured by peroxides [dicumyl peroxide (40%) for P-1 l,3-bis(ferf-butylperoxisopropyl)-benzene (40%) for P-2 l,l-bis(ferf-butylperoxy)-3,3,5-trimethylcyclohexane (40%) for P-3 2,5-bis-(ferf-butyl-peroxy)-2,5-dimethylhexane (45%) for P-4 2,5-bis-(t-butylperoxy)-2,5-di-methylhexyne (45%) for P-5] with the same coagent (TAIC). Table 17 [159] gives the composition of the compounds used in the study. Compounds (FP-l to FP-5) differ only from the type and the amount of the peroxide. 

Peroxide curing systems can be used only with those fluoroelastomers containing a peroxide cure site, for example the low temperature, PMVE containing types, the highly fluorinated types, and other specialty type such as BR 9151 or ETP. Peroxides such as Luperco lOlXL are preferred, in conjunction with TAIC coagent DIAK 7. 

Coagents should be used with the peroxide to obtain a satisfactory rate and state of cure. Commonly used coagents are TAC (triallyl cyanurate), TATM (triallyl trimelli-tate), HVA-2 (iV.M-m-phenylene-dimaleimide), di- or tri-methylacrylates, liquid high 1,2 polybutadiene, diaUyl phthalates, and others. The allylic types provide better process safety and are more effective in CSM. 

When the coagent chosen is sulphur, it is possible to obtain various types of bond by increasing its quantity compared to the peroxide. The bonds... 

Apart from peroxide type and the amount of peroxide incorporated in compounds, the efficiency of crosslinking depends on coagents. The commercially important ones are ... 

Antwerp, Belgium, 22nd-23rd Nov. 1999, paper 13 SELECTING ACRYLIC TYPE COAGENTS FOR HOSE AND BELT APPLICATIONS... 

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