Platinum vs Peroxide Curing: Which Silicone Rubber Is Right for Your Industry?

 Silicone Curing: Types, What to Choose according to your Industry?

In Silicone Rubber chemistry majorly 5 types of curing happen

• Addition Curing using Platinum Catalyst
• Free Radical Curing using peroxide
• Condensation Curing using Tin like Catalyst
• Moisture Curing using Acetoxy, Alkoxy etc.
• UV Curing using UV Light

In this article we will explain the benefits of each curing system and how it helps on selecting the product for different applications. Our Major Focus area will be Platinum based, Peroxide based Curing which is majorly used in the fabrication of silicone rubber.

Platinum catalyst based curing is chemical reaction used by Hydrosilylation where vinyl groups in the rubber and silane hydrides react in presence of platinum catalyst to do cross linking.

Si–H + CH₂=CH–Si —Pt→ Si–CH₂–CH₂–Si

The hydride molecule will connect many vinyl-silicone chains in the presence of platinum, causing an addition reaction, the major factors contribute the reaction is the hydride, vinyl, platinum content and the temperature. The beauty of the reaction is that it will not create any by product after the reaction and leave platinum inside. You can refer the reaction and no byproducts is formed, the platinum will be in the range of ppm and it get entrapped with the cured silicone thus even the catalyst too will not be left out.

In Peroxide Curing free radicals generated during heating of the peroxide causes the crosslinking of silicone

RO–OR → 2 RO· (free radicals)

RO· + –Si–CH₃ → ROH + –Si–CH₂·

–Si–CH₂· + ·CH₂–Si– → –Si–CH₂–CH₂–Si–

As you can see ROH will be the byproduct in form of miner alcohols, ketones, acids or minor organics. The Byproduct produced during the reaction will be removed by postcuring where the peroxide cured will be heated to 150-200 degree C for 4 hours with the supply of fresh air, this helps in removing all by products and increases the crosslinking. A minor shrinkage will be also there due to the chemical reactions.

Other Curing like condensation, UV, electron beam like curing is also possible which are not used in fabricating our special parts. Although special compounds or speciality formulations can be made using the condensation/UV curing chemistry it needs special encapsulated controlled environments and areas.

Now comes the selection criterion for what silicone rubber and curing should be chosen.

As you can see peroxide cured silicone rubber generates some minor by products which causes minor odour or smell, some contaminants if not properly post cured and may reduce the transparency too, a bit like traces of yellowing on unscientific post curing.

In Platinum cured systems contaminants can alter the curing, should be processed carefully as pre curing can happen on the mixing, resting stages. The Cost of the curing agents, handling cost makes the process and product costlier but will not produce any by products. Difficulty of storage of the mixed materials and unskilled personnel increases the risk of material loss.

We Centroid is aware of the curing technology in the molecular wise and kept our premises, personnel, infrastructure suitable for both. We have aligned our production process, systems in line to the requirement and try to communicate the same with the customer. A complete customer statement is collected, processed and shared with the customer after understanding their application of use, their cost budgets with prototypes. This reduces the development time to half, removes multiple trials and makes the process smoother.

Platinum cured products can be chosen for a stricter medical, pharmaceutical purpose where the system demands such a requirement and peroxide cured can be chosen for a more industrial related purpose where the processing cost demands that. The Basic properties like temperature and other properties of the rubber remain unaffected even on both curing systems.

Consult the expert manufacturer with your problem statement, designs today itself.