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 silicone or synthetic polymer to a highly elastic state. A post cure is often employed to remove any volatile by-products. A simple and cost effective way of enhancing the mechanical properties is to use a Peroxide Co-Agent, we offer several and can recommend which would be best and how to utilise it for your particular application.
BDBP-TRANS - Bis(2,4-Dichlorobenzoyl)peroxide
Theoretical active oxygen: 4.21%
White paste, 50% in silicone oil
High quality pail liner is used for ease of use and safety. UN pail remains clean and does not need to be disposed of as hazardous waste.
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.
DBPH-50-PSI - 2,5-Dimethyl-2,5-bis(tert-butylperoxy) hexane
50% Active, compounded with fumed silica and silicone oil.
Easier to handle than a liquid when mixing.
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.
DCP - Dicumyl peroxide
Theoretical active oxygen: 5.86%
Fine powder (40% active) or crystalline form (100% active)
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.
We are the exclusive representative of Chinasun Specialty Products, one of the worlds leading manufacturers of peroxide initiators. If you use any peroxides we would be happy to hear from you. We can offer several other peroxides and can compound them however you wish.
PLATINUM CATALYSTS
These catalysts are employed in a by-product free addition hydrosilylation reaction between silanol functional silicones and hydride functional silicones. The clean, by-product free reaction usually takes place at room temperature. We offer several platinum catalysts, including;
Karstedt Catalyst - Platinum Divinyltetramethyldisiloxane Complex
Ashby-Karstedt Catalyst - Platinum Cyclovinylmethylsilane Complex
We can formulate in our labs up to whatever activity you require.
We also offer the necessary reactive silicones, moderators (to slow the reaction down), cross-linkers, stabilisers, and hydrophobic fumed silica.
MODIFICATION AGENTS FOR SILICONES AND SYNTHETIC POLYMERS
Modification of the vinyl base fluids or addition of reactive specific silicone fluids/gums 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 and dispersion agents 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 and vinyl 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.