PEROXIDES INITIATORS


Peroxide Initiators

Free radical coupling of vinyl/hydride functional silicones is initiated with peroxide initiators at elevated temperatures, usually between 140oC and 160oC. A peroxide load of between 0.2-1.0% is typical.

Curing will convert the silicones to a highly elastic state. A post cure is often employed to remove any volatile by-products.

Modification of the vinyl base fluids or addition of reactive specific silicone fluids or silanes can enhance desired characteristics. Properties such as low temperature, high temperature, electrical, enhanced mechanics, radiation, solvent and chemical resistance can all be built into the elastomeric system.

Plasticisers can also be added to lower the viscosity to allow greater ease of handling. Highly cross-linked vinyl and hydride resins can be added to increase the cross-linking density giving an elastomer with greater tear and shear strength.

For highly filled formulations utilising siliceous materials, such as silicas, mercapto silane coupling agents can be employed to give a strong adhesion between the filler and the silicone, this will enhance the mechanical strength of the elastomer.

 

BDBP-TRANS

Bis(2,4-Dichlorobenzoyl)peroxide

Theoretical active oxygen: 4.21%

White paste, 50% in silicone oil

Material bagged for ease of use. UN pail remains clean and does not need to be disposed of as hazardous waste. Can also be supplied directly in the pail with no liner.

 Regularly used in heat cure rubbers, low toxicity, low peroxide hazard and

especially useful in aromatic modified elastomers and silicones. This

peroxide is usually the first choice as it has the lowest activation

temperature and the highest cure rate of the common peroxides, making it ideally suited to fast continuous curing.

Specifically developed for use in making translucent or light coloured silicone elastomers. Can be used in all other silicone formulations. Material is compounded with a small amount of fumed silica to give enhanced mechanical properties of the elastomer.

 

DBPH

2,5-Dimethyl-2,5-bis(tert-butylperoxy) hexane

Theoretical active oxygen: 11.02%

Clear/light yellow oily liquid, with no aromatics, can be used on translucent elastomers as it imparts very little colour.

High oxygen active initiator, with a low volatility. Typically employed in heat cure rubbers including EPDM, silicone and unsaturated polyester systems.

Also supplied compounded with fume silica as a 50% active paste.

 

TBPB

tert-Butylperoxy benzoate

Theoretical active oxygen: 8.24%

Free radical initiator in medium temperature heat cure polymerisation of many monomers and elastomers including silicones, foams, styrene,

acrylics and unsaturated resins.

 

DPO

Dibenzoyl peroxide

Theoretical active oxygen: 6.62%

50% in silicone oil

Free radical initiator in the polymerisation of heat cure rubbers,

styrene, acrylics and unsaturated systems.

 

DCP

Dicumyl peroxide

Theoretical active oxygen: 5.86%

crystalline powder

High oxygen active initiator, typically employed in heat cure rubbers,

including silicones, EPDM and unsaturated polyester systems, such as Monosil and Sioplas. This peroxide is a good compromise between high reactivity and scorch reduction at medium curing rates.

 

TMCH

1,1-Bis(tert-Butylperoxy)-3,3,5-trimethyl cyclohexane

Theoretical active oxygen: 10.58%

Colourless to slight yellow oily liquid

Also supplied as a 75% active solution in isododecane.

High oxygen active initiator, typically employed in heat cure rubbers,

including silicones, EPDM, styrene and unsaturated polyester systems, such as Monosil and Sioplas. This peroxide has a high reactivity at lower curing temperatures, this allows a faster throughput  or lower curing

temperatures.

 

BCH

1,1-Bis(tert-Butylperoxy) cyclohexane

Theoretical active oxygen: 12.31%

Colourless to slight yellow oily liquid

High oxygen active catalyst, typically employed in heat cure rubbers,

including silicones, EPDM, styrene and unsaturated polyester systems, such as Monosil and Sioplas.

 

DBP

Di-tert-butylperoxide

Theoretical active oxygen: 10.94%

Colourless to slight yellow oily liquid

High oxygen active dialkyl initiator, typically employed in the

 polymerisation of olefins and acrylics.

 

BUP

tert-Butylcumyl peroxide

Theoretical active oxygen: 7.68%

Clear Oily Liquid

Free radical initiator used in the polymerisation of natural and synthetic heat cure rubbers and polyolefins.

  

 

 

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